Category Archives: Low-Carb Diets - Page 2

High LDL on Paleo Revisited: Low Carb & the Thyroid

One of the more mysterious conditions afflicting low-carb Paleo dieters has been high serum cholesterol. Two of our most popular posts were about this problem: Low Carb Paleo, and LDL is Soaring – Help! (Mar 2, 2011) enumerated some cases and asked readers to suggest answers; Answer Day: What Causes High LDL on Low-Carb Paleo? (Mar 4, 2011) suggested one possible remedy.

On the first post, one of the causes suggested by readers was hypothyroidism – an astute answer. Raj Ganpath wrote:

Weight loss (and VLC diet) resulting in hypothyroidism resulting in elevated cholesterol due to less pronounced LDL receptors?

Kratos said “Hypothyroidism from low carbs.” Mike Gruber said:

I’m the guy with the 585 TC. It went down (to 378 8 months or so ago, time to check again) when I started supplementing with iodine. My TSH has also been trending up the last few years, even before Paleo. So hypothyroidism is my primary suspect.

Those answers caused me to put the connection between hypothyroidism and LDL levels on my research “to do” list.

Chris Masterjohn’s Work on Thyroid Hormone and LDL Receptors

Chris Masterjohn has done a number of blog posts about the role of LDL receptors in cardiovascular disease. His talk at the Ancestral Health Symposium was on this topic, and a recent blog post, “The Central Role of Thyroid Hormone in Governing LDL Receptor Activity and the Risk of Heart Disease,” provides an overview.

His key observation is that thyroid hormone stimulates expression of the LDL receptor (1). T3 thyroid hormone binds to thyroid hormone receptors on the nuclear membrane, the pair (a “dimer”) is then imported into the nucleus where it acts as a transcription factor causing, among other effects, LDL receptors to be generated on the cell membrane.

So higher T3 = more LDL receptors = more LDL particles pulled into cells and stripped of their fatty cargo. So high T3 tends to reduce serum LDL cholesterol levels, but give cells more energy-providing fats. Low T3, conversely, would tend to raise serum cholesterol but deprive cells of energy.

Other Pieces of the Puzzle

Two other facts we’ve recently blogged about help us interpret this result:

We can now assemble a hypothesis linking low carb diets to high LDL. If one eats a glucose and/or protein restricted diet, T3 levels will fall to conserve glucose or protein. When T3 levels fall, LDL receptor expression is reduced. This prevents LDL from serving its fat transport function, but keeps the LDL particles in the blood where their immune function operates.

If LDL particles were being taken up from the blood via LDL receptors, they would have to be replaced – a resource-expensive operation – or immunity would suffer. Apparently evolution favors immunity, and gives up the lipid-transport functions of LDL in order to maintain immune functions during periods of food scarcity.

High LDL on Low Carb: Good health, bad diet?

Suppose LDL receptors are so thoroughly suppressed by low T3 that the lipid transport function of LDL is abolished. What happens to LDL particles in the blood?

Immunity becomes their only function. They hang around in the blood until they meet up with (bacterial) toxins. This contact causes the LDL lipoprotein to be oxidized, after which the particle attaches to macrophage scavenger receptors and is cleared by immune cells.

So, if T3 hormone levels are very low and there is an infection, LDL particles will get oxidized and cleared by immune cells, and LDL levels will stay low. But if there is no infection and no toxins to oxidize LDL, and the diet creates no oxidative stress (ie low levels of omega-6 fats and fructose), then LDL particles may stay in the blood for long periods of time.

If LDL particles continue to be generated, which happens in part when eating fatty food, then LDL levels might increase.

So we might take high LDL on Paleo as a possible sign of two things:

  • A chronic state of glucose deficiency, leading to very low T3 levels and suppressed clearance of LDL particles by lipid transport pathways.
  • Absence of infections or oxidative stress which would clear LDL particles by immune pathways.

The solution? Eat more carbs, and address any remaining cause of hypothyroidism, such as iodine or selenium deficiency. T3 levels should then rise and LDL levels return to normal.

Alternatively, there is evidence that some infections may induce euthyroid sick syndrome, a state of low T3 and high rT3, directly. And these infections may not oxidize LDL, thus they may not lead to loss of LDL particles by immune pathways. So such infections could be another cause of high LDL on Paleo.

Gregory Barton’s Experience

Gregory Barton is an Australian, 52 years old, living in Thailand, where he keeps goats, makes goat cheese and manages a large garden which can be seen on

Gregory left a comment with an intriguing story, and I invited him to elaborate in a post. Here’s Gregory’s story. – Paul

Gregory’s Writing Begins Here

One of the claims of low carb dieting is that it will normalize the symptoms of metabolic syndrome. Blood pressure, blood sugar and blood lipids, it is claimed, will all come down on a low carb diet, in addition to weight. For most people this happens. But there is a significant minority of people on Paleo and other low carb diets whose blood lipids defy this claim. (See the list of low-carb celebrities with high LDL in this post.)

Why should this happen? Why should some people’s lipids fall on low carb while other people’s lipids rise? Suboptimal thyroid might be the proximate cause for lipids rising on a low carb or paleo diet. Broda Barnes and Lawrence Galton have this to say about thyroid disorders:

“Of all the problems that can affect physical or mental health, none is more common than thyroid gland disturbance. None is more readily and inexpensively corrected. And none is more often untreated, and even unsuspected.”  — Hypothyroidism: The Unsuspected Illness

I went very low carb in April in an effort to address metabolic issues, eating as little as 15grams carbohydrate per day. I had great results with blood pressure, sleeping, blood sugar and weight loss. But lipids bucked the trend.

I had expected triglycerides and cholesterol to drop when I cut the carbs, but they did the opposite: They surged. By July my total cholesterol was 350, LDL 280, and triglycerides bobbed around between 150 and 220.

