Carbohydrates and the Thyroid

Mario’s post last Thursday (Low Carb High Fat Diets and the Thyroid, Aug 18, 2011), looking at a series of studies cited in a July 1 post by Anthony Colpo, elicited a reply from Anthony.

The exchange turned out to be a blessing, because it is generating some insights on topics of fundamental importance.

Low-Carb Dangers

A motivating factor for our book was Paul’s bad experience with very low carb dieting. We felt obliged to warn the Paleo community that it was possible to become deficient in glucose and that this could be dangerous. We’ve blogged about “Zero Carb Dangers” (see especially Dangers of Zero-Carb Diets, II: Mucus Deficiency and Gastrointestinal Cancers; Danger of Zero-Carb Diets III: Scurvy; Dangers of Zero-Carb Diets, IV: Kidney Stones). Our work has persuaded many in the Paleo and low-carb communities to eat more “safe starches” including white rice. We recommend a carb intake that approaches the body’s total glucose utilization.

We do recommend ketogenic diets and low-carb diets as therapies for many neurological disorders and some infections, but believe that even ketogenic diets should generally include at least 200 glucose calories per day.

So when we consider claims that low-carb diets can be dangerous, it’s not without sympathy.

At the same time, given the therapeutic potential of low-carb and ketogenic dieting, and the likelihood that humans are evolutionarily adapted to a range of macronutrient intakes, we don’t think it’s appropriate to repudiate low-carb entirely.

This places an onus on us to closely examine the evidence, understand precisely when a low-carb diet passes from healthy to unhealthy, and make clear recommendations for how much dietary glucose is needed in different circumstances to avoid negative consequences.

The Issue of Low-Carb and the Thyroid

One problem that sometimes occurs on low-carb diets is a syndrome called “euthyroid sick syndrome,” characterized by low T3 and high reverse T3 hormone levels and elevated cortisol.

Here’s our friend and gracious podcast host, Danny Roddy:

[A low-carb] diet will lead to an elevation of catabolic stress hormones, while [a high-carb diet] has been shown to increase thyroid hormone triiodothyronine (T3), increase testosterone, and decrease cortisol, the anti-hair, pro-misery stress hormone (here, here, here (PDF), & here).

And here’s Anthony Colpo in his July 1 post:

[D]ecreasing carbohydrate intake to low levels results in diminished levels of T3 and/or increased rT3, something most aspiring fat-burners wish to avoid desperately.

Few things are more essential to good health than proper thyroid function. So this is clearly an issue we have to investigate and understand. It could impact our prescription for the minimum level of carb intake needed for good health.

Why Mario’s Post Emphasized Omega-6 Fats

Anthony seemed to think that Mario’s emphasis on the dangers of high-omega-6 diets was intended as a denial that low-carb specifically could be the cause of thyroid trouble. No.

The studies in question compared low-carb high-fat diets with other diets. In some but not all studies, thyroid function was impaired on the low-carb high-fat diet.

In looking at the studies cited by Anthony plus a few others, Mario found that thyroid function was impaired on all of the low-carb high-omega-6 diets but none of the (admittedly few) low-carb high-saturated-fat diets.

This led him to emphasize the role of the fatty acid type, rather than the amount of carbohydrates. It is also supportive of Perfect Health Diet claims that high omega-6 is toxic whereas high saturated fat is not.

Mario did not have space to treat the dangers of glucose deficiency for the thyroid, especially since the studies he was examining did not provide compelling evidence about the effects of dietary carbohydrate restriction (once the possibility of PUFA toxicity was accounted for). So he didn’t venture into this question, other than to assert the importance of “moderate” carb consumption.

But now we will – in the remainder of this post, and two upcoming guest posts.

Let’s explore the circumstances under which we might expect low-carb diets to cause “euthyroid sick syndrome.”

The Limits to Glucose Production

Let me begin by revisiting the initial post in our Zero-Carb Dangers series (Dangers of Zero-Carb Diets, I: Can There Be a Carbohydrate Deficiency?, Nov 10, 2010). I’ve been meaning to correct that post for some time, and this seems a good occasion.

That post emphasized size of the liver as a limit on its ability to synthesize glucose from protein. There is, indeed, a physical limit to the liver’s ability to manufacture glucose from protein. As long as unlimited fat is available for energy production and unlimited protein is available as a gluconeogenic substrate, the limit is determined by the oxygen supply to the liver and is about 400 g / 1600 calories per day.

However, this theoretical limit is never reached in healthy humans, except in some diabetics (as Nigel Kinbrum pointed out). The liver’s conversion of protein to glucose is controlled hormonally; insulin and glucagon are the most important players, with insulin inhibiting gluconeogenesis and glucagon promoting it.

Diabetics can have very high rates of gluconeogenesis because their pancreatic beta cells may no longer produce insulin even as their pancreatic alpha cells continue to produce glucagon.

In normal healthy humans, basal hormone levels are balanced so that during fasting or starvation, the liver and kidneys manufacture minimal but sufficient glucose while sparing protein as much as possible.

In a normal person, the liver and kidneys together never produce more than about 100 g / 400 calories glucose per day from protein. In the absence of hormonal dysregulation, this is a fairly hard limit.