I did some research and found several competing theories for this kind of surge:

  1. Saturated fat: The increase in saturated fat created a superabundance of cholesterol which the liver cannot handle. Also, Loren Cordain has claimed that saturated fat downregulates LDL receptors.
  2. Temporary hyperlipidemia: The surge in lipids is the temporary consequence of the body purging visceral fat. Jenny Ruhl has argued that within a period of months the situation should settle down and lipids should normalize.
  3. Hibernation: The metabolism has gone into “hibernation” with the result that the thyroid hormone T4 is being converted into rT3, an isomer of the T3 molecule, which prevents the clearance of LDL.
  4. Malnutrition: In March, Paul wrote that malnutrition in general and copper deficiency in particular “… is, I believe, the single most likely cause of elevated LDL on low-carb Paleo diets.”
  5. Genetics: Dr. Davis has argued that some combinations of ApoE alleles may make a  person “unable to deal with fats and dietary cholesterol.”

I could accept that saturated fat would raise my cholesterol to some degree. However, I doubted that an increase in saturated fat, or purging of visceral fat, would be responsible for a 75% increase in TC from 200 to 350.

There are two basic factors controlling cholesterol levels: creation and clearance. If the surge was not entirely attributable to saturated fat, perhaps the better explanation was that the cholesterol was not being cleared properly. I was drawn to the hibernation theory.

But what causes the body to go into hibernation? According to Chris Masterjohn, a low carb diet could be the cause. Although he does not mention rT3, he warns,

“One thing to look out for is that extended low-carbing can decrease thyroid function, which will cause a bad increase in LDL-C, and be bad in itself. So be careful not to go to extremes, or if you do, to monitor thyroid function carefully.”

If low carb is the cause, then higher carb should be the cure. Indeed, Val Taylor, the owner of the yahoo rT3 group, commented that “it is possible that the rT3 could just be from a low carb diet.” She says, “I keep carbs at no lower than 60g per day for this reason.”

Cortisol and Getting “Stuck” in Hibernation

So what about temporary hyperlipidemia? Bears hibernate for winter, creating rT3, but manage to awaken in spring. Why should humans on low carb diets not be able to awaken from their hibernation? There are many people who complain of high cholesterol years after starting low carb.

A hormonal factor associated with staying in hibernation is high cortisol. It has been claimed that excessively high or low cortisol, sustained over long periods, may cause one to get “stuck” in hibernation mode. One of the moderators from the yahoo rT3 group said:

High or low cortisol can cause rT3 problems, as can chronic illness. It would be nice if correcting these things was all that was necessary. But it seems that the body gets stuck in high rT3 mode.

James LaValle & Stacy Lundin in Cracking the Metabolic Code: 9 Keys to Optimal Health wrote:

When a person experiences prolonged stress, the adrenals manufacture a large amount of the stress hormone cortisol. Cortisol inhibits the conversion of T4 to T3 and favours the conversion of T4 to rT3. If stress is prolonged a condition called reverse T3 dominance occurs and lasts even after the stress passes and cortisol levels fall. (my emphasis)

What I Did

First, I got my thyroid hormone levels tested. A blood test revealed that I had T4 at the top of the range and T3 below range. Ideally I would have tested rT3, but in Thailand the test is not available. I consulted Val Taylor, the owner of the yahoo rT3 group, who said that low T3 can cause lipids to go as high as mine have and, “as you have plenty of T4 there is no other reason for low T3 other than rT3.”

I decided to make these changes:

  1. Increase net carbs to ~50 grams per day. Having achieved my goals with all other metabolic markers I increased carbs, taking care that one hour postprandial blood sugar did not exceed 130 mg/dl.
  2. Supplement with T3 thyroid hormone.
  3. In case the malnutrition explanation was a factor, I began supplementing copper and eating my wife’s delicious liver pate three times per week.

I decided to supplement T3 for the following reasons:

  • The surge in TC was acute and very high. It was above the optimal range in O Primitivo’s mortality data.
  • I increased carbs by 20-30g/day for about a month. TC stabilized, but did not drop.
  • The rT3 theory is elegant and I was eager to test my claim that the bulk of the cholesterol was due to a problem with clearance rather than ‘superabundance’.

What happened?

I started taking cynomel, a T3 supplement, four weeks ago. After one week triglycerides dropped from 150 to 90. After two weeks TC dropped from 350 to 300 and after another week, to 220. Last week numbers were stable.

Based on Paul’s recent series on blood lipids, especially the post Blood Lipids and Infectious Disease, Part I (Jun 21, 2011), I think TC of 220 mg/dl is optimal. As far as serum cholesterol levels are concerned, the problem has been fixed.

I believe that thyroid hormone levels were the dominant factor in my high LDL. Saturated fat intake has remained constant throughout.

My current goal is to address the root causes of the rT3 dominance and wean myself off the T3 supplement. I hope to achieve this in the next few months. My working hypothesis is that the cause of my high rT3 / low T3 was some combination of very low carb dieting, elevated cortisol (perhaps aggravated by stress over my blood lipids!), or malnutrition.

Another possibility is toxins: Dr Davis claims that such chemicals as perchlorate residues from vegetable fertilizers and polyfluorooctanoic acid, the residue of non-stick cookware, may act as inhibitors of the 5′-deiodinase enzyme that converts T4 to T3. Finally, Val Taylor claims that blood sugar over 140 mg/dl causes rT3 dominance. I couldn’t find any studies confirming this claim, and don’t believe it is relevant to my case. Val recommends low carb for diabetics to prevent cholesterol and rT3 issues but warns not to go under 60g carb per day.

Issues with T3 Supplementation

There are some factors to consider before embarking upon T3 supplementation:

  1. Preparation: In order to tolerate T3 supplement you have to be sure that your iron level and your adrenals are strong enough. This requires quite a bit of testing. I’ve read of people who cut corners with unpleasant results.
  2. Practicalities: T3 supplementation requires daily temperature monitoring in order to assess your progress. People who are on the move throughout the day would find this difficult.
  3. Danger: Once you get on the T3 boat you can’t get off abruptly. Your T4 level will drop below range and you will be dependent on T3 until you wean yourself off. If you stopped abruptly you could develop a nasty reaction and even become comatose.

My advice for anyone doing very low carb

As Chris Masterjohn said, in the quote above, if you are going to do very low carb, check your thyroid levels. I would add: Increase the carbs if you find your free T3 falling to the bottom of the range. It might be a good idea to test also for cortisol. A 24-hour saliva test will give you an idea whether your cortisol levels are likely to contribute to an rT3 issue. It might also be a good idea to avoid very low carb if you are suffering from stress – such as lipid anxiety!

Gregory Barton’s Conclusion

I also think my experience may help prove thyroid hormone replacement to be an alternative, and superior, therapy to statins for very high cholesterol. Statins, in the words of Chris Masterjohn,

“… do nothing to ramp up the level of cholesterol-made goodies to promote strength, proper digestion, virility and fertility.  It is the vocation of thyroid hormone, by contrast, to do both.”

Paul’s Conclusion

Thanks, Gregory, for a great story and well-researched ideas. The rapid restoration of normal cholesterol levels with T3 supplementation would seem to prove that low T3 caused the high LDL levels.

However, I would be very reluctant to recommend T3 supplementation as a treatment for high LDL on Paleo.  If the cause of low T3 is eating too few carbs, then supplementing T3 will greatly increase the rate of glucose utilization and aggravate the glucose deficiency.

The proper solution, I think, is simply to eat more carbs, to provide other thyroid-supporting nutrients like selenium and iodine, and allow the body to adjust its T3 levels naturally. The adjustment might be quite rapid.

In Gregory’s case, his increased carb consumption of ~50 g/day was still near our minimum, and he may have been well below the carb+protein minimum of 150 g/day (since few people naturally eat more than about 75 g protein). So I think he might have given additional carbs a try before proceeding to the T3.

Gregory had a few questions for me:

GB: What if one is glucose intolerant and can’t tolerate more than 60 grams per day without hyperglycemia or weight gain?

PJ: I think almost everyone, even diabetics, can find a way to tolerate 60 g/day dietary carbs without hyperglycemia or weight gain, and should.

GB: What if raising carbs doesn’t normalize blood lipids and one finds oneself ‘stuck in rT3 mode’?

PJ: I’m not yet convinced there is such a thing as “stuck in rT3 mode” apart from being “stuck in a diet that provides too few carbs” or “stuck in a chronic infection.” If one finds one’s self stuck while eating a balanced diet, I would look for infectious causes and address those.

Finally, if I may sound like Seth Roberts for a moment, I believe this story shows the value of a new form of science: personal experimentation, exploration of ideas on blogs, and the sharing of experiences online. It takes medical researchers years – often decades – to track down the causes of simple phenomena, such as high LDL on low carb. We’re on pace to figure out the essentials in a year.

Mario Replies: Low Carb Diets and the Thyroid, II

We’ve been looking at papers put forth by Anthony Colpo in support of his idea that low-carb diets can cause “euthyroid sick syndrome” (see his original post on July 1 and a post expanding his case on August 20).  I gave my general perspective on this issue last week: Carbohydrates and the Thyroid, Aug 24, 2011. Briefly, an extreme low-carb diet can create a glucose deficiency, especially if endurance exercise or infection increases glucose requirements, and glucose deficiency invokes the body’s glucose conservation measures, which primarily consist of lower T3 and higher rT3 hormone levels – two hormonal markers of euthyroid sick syndrome. I also offered my view, unchanged from our book, on what level of dietary carbohydrate intake is needed to avoid a glucose deficiency.

Now it’s time to look more closely at the evidence to see if my perspective is consistent with the literature. Our thyroid expert, Mario Renato Iwakura, has been looking into Anthony’s papers to see if they report any negative effects from Perfect Health Diet-level carb intakes. In his first post (Low Carb High Fat Diets and the Thyroid, Aug 18, 2011), he showed that studies cited in Anthony’s July 1 post were generally very high omega-6 diets and therefore did not refute our diet, which prescribes low omega-6 intake. Anthony’s August 20 rebuttal cited a few more experiments which were not high in omega-6, and today Mario is going to look specifically at the issue of carbs. How much carbohydrate intake is needed to avert a glucose deficiency as indicated by decreased T3 and increased rT3?

Mario had assistance from JS Stanton of who reviewed the post pre-publication and contributed some helpful suggestions. Without further ado, here’s Mario! – Paul

After my post on low carb diets and thyroid function, Anthony Colpo wrote a reply that I will address with this post.

First, let me say that neither I nor Paul ever said that:

  1. A high carbohydrate diet has detrimental effects on the thyroid;
  2. Low-carb diets have any “metabolic advantage”; or
  3. A very low carbohydrate diet is healthy or good for the thyroid.

Second, Anthony has been making a case that low-carb diets can produce a condition called “euthyroid sick syndrome,” characterized by low T3 and high rT3. Anthony seems to have supposed that my post was intended to reply or refute his July 1 post. It was not; my post was intended as a treatment of thyroid health generally, and was designed to answer the question of whether the studies Anthony had cited in any way refuted the Perfect Health Diet prescription for thyroid patients.

In the developed world, most cases of hypothyroidism – up to 90% – are diagnosed as Hashimoto’s autoimmune thyroiditis. Hashimoto’s is a complex disease, whose causes are too complex to explore in this post, but in my opinion it is generally caused by exogenous toxins (gluten, mercury, bisphenol-A, bromide, etc) that disrupt gut flora and cause gut permeability and disturbed immunity that allows infections to enter the body and take root in thyroid tissue, after which in susceptible persons an autoimmune attack on the thyroid can develop.

Which infections are associated with Hashimoto’s is still an object of study, but we do know that many of the likely pathogens benefit from high gut, serum, or cellular glucose levels  and therefore we can suspect that a high carbohydrate diet might promote the disease and a low, but not too low, carbohydrate diet, such as PHD, might be therapeutic.