Glucose Utilization and Glucose Deficiency

We discussed this in the book, and I won’t repeat the evidence. Suffice it to say that everyone consumes at least 600 glucose calories per day, a majority by the brain but also extensive amounts for structural components of the body – glycosylated proteins which coat every cell, and glycoproteins which are major components of mucus, joint lubricants, and connective tissue – and for immune function (since glucose is needed to produce the reactive oxygen species that kill pathogens).

Because limited research has been done on this subject, it’s possible that we’ve underestimated the body’s glucose needs. It could be as high as 800 glucose calories per day. It’s not likely to be lower.

This is for sedentary healthy people. Two factors may substantially increase glucose utilization:

  • Infection. Many pathogens consume glucose – indeed, people with parasitic infections can sometimes have great difficulty obtaining enough glucose from food – and the immune system also consumes glucose.
  • Athletic activity. Exercise can consume large amounts of glucose.

Let’s look at athletic activity. The Mayo Clinic lists the amount of calories burned per hour of exercise of various kinds, and the most intense types of exercise, such as running or cycling at race speeds (>20 mph), may burn 1,200 calories per hour. Most of these calories come from fat, but 30-40% may come from glycogen, and glucose is consumed to replace the glycogen. Thus, a runner or cyclist may burn up to 400 glucose calories per hour of training.

In a cyclist, runner, or swimmer who trains 2 hours per day, therefore, glucose needs may be quite a bit higher than in our sedentary healthy person. Such an athlete may be consuming ~1500 glucose calories per day.

Yet at most 400 calories of glucose per day can be manufactured from protein. It’s clear that athletes need to eat a fair amount of carbohydrate to avoid a glucose deficiency.

Anthony Colpo is a cyclist and athlete who routinely engages in intense endurance exercise. His unusually high glucose utilization is presumably what made him vulnerable to glucose deficiency syndromes – and therefore more sensitive than others to the dangers of low-carb diets.

The Basis for Our Carbohydrate Consumption Recommendations

Let’s go back to our sedentary healthy person, and let’s consider the minimum dietary glucose that person needs to avoid difficulty.

First let’s consider a person who eats a large amount of protein – 600 calories per day, about double the intake of an average American.

Roughly 200 calories per day may be needed for structural uses, leaving 400 calories per day for possible conversion to glucose.

But if protein consumption is lower, there may not be enough substrate to create 400 glucose calories per day. This may lead to hormonal changes that try to conserve protein by limiting gluconeogenesis.

Now let’s look on the glucose side. If 600-800 glucose calories are utilized by the body daily, and at most 400 of those can be manufactured from protein and at most ~300 can be displaced by ketones, then someone on a zero-carb diet is living right on the margin of glucose deficiency.

And this is before athletic activity or infections are considered.

If 200 glucose calories per day are consumed, and if 400 protein calories are consumed, and if MCT oil (a ketogenic substrate) is consumed to make it easier to generate ketones to displace glucose, then one might just barely meet the body’s structural glucose and protein needs on a ketogenic diet. This is why we recommend that ketogenic diets include at least 200 calories from starch.

But it’s not really desirable to live on the margin of glucose deficiency, especially if you’re not making it easy for your body to generate ketones. For this reason, our normal diet recommends 400 calories or more from starches.

The Trouble with Vegetables

We generally advise not counting vegetables as carb calorie sources. This often puzzles diabetics who note that vegetables have some sugar – typically, about 80 calories per pound – and that consuming vegetables raises their blood sugar levels.

The reason we recommend not counting vegetable calories is that digestion of vegetable matter is an energy-intensive process that consumes glucose. Gut cells consume glucose directly, and also vegetables have a lot of fiber which causes gut bacterial activity which in turn leads to immune activity which consumes glucose. This glucose consumption by the gut and immune system occurs over an extended period of time after vegetables are eaten – perhaps 6 hours. But vegetable sugars are digested quickly – mainly in the first hour. So you can have a surge of blood sugar due to vegetable sugars, even if the vegetables make no net contribution to daily glucose balance.

So it’s really starches and fruits that are the useful sources for meeting the body’s carb needs.

What Happens When There is a Glucose Deficiency?

When the body is deficient in glucose, the hormonal milieu changes to help maintain body functions while conserving glucose and protein.

Two of the important hormones are cortisol and T3.

T3, the most active thyroid hormone, has a strong effect on glucose utilization. T3 stimulates glucose transport into cells, and transport is the limiting factor in glucose utilization in many cell types. In hyperthyroidism, a condition of too much T3, there are very high levels of glucose utilization. Administration of T3 causes elevated rates of glycolysis regardless of insulin levels.

The body can reduce T3 levels by converting T4 into an inactive form called reverse T3 (rT3) rather than active T3. High rT3 levels with low T3 levels lead to reduced glucose transport into cells and reduced glucose utilization throughout the body.

Cortisol is a hormone that helps prevent hypoglycemia, a condition of low blood glucose. It reduces glucose utilization and increases gluconeogenesis.

So the syndrome of low T3, high rT3, and high cortisol can be understood as a diagnostic pattern of a systemic glucose deficiency.