So even if some thyroid-related problems, like euthyroid sick syndrome, may become more likely on a low-carb diet, others, like Hashimoto’s, may be relieved by a low-carb diet. It is therefore necessary to look closely at each condition and at the literature to see which diet optimizes thyroid health – and whether specific thyroid disorders demand different diets.

In looking at the papers cited by Anthony, I’ll borrow his section headings so that readers have an easier time finding the part of his post that I am responding to.

“Here Comes the Boom!”

Anthony, in an attempt to refute my assertation that PUFA may cause thyroid impairment on LCHF diets, cites two papers.

The first was Danforth E Jr et al. [1] This paper reported a number of experiments with multiple low-carb diet variations. In all studies, provided fat was rich in omega-6 fats:

The excess fat in these diets averaged 895 kcal/d consisting of margarine, corn oil, a corn oil colloidal suspension, and fat-enriched soups and cookies. The ratio of saturated to unsaturated fatty acids in these diets was 1:2.5. [1]

However, there was a single experiment which was low in both fat and carb. Anthony wrote:

However, as you scan through the above paper, you will notice that one of the groups followed a zero-carb diet consisting of nothing but lean meat, fish, fowl, and vitamin and mineral supplements. In other words, they ate next to no PUFA.

This particular diet was actually a “protein-supplemented modified fast” consisting of:

a 6-wk period during which the subjects received a protein-supplemented modified fast including 1.2 g/kg ideal weight per d of lean meat, fish, or fowl. This was supplemented by 25 meq/d of potassium bicarbonate and citrate and 200 mg of calcium as carbonate, plus vitamins and iron. [1]

So an 80-kg man would have gotten 100 g lean meat. 100 g chicken breast supplies 165 calories total, 32 calories from fat and 133 from protein. So this “zero-carb diet” provided at most a few hundred calories per day. Anthony’s conclusion:

During this very low PUFA diet, T3 concentrations fell steadily and at six weeks were equivalent to those found after 7 days of fasting (88 ng/dl)!

Here’s the data from the study:

The initial concentration of T3 in these subjects was 155 ng/dl, fell to 87 ng/dl during the 7-d fast, and then rose to 146 ng/dl with refeeding. Initial rT3 concentrations were 25 ng/dl, rose with fasting to 57 ng/dl, and then fell again to 24 ng/dl with refeeding. Slower but similar changes in the concentrations of T3 and rT3 to those of fasting occurred with administration of a protein-supplemented modified fast for 1 wk. During the first week of the diet, T3 concentrations fell from 166 to 109 ng/l and rT3 concentrations rose from 31 to 53 ng/dl. [1]

In short: On a 7-day modified fast providing 130 protein calories per day, the fall in T3 levels is significantly less than on a 7-day true fast.

As the modified fast was continued, T3 concentrations continued to fall and at 6 wk were equivalent to those found after 1 wk of fasting (88 ng/dl). rT3 concentrations, however, returned to their initial values as the fast was continued (39 ng/dl). [1]

So even after 6 weeks, the rT3:T3 ratio was lower on the modified fast (39/88) than after 1 week on the true fast (57/87).

This all looks consistent with Perfect Health Diet arguments that we need at least 200 starch calories and at least 600 carb+protein calories to prevent a glucose deficiency; with Paul’s argument that high rT3 and low T3 is the body’s response to a glucose deficiency; and with the idea that mitigating the glucose deficiency by carb or protein intake will lower the rT3:T3 ratio. It does not speak at all to Perfect Health Diet-style low carb (400 calories from starches, adequate protein) being unhealthy.

Anthony next discusses Bisschop PH et al. [2] He even e-mailed Bisschop to be sure the diet was low in PUFA. But what diet caused a significant decrease in T3 levels? A diet supplying only 2% carbohydrate out of 2483 total calories, or 49.66 calories = 12.41g of carbohydrate. Again, Perfect Health Diet recommends 400 calories (100g) carbohydrate, and argues that, because the amount of glucose that can be manufactured from protein is hormonally limited, even if dietary protein is sufficient at least 200 readily digestible glucose calories should be eaten to avert the risk of a glucose deficiency.

Anthony quoted the following passage from Bisschop PE et al:

Apparently, isocaloric carbohydrate deprivation induces a catabolic state with respect to protein metabolism compared with diets with a normal composition and compared with starvation. This catabolic reaction to carbohydrate deprivation is associated with decreased insulin secretion. Apparently, exogenous carbohydrates and/or insulin induced by exogenous carbohydrates are required for a proper utilization of dietary proteins. [2]

Anthony goes further and says that low carb diets “suck the big one for building muscle”:

So what does explain the reduction in T3 seen on the low-carb diet? Well, remember how I said that Dr. Bisschop and his team also measured urinary nitrogen excretion in the male subjects? Urinary nitrogen excretion is a long-standing and widely employed marker for protein (as in, lean tissue) breakdown. Low-carb diets have repeatedly been shown to increase nitrogen excretion, which is one reason why they suck the big one for building muscle.

The carbohydrate deprivation diet comprised 2% of carbs and 15% of protein. On a 2483 calorie diet, this is only 420 carb+protein calories – insufficient to meet the minimum Paul estimated of 600-800 calories per day to avoid a glucose deficiency. The body simply isn’t being given enough amino acids to meet the body’s glucose requirements. Muscle breakdown necessarily follows.

But, let’s see what happens when you provide more carb+protein. The Volek study [3] provided 8% carbs (184 calories) and 30% protein (704 calories) – still low-carb, but now enough carb and protein to avert a glucose deficiency. Here is Table 2 from Volek et al [3]:

The subjects in the Volek study were asked to maintain their current level of physical activity and to consume adequate dietary energy to maintain body mass. And yet fat mass was significantly (P < .05) decreased (-3.4 kg) and lean body mass significantly increased (+1.1 kg) at week 6.

Lesson: if you don’t want to lose muscle on a VLCD, eat extra protein and at least a bit of carbs!

“Why The Volek Study Proves Absolutely Nothing …”

Anthony wrote:

The study headed by Jeff Volek  is the only one allegedly showing no change in thyroid hormone levels on a low-carb diet, so of course it is eagerly cited by Mario as proof that I’m wrong. Just one wee problem: Volek et al didn’t even measure levels of T3, the critical thyroid hormone in question! Instead, as I explained in my article, the pro-low-carb and Atkins-sponsored Volek team chose to only measure T3 uptake, a test also known as “resin-binding T3 uptake”.

This, of course, is just fine by Mario, who happily extrapolates the results of unrelated studies examining the relationship between thyroid hormones and a bunch of other hormones; studies, I should point out, that did not involve low-carb diets.

The Volek study [3] was cited because it was unique: the only low-carb study that didn’t use a high PUFA diet. As for the failure to measure T3, I agree this was a flaw. However, you cannot reasonably argue that T3 may have decreased with no detectable effect on the human body. You absolutely cannot say that T3 can decrease with no effect on testosterone, IGF-1, glucagon, sex hormone-binding globulin (SHBG), fat mass, or lean body mass. Maybe in an alien body or in another parallel universe … but not in humans.

Anthony next cites Otten MH et al [4]. Study subjects were taken through a succession of diets, eating each diet for only 72h. The two diets that caused the greatest changes in T3 and rT3 were the first two: a diet of 100% fat and another of 50% fat and 50% protein.

Paul has argued that gluconeogenesis is hormonally limited and can generate at most 400 glucose calories per day; this is why zero-carb diets are dangerous. So it is no surprise that these zero-carb diets produce the elevated rT3 – depressed T3 pattern that is the body’s response to a glucose deficiency. Again, this does not argue against Perfect Health Diet-style low carb.

What is interesting about Otten et al is that the diet of 50% carbohydrate and 50% fat showed a decrease of 24% in T3 and an increase of 34% in rT3. It looks like even high-carb diets can induce high rT3 and low T3 if the diet is unbalanced and deficient in protein.

Perhaps the problem is not so much low-carb, but malnourishment in general! High rT3 and low T3 reduce metabolism and may help conserve protein during malnourishment, regardless of whether the threat to protein stores comes from dietary restriction of carbs or protein.

“Fifty Grams I Tell Ya, FIFTY GRAMS!!”

Anthony proceeds to comment on a study, Spaulding SW et al. [5], which was cited by Stabby in the comments. In this study, only fifty grams of carbohydrate on a high fat diet was enough to restore T3 levels to normal:

As anticipated, total fasting resulted in a 53% reduction in serum T3 in association with reciprocal 58% increase in rT3. Subjects receiving the no-carbohydrate hypocaloric diets for two weeks demonstrated a similar 47% decline in serum T3 but there was no significant change in rT3 with time. In contrast, the same subjects receiving isocaloric diets containing at least 50 g of carbohydrate showed no significant changes in either T3 or rT3 concentration. [5]

Anthony’s comment is this:

Mario and Stabby jump on this finding as if it is proof that only fifty grams of carbohydrate is needed to maintain optimal carbohydrate levels. In doing so, they totally ignore the fact that this result was hardly a universal finding. They totally ignore all the other studies showing T3 reductions at higher carbohydrate intakes.

Based on Paul’s view of things, it would be no surprise that this was not a universal finding. Paul estimates that 200 calories of dietary carbs, plus 400 calories from gluconeogenesis, is barely sufficient to prevent a glucose deficiency in a sedentary healthy person. Any perturbation – exercise, infection, protein restriction limiting the availability of substrates for gluconeogenesis – might induce a glucose deficiency.

But it is significant that when circumstances are right, 200 calories per day of carbs can eliminate the T3 drop and rT3 rise that is associated with glucose deficiency. So Spaulding et al is a positive contribution to the debate, and once again it tends to confirm Perfect Health Diet’s analysis.

Anthony cited several other studies in which 200 carb calories was insufficient to prevent a rise in T3. First, Mathieson et al [6]:

Ruth Mathieson and her colleagues from Virginia Polytech and State University placed fourteen obese free-living women on 530-calorie/day diets containing either 44 grams or 94 grams daily of carbohydrate. Both diets caused significant reductions in T3, with the ketogenic diet causing the largest decline.

Recall that Paul believes that 200 carb calories and 600 calories of carb+protein are the bare minimum needed to prevent a glucose deficiency, even when all circumstances are favorable. These diets only had 530 calories total. As carb+protein intake was insufficient to maintain glucose status, it is no surprise that the diets induced a fall in T3.

The other study cited by Anthony was Serog et al [7]. Anthony writes:

Serog et al examined four isocaloric (mean intake 2800 calories/day) diets lasting 1 week each. In two of these, a standard diet containing 45 percent carbohydrate was consumed. The remaining two diets were either low- or high-carbohydrate, and were consumed by all the subjects in random order between the two standard diet phases.

Average carbohydrate intake in grams was 250 grams on the standard diet, 71 grams on the low-carbohydrate diet, and 533 grams on the high-carbohydrate diet. On the standard and high-carbohydrate diets, T3 levels did not change, ranging from 163.3 to 169.5 ng. They declined on the low-carb diet to a mean 148.6 ng. Mirroring these changes, rT3 rose significantly only on the low-carb diet.

What was the fat used? You bet! Soy oil! From Table 1, composition of the Normal Protein Hypocaloric Diet (NHD): protein was provided as casein (14g), skimmed milk (34g), and soy (22g); fats were from soy (16g, 9g linoleic acid); carbohydrates were primarily dairy sugars.

Finally, Anthony cited a study by Davidson and Chopra [8] which found that T3 levels increased as carbohydrate intake increased from 20% toward 80% of energy. Paul himself discussed this study in last week’s post, in response to a cite by Danny Roddy. Paul’s observation was that high T3 levels are harmful to health, and that T3 may be elevated on the 80% carb diet in order to dispose of excess glucose (T3 stimulates glycolysis), so this could indicate a mechanism by which high-carb diets are health impairing. It does not prove that 80% carb diets are healthier than 20% carb diets.