What Is “Euthyroid Sick Syndrome”?

Euthyroid sick syndrome is defined as “a state … where the levels of T3 and/or T4 are at unusual levels, but the thyroid gland does not appear to be dysfunctional.” Specifically, “Reverse T3 are generally increased signifying inhibition of normal Type 1 enzyme or reduced clearance of reverse T3. Generally the levels of Free T3 will be lowered.”

Wikipedia’s list of causes includes:

  • Fasting, starvation (PAJ: These induce glucose deficiencies, especially if there is insufficient protein available to sustain even the normal 400 calories/day glucose synthesis.)
  • Sepsis (PAJ: Infection increases glucose requirements.)
  • Trauma (PAJ: Fabrication of structural glycoproteins and protein glycosylation is increased during wound repair.)
  • Malignancy (PAJ:  Cancers consume large amounts of glucose.)
  • Hypothermia (PAJ:  Shivering, like endurance exercise, consumes glycogen.)
  • Cirrhosis (PAJ: Damage to the liver may reduce its ability to synthesize glucose, forcing glucose conservation.)
  • Chronic renal failure (PAJ: The kidney is the other organ besides the liver that synthesizes glucose from protein. So kidney damage will reduce the body’s ability to synthesize glucose.)

Looking at this list, it seems that euthyroid sick syndrome may be just another name for a systemic glucose deficiency.

If glucose deficiency is the cause, then obviously low carb diets are going to be a risk factor for euthyroid sick syndrome.

This is not to say that low carb diets will automatically lead to euthyroid sick syndrome. A sedentary person free of infections may be quite normal and healthy on a very low carb diet. This is why most low carbers do not experience the condition.

But if other risk factors, like infection, cancer, or endurance exercise, are present, then the odds of developing euthyroid sick syndrome on a low carb diet may become quite high.

Diagnostic Value of rT3:T3 Ratio for Low-Carb Dieters

Here’s an interesting implication of today’s analysis.

The ratio of rT3 to T3 may have diagnostic value for glucose status and therefore for the presence of infections or cancers. It might not be a bad idea for low-carb dieters to monitor these hormone levels, and to eat enough “safe starches” to keep their rT3:T3 ratio at normal levels.

The rT3:T3 ratio is likely to be of much greater clinical value to low-carbers than to the average high-carb American. So even though doctors rarely test for it, low-carb dieters may find it quite useful.

Are High-Carb Diets Without Risk?

In the wake of Anthony’s reply I was amused by a Twitter conversation between @DannyRoddy and @StabbyRaccoon – two of the smartest and nicest people on the Web.

As noted above, Danny believes that high-carb diets might be beneficial by creating above-normal T3 levels:

I believe the real question is: what range radically increases T3?…

I’m more concerned where CHO starts dramatically increasing T3.

Stabby paid me the honor of valuing my opinion:

maybe Paul … could look into it.

Alright, let’s look (briefly) into it.

In the quote from Danny on potential risks of low-carb diets, he cited several papers. One of them was this:

To evaluate the effect of changes in dietary carbohydrate (CHO) and excessive caloric consumption on circulating thyroid hormone levels, six normal weight subjects were fed five separate diets: three isocaloric diets with 20%, 40%, or 80% CHO and two hypercaloric (+2000 calories) diets with 20% or 40% CHO for 5 days each as outpatients. T4, T3, and rT3 concentrations were measured in plasma samples collected on the morning of the sixth day. At least 1 week of the subjects’ usual diets intervened between each experimental diet.

Mean T4 and rT3 levels were similar after all diets. Pair-wise comparisons among all five diets revealed significantly (P < 0.005) increased T3 concentrations after both hypercaloric diets compared to the iso-20 and iso-40 diets, and after the iso-80 compared to the iso-20 diet. A multiple regression analysis of the data revealed the highest correlation of T3 levels with total calories (r = 0.68; P < 0.001) rather than with the intake of CHO (r = 0.46; P < 0.025), fat (r = 0.49; P < 0.02), or protein (r = 0.30; P = NS).

I haven’t read the full study yet and find this abstract mildly puzzling. On the one hand, the multiple regression analysis shows that fat, not carbohydrate, is the most effective macronutrient at raising T3. Maybe Danny should eat a high-fat diet to raise his T3.

On the other hand, the normo-caloric 80% carb diet had more T3 than the normo-caloric 20% carb diet. So maybe carbs do increase T3 more than fat.

Now, hypercaloric (positive energy balance) diets are associated with a variety of diseases including obesity and metabolic syndrome. Stephan Guyenet has argued that positive energy balance is itself inflammatory and damaging, and that high-reward foods which induce overeating may directly cause metabolic diseases.

In this study, T3 concentrations were increased similarly on both hypercaloric (2000 excess calories) 20% and 40% carb diets and normo-caloric 80% carb diets. Could it be that some of the ill effects of hypercaloric diets will also be present on normo-caloric high-carb diets?

Of course, with any hormone we have to ask what the right amount is. Usually both too much and too little are problematic. This is certainly true of thyroid hormones.