Yes, it is possible to develop a glucose deficiency on low-carb diets. If this occurs, the body will conserve glucose by reducing T3 and increasing rT3.

However, there is as yet no evidence that T3 and rT3 will exit normal ranges when following Perfect Health Diet guidelines.

Until a well-designed study provides contrary evidence, I stand by my assertion that a diet with sufficient but not excess protein, moderate carbohydrate comprising a minority of calories, and high intake of saturated and monounsaturated fat but low intake of polyunsaturated fat is optimal for thyroid function. But this is the Perfect Health Diet!


[1] Danforth E Jr et al. Dietary-induced alterations in thyroid hormone metabolism during overnutrition. J Clin Invest. 1979 Nov;64(5):1336-47.

[2] Bisschop PH, et al. Isocaloric carbohydrate deprivation induces protein catabolism despite a low T3-syndrome in healthy men. Clin Endocrinol (Oxf). 2001 Jan;54(1):75-80.

[3] Volek JS et al. Body composition and hormonal responses to a carbohydrate-restricted diet. Metabolism. 2002 Jul;51(7):864-70.

[4] Otten MH et al. The role of dietary fat in peripheral thyroid hormone metabolism. Metabolism. 1980 Oct;29(10):930-5.

[5] Spaulding SW et al. Effect of caloric restriction and dietary composition of serum T3 and reverse T3 in man. J Clin Endocrinol Metab. 1976 Jan;42(1):197-200.

[6] Mathieson RA, et al. The effect of varying carbohydrate content of a very-low-caloric diet on resting metabolic rate and thyroid hormones. Metabolism, May, 1986; 35 (5): 394-8.

[7] Serog P, et al. Effects of slimming and composition of diets on V02 and thyroid hormones in healthy subjects. Am J Clin Nutr. 1982 Jan;35(1):24-35.

[8] Davidson MB, Chopra IJ. Effect of carbohydrate and noncarbohydrate sources of calories on plasma 3,5,3?-triiodothyronine concentrations in man. J Clin Endocrinol Metab. 1979 Apr;48(4):577-81.

Gary Taubes and Stephan Guyenet: Three Views on Obesity

In a post titled “Ancestral Health Symposium Drama”, Stephan Guyenet begins to expound his scientific differences with Gary Taubes.

Since my views differ a bit from both Stephan and Gary, I thought readers might enjoy a third view.

My General Perspective on Obesity

My view is that obesity is caused in the first place by malnutrition, toxins, and infections. Each can contribute in multiple ways:

  • Malnutrition can affect appetite and energy utilization. Micronutrient deficiencies will increase appetite, regardless of energy balance. Macronutrient deficiencies may also do this. The resulting increased calorie intake may be only partially balanced by increased activity and thermogenesis; fat gain in caloric surplus tends to be more weakly opposed by brain regulatory circuits than muscle loss during caloric deficit. Malnutrition can impair energy utilization by several pathways: for instance, loss of mitochondrial antioxidants may lead to oxidative damage that impairs mitochondrial health. Choline deficiency induces metabolic syndrome and obesity (see Choline Deficiency and Plant Oil Induced Diabetes, Nov 12, 2010). Long-term, malnutrition may induce methylation defects which affect epigenetic regulation of metabolism. These can be passed on from mother to child.
  • Toxins also have multiple pathways by which they induce obesity. For example, diets that combine fructose or alcohol with polyunsaturated fats are very effective at producing metabolic syndrome and obesity in animals, and food opioids affect the endocannibinoid pathways which can be important in obesity and appetite regulation. See Why We Get Fat: Food Toxins (Jan 20, 2011) and Wheat and Obesity: More from the China Study (Sep 4, 2010) for more.
  • Infections have also been linked to obesity. I’ve blogged about how adenovirus infections of adipose cells promote obesity (Obesity: Often An Infectious Disease, Sep 22, 2010), but another very important pathway is from gut infections to obesity. Briefly, gut pathogens release fat-soluble toxins which can enter systemic circulation, and also modulate immune function. Toxins from pathogens have been shown to induce metabolic syndrome in the liver, promoting obesity. Via the immune system, gut flora can promote obesity. I’ve briefly mentioned one pathway (in Thoughts on Obesity Inspired by Stephan, Jun 2, 2011): gut immune modulation in the gut has been shown to determine whether adipose tissue macrophages are in a pro-inflammatory or anti-inflammatory state. A pro-inflammatory state promotes obesity. Research into the many ways gut flora influence obesity is in early stages, but it’s clearly important.

Due to the diversity of factors which conspire to cause obesity, it is a rather heterogeneous disease. Its unifying character is that some combination of causal factors induces “metabolic damage,” such as leptin resistance, in a variety of organs, including the brain. Metabolic damage can affect both appetite regulation and energy homeostasis.

I’ve discussed Stephan’s views and food reward theory (Thoughts on Obesity Inspired by Stephan, Jun 2, 2011). Food reward theory offers a plausible explanation for many aspects of obesity. I agree that food reward is an important factor in obesity, but consider it one among several factors, and believe that different factors may dominate in different people. Also, it seems likely to me that food reward becomes a dominant factor in obesity only after some form of metabolic damage from malnutrition, toxins, or infections begins to affect the brain’s regulatory systems. In a healthy person a highly palatable diet might have little effect on weight for quite some time. Nor am I convinced that low food reward diets are necessarily the best approach for long term weight loss or for the health of the obese, though I do believe they are great for short-term weight loss.

Distinguishing my view from Stephan’s is difficult because the obesity-inducing diets used in animal studies are generally both toxic and malnourishing and highly palatable. The “cafeteria diet” of Cheetos and such – rich in wheat, sugar, and vegetable oil – is an example.

I haven’t previously blogged about Gary’s views, but I consider very low carb dieting to be an imperfect solution for good health generally. (NB: Low-carb, which I endorse, is for me 400-600 carb calories, very low-carb, which I deprecate, is <200 calories.) Ketogenic diets may be beneficial in some cases of obesity, but I believe they should still include some starchy carbohydrates.