High T3 concentrations are characteristic of the disease hyperthyroidism and have negative effects. One of the effects of high T3 levels is enhanced transport of glucose into cells. For instance:

Pre-treatment of these cells with T3 moreover substantially enhances the stimulatory effect of insulin such that at maximally effective hormone concentrations the effects of T3 and insulin on glucose transport are more than additive and indeed nearly multiplicative …

The extra glucose transported into cells is disposed of through glycolysis. Glycolysis is the characteristic metabolism of cancer cells, so high T3 might promote the cancer phenotype.

Indeed, hyperthyroidism increases the risk of ovarian cancer by 80%.

Glycolysis also occurs in the cytosol, making glucose and downstream energy substrates like pyruvate and lactate available to bacteria. Thus, high T3 may promote bacterial infections.

Indeed, thyroid storms can cause sepsis.

Those who have been following CarbSane’s exposition of the dangers of lipotoxicity may be interested to find that high T3 not only increases circulating glucose levels and rates of glycolysis, but also circulating free fatty acid levels:

Hyperthyroidism, which was induced by administration of tri-iodothyronine (T3) to rats for 2, 5 or 10 days, increased fasting plasma concentrations of glucose, insulin and free fatty acids. Administration of T3 for 2 or 5 days increased the rates of glycolysis at all insulin concentrations studied …

Elevated free fatty acids seem to be the primary cause of diabetes.  Here elevated free fatty acids are associated with high glucose and with a hormonal trait – high T3 – associated with high-carb diets.

(Aside: This kind of evidence is why we have to be a bit cautious in assuming that free fatty acid levels, and thus diabetes risk, are higher on low-carb high-fat diets. Recently CarbSane and I had a brief discussion on this topic: see this post on her blog and the comment thread. She leans toward the idea that more dietary fat = more free fatty acids and thus more lipotoxicity; to me the issue is far from clear, as the need to dispose of glucose will tend to inhibit drawdown of free fatty acids. I think that moderate carb consumption, near the body’s glucose utilization, rather than high carb consumption may minimize lipotoxicity. However, concerns over lipotoxicity might lead us to revisit our suggestion of ketogenic diets for diabetes.)

Getting back to the question Stabby asked me to look into: I have only a provisional response. I have given only the most superficial of looks at the literature. I am mainly tossing out topics for further investigation (hopefully by others!).

But at a glance, I don’t see any obvious reasons to change the judgment of our book that moderate carb consumption, close to the body’s glucose utilization needs, is optimal. In my judgment, “dramatically increasing T3” by eating a high carbohydrate diet (if, indeed, a high-carb diet does this) is probably undesirable. Rather, it’s best to eat a moderate amount of carbohydrate that keeps T3 at physiologically normal, healthy levels. Both too much and too little T3 – and, perhaps, too much and too little dietary carbohydrate – may be dangerous.


In regard to Anthony Colpo, I’d like to extend an olive branch, and reiterate the following points:

  • The purpose of Mario’s post last Thursday was not to show that Anthony was right or wrong, but to find out whether we were right or wrong.
  • Although we are more sympathetic than Anthony to low-carb diets, we agree that they have risks. Yes, it is possible to become glucose deficient.
  • I stand by Mario’s post. I don’t believe there are any errors in it.
  • Nothing Mario said contradicted the main points of Anthony’s July 1 post to which it linked. Mario (and we) endorsed “moderate” carb consumption, not very low carb diets, and Mario’s focus on the dangers of high-omega-6 diets should not be construed as a denial of the dangers of very low-carb diets.

Anthony and I exchanged increasingly cordial emails over the weekend, are sending each other copies of our books, and I hope we will be on good terms even if our diet ideas and study interpretations are not identical.

In regard to rT3:T3 ratio, it might be interesting to compile some data on rT3:T3 ratios and carb intake among low-carbers. It may be that studying how rT3:T3 ratio varies with carb consumption will give us a clearer idea of optimal carbohydrate intake. I would expect there would be some “plateau region” of carb intake over which rT3 is low and T3 levels are stable. At very high carb intakes, T3 might be elevated in order to promote glucose disposal; at very low carb intakes, the euthyroid sick syndrome of elevated rT3 and depressed T3 might hold.

Finally, a look at upcoming posts. Yes, long as this post was, we’re not done exploring these issues.

Anthony cited some more papers in his reply to Mario, and Mario will respond in detail: what do those studies prove? The purpose of this is to evaluate our diet to see if our advice is sound, not to feature any disagreements Mario may have with Anthony, or to prove anyone wrong.

In the post after that, we’ll have a fascinating personal story from Gregory Barton. Gregory’s experience connects euthyroid sick syndrome to the vexing issue of high LDL on Paleo diets, and as such ties in with some points Chris Masterjohn has made on the role of thyroid hormone in LDL pathways. As such it may help us reach some closure on two of the outstanding problems that have troubled the low-carb Paleo community.

And if we’re not tired of the issue after those posts, commenter Valtsu has been sending me references to papers discussing links between infections and euthyroid sick syndrome. It looks like toxins and inflammatory cytokines released during infections can disrupt the ability of the hypothalamus to regulate thyroid hormone levels. This could have implications for other diseases besides euthyroid sick syndrome – including obesity, which often features disruption of the hypothalamus’s regulation of energy utilization.

So I think this little controversy is leading us to some productive discoveries. Therefore, I’d like to thank Anthony for raising the issues in the first place. Out of disagreement may come insight.

Leave a comment ?


  1. Hi Jeff,

    I wouldn’t advise going very high carb but certainly I think you should eat at least 600 carb calories a day. That’s equivalent to about a pound of cooked white rice or a pound a half of white potatoes.

  2. A big thanks to everyone’s posts and to Paul in particular. I have been VLC for over 18 months now but have struggled with sugar cravings (which often lead to binges when particularly stressed), loss of menstrual cycle nearly 12 months ago and bleeding gums, so can relate to many other posts. Have tried Primal/Whole 30/Primal Body Primal Mind etc and none have worked for me. After reading PHD (a few times to get my head around it all!), I will be giving this a go exclusively (not trying to mix and match theories), but would like to try the weight loss version as have put weight on after being VLC and not feeling comfortable in my own skin as a result. Thanks again everyone – Paul’s posts are invaluable, but so are everyone’s comments. A special note to Jaybird – although I don’t have a lot of weight to lose, you are a particular inspiration and so will be giving your weight loss method a go as outlined in your post and the comments from your post.

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  5. Vicki Jacob-Aas

    I read a lot of messages stating ‘may be dangerous’ as here but never statements like LCHF actually causes serious problems. I do read that high carbs causes serious problems.
    Where is your proof that LCHF, Atikns or any of these diets genuinely cause health problems? Show me those, and I’ll consider your arguments.
    Right now, all I see is LCHF helping obese people lose weight and deal with their serious health issues.

    • Hi Vicki,

      Our diet is low-carb and high-fat. Typically 20-30% carb 50-65% fat.

      For the dangers of going too low-carb, see our series on “Zero-Carb Dangers”.

      Best, Paul

      • Vicki Jacob-Aas

        Ok – fair point! Sorry; should have read more closely – I think I am just a bit defensive, constantly reading negative things about LCHF diets.

  6. Paul,
    What are your thoughts on “anemia being a deal buster”?
    It was mentioned on Kresser’s podcast (episode 3, 21:20 min.,), but not really explaining why that is. Kresser said its because anemia is such a complicated topic. What are your thoughts?
    Along with Kresser, would the first lab markers you look for (w someone w HT symptoms, including anemia) are oxygen deliverability and blood sugar values (Hemoglobin A1C tests, I’m guessing)?
    (Dr. K on Underground Wellness, 52 min)

    • Hi Henry,

      I’m not all that familiar with anemia. I know it has many different causes, many of which can be distinguished by testing different markers of iron status, so the first step is always to go to the doctor and get it investigated.

      I would leave that one to doctors, or a knowledgeable practitioner like Chris.

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  8. T3/rT3 Ratio:

    Sounds like something to track… but what should the levels be? I see on various blogs that you want the ratio to be under 20, but I cant seem to find any reference ranges or any literature about this. Does anyone have any evidence-based recommendations?

    After seeing my LDL skyrocket (TC 400, LDL 300), I found these posts and started adding back some carbs. I probably ate about 100g/day starch for about 2 weeks before pulling a thyroid panel. Prior to this I was prob 75g/day carbs but entirely in vegetable matter, so I’m not sure if that should count as glucose or food for bacteria to produce short chain FA.

    In any event, I retested TC (after 2 weeks of 100g/d starchy carb consumption),and it went down from 400 to 340; with a corresponding drop in LDL-C.

    I also got a full thyroid panels; and they were all within “reference range”, so of course my doc completely ignores the data. TSH 2.09; FT4 1.27; FT3 2.9; rT3 20. If I’m doing the math correctly, my rT3/FT3 ratio = 14.5.

    Anyway, here is a data point to add to the “low carb FT3/rT3 ratio database”. I don’t know if the low ratio (but is it really low?)is due to the VLC diet I was on for a year, or if it in fact improved from the 2 weeks of adding back carb. In a few weeks I will retest and repost a new ratio based on a longer period of increased carb intake.

    • Ed, according to the people at Stop The Thyroid Madness, the ration of FT3:RT3 should be 20 or greater, not less than 20. Also, to calculate the ration you typically need to change the units. (Maybe you did that already, just wanted to point it out in case you hadn’t). I hope things are improving for you, I also have an RT3 imbalance with very low body temperatures.

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  10. This information has been extremely helpful to me, thank you so much for compiling it. Although we decided to switch from the GAPS Diet to your Perfect Health Diet primarily because my husband’s energy levels were declining (he has paroxysmal nocturnal hemoglobinuria — any plans to blog about acquired genetic mutations?) I hope to improve, also. I have an RT3 imbalance. Supplementing with iodine and selenium has given me my energy back, which has been WONDERFUL. I’m still waiting for my body temperature to get into the normal range . . .