The Exchange

Stephan has transcribed the Q&A between Gary and himself and offers revised answers. I’ll insert my thoughts:

GT: How does your food reward hypothesis hypothesis explain a culture in which mothers are obese and their children are starving?  Are the mothers eating Snickers bars and not sharing them with their children?

SG: The food reward/palatability hypothesis of obesity is not mine, it’s a hypothesis that originated in the 1970s, perhaps earlier, and is a major subject of ongoing obesity research.  I don’t expect it to explain every instance of obesity.  Obesity involves multiple factors, an important one of which is food reward and palatability.  That being said, you have to examine a culture’s food habits in some detail, both before and after a change in obesity prevalence, to determine if reward/palatability may have played a role.  I don’t know enough about that specific culture to judge whether food reward would have played a role there.

PJ: Famines occur in impoverished societies with disrupted social institutions. People in these cultures are driven to eat the cheapest calories, which are the toxic grains such as wheat. They also tend to be malnourished, especially during famines. Malnutrition and toxic foods can create the disease of obesity, especially in a suitable infectious disease context.  Once the disease of obesity is induced, periods of caloric availability lead to weight gain which may be defended during subsequent famines. This explains maternal obesity persisting during a period of food scarcity. The slenderness of their children is a result of the disease process not having had enough time to work. It may take decades for malnutrition and food toxicity to induce obesity in the child.

So the element of long-acting causal factors and history eliminates the apparent conflict between an obese mother and a starving slender child.

Because food reward could induce obesity in the mother prior to the famine which is defended later, and food reward may act differently in growing children, food reward theory may be able to explain the situation. But Stephan prudently allows for the possibility that other causes of obesity besides food reward may be at work.

GT: The Pima indians were obese in 1902, following 20-30 years of famine.  How would your theory explain this?

SG: The Pima were first contacted in 1539 by the Spanish, who apparently found them to be lean and healthy.  At the time, they were eating a high-carbohydrate, low-fat diet based on corn, beans, starchy squash, and a modest amount of gathered animal and plant foods from the forest and rivers in the area.  In 1869, the Gila river went dry for the first time, and 1886 was the last year water flowed onto their land, due to upstream river diversion by settlers.  They suffered famine, and were rescued by government rations consisting of white flour, sugar, lard, canned meats, salt and other canned and processed goods.  They subsequently became obese.  Their diet consisted mostly of bread cooked in lard, sweetened beverages and canned goods, and they also suddenly had salt.  I don’t see why that’s incompatible with the food reward hypothesis.  It is, however, difficult to reconcile with the carbohydrate hypothesis.

PJ: The Pima Indian story seems compatible with both Stephan’s and my views, since they ate a nourishing, low-toxicity, low-food reward diet when they were lean but a malnourishing, toxic, high-food reward diet when they became obese. It seems incompatible with Gary’s ideas, since the Pima ate a high-carb diet at all times. Thus it’s a bit surprising Gary is so fond of the Pima story. It weakens, not helps, his case.

GT: There are two possible hypotheses here.  The alternative hypothesis is that sugar and refined carbohydrate consumption changes the regulation of fat tissue, leading to obesity.  The studies you cited in which people lost weight by consuming bland liquid diets would have been low in sugar as well.  “We need an observation that can refute one of the two hypotheses”.

SG: The bland liquid diet in Hashim et al. that caused massive weight loss is called “Nutrament”.  It is 50% carbohydrate, 30% fat and 20% protein.  The primary three sources of carbohydrate in this formulation are lactose (from milk), sucrose (table sugar) and corn syrup.  The bland liquid used in the study by Cabanac et al. (Renutryl), which also caused weight loss, was high in refined glucose and sucrose.  I find this rather difficult to reconcile with the idea that sugar and refined carbohydrate are inherently obesogenic.

PJ:  It’s unclear to me what Gary’s “alternative hypothesis” is. Why are refined carbohydrates different from unrefined carbohydrates? Both may raise blood glucose and insulin levels similarly. If toxic plant foods are the problem, then he should say toxins rather than carbohydrates are the problem. If it’s the macronutrient that’s the problem, why does refining matter?

Stephan scores a point against both Gary and me here, but especially against Gary, since the liquid diets are fairly high in carbs. As there was some sucrose and polyunsaturated fat, this was not a non-toxic diet, and I don’t know if adequately micronutrients were provided – probably not – but on its face the food reward theory seems to work best in explaining this experiment.

GT: “How was it bland then?”

SG: The diet was a liquid formulation that (judging by the ingredients) probably tastes like powdered milk.  The subjects were drinking that for 100% of their calories.  That fits any reasonable definition of a low reward/palatability diet, regardless of the sugar.

GT: What about the Mexican-Americans in Star county, Texas, who were obese despite the fact that there was only one restaurant in the whole town?

SG: Again, you have to examine a culture’s food habits in some detail, both before and after a change in obesity prevalence, to determine if reward/palatability may have played a role.  I don’t know enough about that specific culture to judge whether food reward would have played a role there.

GT: How can we differentiate between altered palatability and altered carbohydrate intake as important factors in the rising obesity prevalence of industrializing nations?

SG: Increased carbohydrate intake is a particularly poor explanation for obesity in industrializing populations, as the majority of them (for example, most of Asia and Africa) are going from a diet very high in carbohydrate, to one that is lower in carbohydrate and higher in fat.  There are also a smaller number of cultures that developed obesity as they went from high-fat to higher carbohydrate, industrialized food.  Therefore, the ideas that carbohydrate or fat are inherently fattening don’t appear consistent with the evidence as a whole.  An alternative explanation whereby both fat and carbohydrate, as well as other factors, are important for reward/palatability, an excess of which contributes to obesity, fits the evidence better.

PJ: It seems to be easiest to induce obesity with a roughly equal mix of carbs and fat; both low-carb and low-fat diets tend to be less obesogenic. This result is compatible with Stephan’s views because carb and fat together are more rewarding than either alone, and with my views because carb-fat combinations can be highly toxic – for instance, a fructose-PUFA combination is more toxic than either alone; or carbs feed gut pathogens while fats carry their toxins into the body.