  11. thankfully stopthethyroidmadness has now made it easy to calculate the RT3 ratio. The calculator allows you to choose the units that match your particular lab results.
    (no need to do any painful unit conversion yourself anymore & risk errors).
    here’s the link;

  12. Superb post Paul, thanks. Two questions:

    1) You’re saying there’s a physical limit on the liver’s capability to produce glucose from protein. What’s your personal view on how much glucose the body can produce from glycerol? I found this study interesting:

    2) How does your answer to question 1) relate to the body’s capability of glucose production? Are you saying that the maximum amount of glucose the body can produce is 400g and that if a larger % of that number come from glycerol that just means less protein is being used?

    Thanks a lot and regards from Norway!

    • Hi Bjarte,

      As the study says, glycerol conversion to glucose is going to be limited by the supply of glycerol. Since free fatty acids are toxic, there won’t be any extra lipolysis to generate glycerol; lipolysis will arrange to generate just the amount of free fatty acids the body needs. Glycerol has about 12% of the calories in triglycerides and phospholipids. So even if you get 85% of energy from fat, you can get at most 10% of energy from glycerol released from fat.

      So, to get adequate glucose from fat you’d have to eat an extremely hypercaloric diet.

      But yes, that glycerol would substitute for protein.

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  14. Are your recommendations universal? Will it hold true for an active man who’s 6’5″ VS a small girl who’s 5’2″?

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  17. Hello,

    I have been on low carb high protein for a few months and have started having thyroid symptoms. I am also an active athlete and long distance runner. After coming across this blog, i rentroduced white rice.

    However, I am concerned in finding out if any T3 damage can be permanent or is it reversible?

  18. Any starch or refined sugar I eat gives me abdominal discomfort which I assume is from SIBO.

    I eat 1 portion of enzyme assisted fruit, grapes or cooked apples daily to prevent ketosis but otherwise I am on low carb diet.

    I am worried about my thyroid but I really don’t know how to up my carb intake to those levels without getting really sick.

    I am trying raw garlic right now, it seems to be helping but while my condition still exists I can’t eat carbs.

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  20. Great post..visit our site for good tertments for Back Pain, Diabetes, Fibromyalgia, Thyroid, chronic pain, sciatica, whiplash, headaches & nutritional disorders.

  21. This is all so interesting. I am an ovarian cancer survivor, twice now, ’99 and 2010. Nearly died this last time, but have surprised my docs by surviving and remaining in remission. I was on the blood Type diet for Type O for 8 years after my first bout, and it served me well. I became sick again when I went off of it. This time, I went back on it, and then went further to the paleo diet. I have been on that for a little more than a year and a half. Although I stopped gaining weight on it, I have not lost any (could stand to lose about 15-25 pounds). I am sure it is related to my thyroid (which tests “normal”). (No eyebrows on the outside). Since reading much of your book, I have increased my carbs to about 100 to 120grams a day (which, on a 1400 Calorie diet, is plenty). We will see if it helps. I’m also eating two sheets of Nori each day for some iodine. This sentence caught my eye: ” It looks like toxins and inflammatory cytokines released during infections can disrupt the ability of the hypothalamus to regulate thyroid hormone levels.” I had hepatitis at 26, and since then have struggled more with my weight–although I did, at about age 40, get back to my high school weight and maintained it for a few years. Now I can’t seem to lose weight no matter what I do (correction: if I am super conscientious and exercise quite a bit, I can lose about 1/2 a pound a month–which gets really, really frustrating). I did lose a lot of muscle tone during my very long bout of inactivity this time. I dont’ know how much that figures in.

    THanks for all you research. It’s interesting and hopefully will be helpful.

    • Congratulations on beating cancer.

      I can’t seem to lose weight no matter what.
      The past month, I fasted for a week — fluids only. Then I semi-fasted with one very light meal of a very small portion of veggies, rice, and meat and yogurt for two weeks. Then the past two weeks dropped coffee and yogurt, but ate a bit more like regular meal portions of veggies, rice/potatoes & meat/fish.

      Lost not an ounce.

      Like you, no outer eyebrows, but neither any other body hair. Hair on the head also practically gone. Yet all my tests, scans, etc. are normal.

      Very frustrating indeed.

      • erp, are you on replacement thyroid hormone? Have you experimented with dose?

        • If you mean Synthyroid, no. I just take your list of supplements, but stopped the Potassium with Iodine because I’m so unsure about what’s happening and I thought I’d try fasting, etc.

          My regular doctor sent me to an endocrinologist when my blood test showed everything in the normal range. He did a more extensive test and a scan and said my test results show I don’t need it (only a few categories deviated from the normal range and he said they weren’t significant) and wanted to send me to a dietician!!

          My roomie and my daughter both went ballistic when I mentioned meds from Mexico.

      • Erp, have you looked I to the concept of thyroid hormone resistance? Datis Kharrazian’s book lists a number of causes for thyroid hormone resistance, which makes you effectively hypothyroid even in the presence of normal thyroid hormone levels.

  22. thanks! although I don’t believe anymore that one ever beats cancer. It’s there, it lurks, ready to rear it’s head if you aren’t careful. I’ve actually heard of ovarian cancer survivors who had a recurrence after 29 years! So I am not over-confident.

    Your fasting experience sounds like my experience during Lent. Really annoying. I did read in the book Why do I still have Thyroid symptoms when my lab tests are normal? that my symptoms are more like adrenal exhaustion, which makes one thyroid resistant. I did his protocol for about three months, and did feel better, but still didn’t lose weight. But now, reading Jaminet, I’m also thinking that I have been needing more carbs. And I’m resigned that I need to do some weight bearing exercise, regularly, and rebuild the muscle that I lost while ill.

  23. Koolhydraten zijn niet de vijand - Project Gezonder - pingback on August 18, 2014 at 2:02 am
  24. Reverse T3 Carbohydrates And Diabetes | Diabetes Reversed - pingback on August 24, 2014 at 8:02 am
  25. Thank you for sharing your knowledge. I am low T3 for the first time after a month of VLC.

    What about honey for glucose instead of starch?

    • Honey is 30% glucose, 40% fructose. You’d do well to research the effects of fructose on us. It doesn’t seem to be good news. I use it VERY sparingly. Paul can correct me, but I suspect that safe starches are absorbed into the bloodstream more slowly.

      • It is a common meme within the paleo community that fruit raises blood sugar more than anything else. Fructose has a very modest effect on blood sugar.

        Of course, this might be a sign it’s no good for us. But still, for people with blood sugar issues, fructose might be better than starch.

  26. Diet, stress and anxiety - Emotional Maturity Blog - pingback on February 19, 2015 at 8:46 am
  27. Koolhydraten zijn niet de vijand - - pingback on February 21, 2015 at 8:59 am
  28. Why Paleo Is Keeping You Sick | Stress Proof Energy - pingback on March 16, 2015 at 8:00 pm
  29. Hi!

    Fascinating read. However, I do disagree on the part of becoming deficient on glucose, as your body should be able to produce the amount of carbohydrates it need from protein. These “no carb”, that have pretty much nothing to do with low carb, problems are usually caused by the lack of micronutrients you get by not eating vegetables or anything plant based. If you leave something out of your diet completely, you’re eventually going to run into deficiency in some nutrients.

    I wouldn’t recommend starch as a source of carbohydrates, as it can cause problems with your gut. Same with fructose. Half of the carbohydrates should be from glucose if you have problems with your digestion. And no grain.

    You should eat vegetables. If you have a 50g (200kCal) limit on carbs, you’re able to eat one kilogram of veggies and have a lot more micronutrients when compared to berries and grains. Here you can see it for yourself:

    Many commenters have been on very low calorie diet, which, just like yo-yoing with weighlosing and gaining, seem to cause rT3/T3 problems. Many people with the said problems are feeling better with LCHF, that at minimum should have twice the calories of VLC.
    Pretty much the typical problems with western food is the lack of vitamin D, iodine and calcium (if you don’t eat lots of dairy) and maybe zinc, that can cause thyroid and euthyroid problems. When supplementing iodine, you should supplement selenium. Copper with zinc (1 copper/10 zinc).

  30. Bisnes, If you are referring to my posts, I eat several cups of vegetables a day, cooked and uncooked, I take Vit D and my level was 61 when I had it checked a month or so ago, I take Calcium, Mag, Zinc, K2, occasional Selenium, etc. I eat quite a bit of fish and eat Nori fairly often for iodine. I think Jaminet makes an interesting case for some safe starches re: thyroid health. Yes, we can make glucose from protein, but is that the best way to go? I’m still learning what is best for me. But by low carb, I don’t mean no plants. I mean no grains except occasional rice, very few potatoes, rare beans, occasional yams. Lots of greens, cruciferous, salads, aliums, mushrooms, some root veggies like carrots and beets, tomatoes, peppers, squashes, etc. I eat some nuts, mostly cashews, occasional almonds, but many don’t agree with me.

  31. Hi Pam!

    I was actually commenting the blog post. It argued that “low carb is no carb” which is just a strawman to mislead the reader – I see that done a lot generally. You get the point if your diet’s name says “I eat carbohydrates” and then comes so
    meone to insist your diet is bad because you don’t eat carbs.

    Another thing in the post I addressed was eating starch and not counting carbs from veggies – if you’re counting carbs or even calories, this alone can cause problems, and you really should eat your carbs as sugar from veggies instead of starch from grains to have essential micronutrients. Foods with starch have high GI with low micronutrient content, and starch is fermented into glucose in your gut anyway (that’s causing problems for many).

    The post mentioned euthyroid sick syndrome, that’s common in people on very low calorie diets, like some of the commenters, but the primary cause is likely the lack of vitamins and trace elements in your diet. You can get ESS even on low carb as well – if your carbs come from high starch sources with little micronutrients.
    For example, iodine is needed for thyroid hormones, selenium is required for T4 transformation, zinc to prevent it transforming to rT3, B-vitamins in zinc metabolism, and inflammation wears out zinc.