It is unclear how Gary would explain the evidence from both animal studies and human populations that obesity becomes more likely as high-carb diets shift toward more fat.

Of Glass Houses

Stephan is a model of scholarly virtue, so Gary’s challenge at the end of his talk was a shock. I thought Stephan’s original reply – “Thank you for the advice” – was perfect, but Stephan revises it:

GT: “I would just recommend in the future you should pay attention to populations that might refute your hypothesis rather than just presenting populations that support.  That’s always key in science.”

SG: People who live in glass houses shouldn’t throw stones.

Presumably Stephan is challenging Gary to address some of the populations who seem to refute his hypothesis: Asian populations that have become more obese while dropping carbs from 75% to 50% of diet, or the Pima who remained lean on a high-carb diet for centuries.

In other words, to seek a theory that can explain all phenomena, as a scientist should.

In general, I find Gary’s work rhetorically artful but not very helpful to scientific progress. He often neglects to consider the full implications of his own evidence. This is especially true when he ventures into molecular and cellular biology.

For instance, he uses genetic lipodystrophies to illustrate that fat storage can be a disease of molecular biology, rather than excess food consumption. Now, the mutations in these lipodystrophies are generally not in insulin, the insulin receptor, or even centrally located on insulin pathways. So the lipodystrophies show that other molecules besides insulin can be responsible for fat storage (or negative regulation of fat storage), and may be relevant to obesity.

But when he looks into which molecules might be responsible for obesity, he offers only one candidate: insulin.

More startling is his neglect of perhaps the single most important molecule in obesity, leptin. Stephan writes:

[H]e sent me a manuscript for his book Why We Get Fat and asked for my advice prior to its publication.  I explained to him that he needed to use the word “leptin” in the book, particularly when discussing animal models of obesity that are obese because of defects in leptin signaling (ob/ob mice and Zucker rats, for example).

This is just like his use of lipodystrophies: mice get obese due to mutations in leptin, but he doesn’t discuss the role of leptin, preferring to keep the spotlight on insulin.

I don’t want to sound harsh because I think Gary is on the side of the angels. He has done very beneficial work refuting saturated-fat-phobia and encouraging low-carb diets, which improve the health of nearly all westerners who adopt them (although the reason is probably reduced toxicity from wheat and sugar, rather than reduced carbohydrate calories).

But I think he would do well to be more generous to others. I was excited when he began blogging, but disappointed by his first post:

conventional wisdom … almost incomprehensibly naïve and wrong-headed … nonsensical notion … I’ve been consistently amazed at the ability of researchers … to accept some of the rote ideas … without seemingly giving it any conscious thought whatsoever, or without wanting to ask the kinds of questions that a reasonably smart junior high school student should ask if given the opportunity…. I don’t understand this failure of intellect … nonsensical explanations … he falls short, as he’s working outside his area of expertise … we’re being fed nonsense … we will typically pass that nonsense along … If the experts had ever been open to a little skeptical thinking from others or had they been appropriately skeptical themselves … What’s been needed (and still is) was for someone (a reasonably smart 14-year-old would suffice) to ask the obvious questions and then insist on intelligent answers.

I find such talk ungenerous; and ironic, because in places in that very post Gary’s own reasoning is unsound.

Biology is complex, none of us have all the answers, and a lifetime is too short to acquire all the answers. Since we have no choice but to live in glass houses, we should all be humble, and refrain from casting stones.

Low Carb Paleo, and LDL is Soaring – Help!

To Kindy, Zach’s parents, and the NBIA/PKAN kids: I’ve been reading papers on the disease and trying to figure out the best diet for the disease. But the biochemistry is a bit complex, more complex than I realized last week, and I want to make sure my advice is sound. So I’m delaying my NBIA/PKAN/ketogenic diet posts until next week.

My sincere apologies for the delay!

I’m a little busy this week – busy with work, busy with learning about NBIA/PKAN, and eager to spend time with my brother who is visiting from Germany – and so I thought I’d do a “You be the doctor” quiz.

Here’s the puzzle. Someone adopts a low-carb Paleo diet. Very healthy diet, right? But their LDL cholesterol level starts to rise. And rise. And rise.

Larry Eshelman emailed me last December with this problem. His LDL history:

  • 103 mg/dl (1990-2002, eating a low fat diet)
  • 115 mg/dl (2002-2007, eating a low carb diet)
  • 195 mg/dl (2007-2009, after reading Gary Taubes and adding saturated fat)
  • 254 mg/dl (Dec 2009, very low-carb Paleo for 5 weeks)
  • 295 mg/dl (Jun 2010, very low-carb Paleo for 7 months)

(SI system readers, convert to mmol/l by dividing by 38.67.)

A common problem

This is not a terribly uncommon problem in the Paleo community; it afflicts famous and brilliant bloggers as well as ordinary folks. It’s been discussed by Richard Nikoley in several posts:

Some examples of high LDL on a Paleo diet, with links – most of these provided to me by Larry (thanks Larry!):

OK, that’s enough: this is a minority phenomenon, but it’s definitely not an exceptional n=1 phenomenon.

Larry’s Progress

Larry wrote me at the beginning of December asking for advice. He implemented everything I suggested. I just heard back from him this week with new data.

His LDL decreased from 295 mg/dl to 213 mg/dl in a recent test. His HDL rose from 74 mg/dl to 92 mg/dl. His triglycerides fell from 102 to 76 mg/dl.

LDL is still high, but improving; the others are excellent and improving.

So, quiz questions:

  • Can you guess what my December advice to Larry was?
  • What causes these cases of soaring LDL on Paleo? (Of course, there are multiple possible causes of high LDL, but I think among Paleo dieters one explanation is more likely than others, and that’s what I’m looking for.)

My answers tomorrow night.

UPDATE: Answers here: Answer Day: What Causes High LDL on Low-Carb Paleo?