  32. Ah, thanks for the clarification, and the info about the micronutrients.

  33. HI, I am confused. I want to eat about 1500 and no more than 1600 calories and am trying to lose weight. I have hypothyroid symptoms and had low vit D. Severely low about 9. It got back up to about 50 and I have been supplimenting with D, calcium, magnesium, b12, multi, Brazil nut for selenium, nori for iodine. I have thinning hair, dry skin, constipation, dry eyes, feel cold, knee joint pain and although I do a high energy job cleaning houses and like to dance, I think according to what I am reading I need to eat more carbohydrates. I eat low carb (avoiding starches and sugars) and I do eat veges and fats like cheese, avacadoes, nuts but mostly I eat chicken or eggs, salad, onion, lemon, mushrooms, green pepper for like fajitas and tomato and I think I might be under eating. So, I think I have been doing VLC diet even with the fats and I have a hi c-reactive protein level…probably caused due to staying up very late. I am wondering how much protein, fat and carbs I should have? I am confused because I see you say have 600 carb calories. I am not sure if that is for a 2000 cal diet? I want to aim for 1200-1600. I think I can lose weight this way. But, I know I can on 1400-1500. You mentioned your diet is a low-carb and high-fat. Typically 20-30% carb 50-65% fat. So I don’t count veges, only starchy carbs or natural sugar type carbs, right? And, what percent of protein? Does the protein need to be 600 cals then? Should the protein and carb be the same or I need 600 protein and 600 carbs? But on 1500 cals then 20% is only 300 cals, the fat at 50% is 750. So then protein is only 450 cals. But I keep seeing you say that you need to have 600 cals of protein and carb…is that together total or both need to be that. I am confused how to figure out what percentages I need to up my thyroid while doing the percentages. Another thing I wondered about is the BB do a macro cycling thing where they do low carb for two or three days then do a carb loading day. Is it better to daily have carbs or can fueling carbs every third day work? I am so glad I found this site because my hair has been thinning,my work is effected due to brain fog and fatigue and I believe this is the key. But I also know starchy carbs seem to cause me to get cravings. I can eat rice ok though or pretzels and I do ok. I also wondered is it bad to combine fat with starchy carbs or sugary carbs? Isn’t it better to eat lean protein,veges and the carbs and keep the fat away from them and eat them at other meals? Do you need to eat the carbohydrate at each meal or can you do LC meals but pick one meal to get the carbs in all at once so as to spike the insulin only once a day? Sorry so many questions but I think I finally found the answers I have been searching for since 4 years! I just found this site today. Amazing and thank you for your help and knowledge. You are really saving people’s lives. I saw about the cancer in Poland. I don’t want to get cancer. I hope you can help. Thank you for this site!

    • Hi Dori,

      Follow our food plate: but reduce the amounts proportionately to fit your appetite. Do intermittent fasting and eat enough so you are only just becoming mildly hungry at the end of the fast. Yes, you do need more carbs. Eat carbs at every meal and have at least two meals per day. They should be in the day time – no night time eating.

      Best, Paul

  34. High Carb, Low Carb, or No Carb? - Kelly Brogan MD - - pingback on December 16, 2015 at 10:04 am
  35. Hi Paul,
    I also have question on ESS.

    1) Do I fall in the category of ESS with the thyroid panel of:
    rT3 = 14,85 ng/dl (normal)
    free T3 = 0,167 ng/ dl (low!!!)
    free T4 = 0,983 ng/ dl (normal)
    TSH = 0,72 mU/l (lowerish)

    In addition I have high cortisol, low melatonine levels and a significant pregnenolone steal.

    I have been eating low carb paleo (not VLC) for 3 years now.

    2) Should I aim for a “higher” carb paleo diet. If yes, how many carbs should I eat and when?

    3) could there be other reasons than a “diet” problem.

    Thanks, really appreciate your work here.


    • Hi Nico,

      I would certainly try adopting PHD. As for your medical condition, that’s hard to evaluate without complete data, so medical professionals are better placed to diagnose conditions.

      Best, Paul

  36. A nagy szénhidrát mítosz! - Custom Body Works - pingback on February 8, 2017 at 2:25 pm
  37. I have just recently purchased the PHD book, although I am not very far through it yet. I recently spent 10 days on a low carb diet combined with intermittent fasting of between 14-17 hours. I am very overweight. This caused me to loose 8lbs which 2 weeks later are still off. I stopped this diet because my sleep apnea scores shot up from between .9- 1.5 and climbed quickly to 5.5. Also, one night I measured my pulse at only 49. The other time I tried a low carb diet (but no intermittent fasting) the apnea scores also shot up and took a few months to slowly return to normal. My doctor had suggested to transition to part t4 part NDT. Before this diet, I couldn’t tolerate the T3. It raised my pulse into the high nineties. Now, I can finally tolerate his protocol with a pulse in the 70s. I am purposely making sure that I am eating 80-100gr carbs including potatoes and rice. The apnea scores have only come down to 4.5 after 2 weeks. During the low carb diet I would eat something like, 1/2 English muffin, 1/2 cup rice, sometimes adding a 1/2 a boiled potato, in one day. I wish I understood the relationship between T3, intermittent fasting, hypothyroidism, cortisol,insulin, and cytokines, or whatever causes sleep apnea, and low carb diets. The weight just falls off of me eating low carbs while a lot of food but the apnea worsens in so very little time. It just goes to show that sleep apnea has a very high metabolic component, it is not just the fat obstructing the air passages. Does anyone know what is going on here?

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