Category Archives: Safe Starches - Page 2

Dieter’s Dessert: Taro Coconut Cream Soup

Since we’ve started the topic of weight loss, it seems a good time to discuss the sort of dessert one should eat while on a calorie-restricted diet.

Almost any mix of a carbohydrate with a fat can serve as a dessert. Sweeter desserts use more sugar, less starch.

The following principles can guide the design of a Perfect Health Diet weight loss dessert:

  1. Ketogenic fats, such as those in coconut oil, are the best fat source. Ketones can evade certain kinds of metabolic damage, lower blood sugar levels, contribute to metabolic recovery.
  2. Dieters should maintain their regular carbohydrate and protein consumption, since the recommended Perfect Health Diet amounts are calibrated to meet nutritional needs and malnutrition must always be avoided.
  3. Dieters should avoid fructose, a toxin. Carbs are best obtained from starches or from fructose-free sugars like dextrose (the monosaccharide of glucose) or maltose (the disaccharide of glucose).

Here’s one dessert that meets those guidelines. It’s a common Asian-Pacific dessert: Taro Coconut Cream Soup.

First, gather your starches. Here we’re dicing some (already cooked) taro that was leftover from dinner:

Tapioca pearls make another nice addition to the soup. They are white before cooking, but will become transparent when fully cooked:

Put a can of coconut milk in a pot and warm it to the boiling point. You can add up to an equal amount of water if you prefer a less thick soup:

Add tapioca pearls and taro, and simmer for 10-15 minutes until the tapioca pearls are transparent. You may need to stir from time to time to make sure nothing sticks to the bottom:

Once it’s warm and the pearls are cooked, transfer some to a bowl. Here Paul has added a bit of coconut oil for some extra fat, some lemon juice, and cinnamon:

Lemon juice is beneficial to health, for reasons we’ll explain in an upcoming series on enhancing immune function. Lemon juice adds sweetness but has only 7 calories per fluid ounce. Cinnamon increases insulin sensitivity, which is probably desirable for weight loss. Both add to the flavor of the dessert.

There it is – a Perfect Health Diet dessert for those on a diet!

Shou-Ching is not on a diet, and decided to sweeten hers with some clover honey. She also included some leftover sweet potato chunks:

An Aside About Sweet Potatoes

Last week we had a discussion about different kinds of sweet potatoes and yams. So we bought a sampling.  Here, clockwise from upper right, are an American sweet potato (orange), a Korean sweet potato (large and yellow), and a Japanese sweet potato (small and yellow). The last two are botanically yams, not sweet potatoes; they are starchy and not nearly as sweet as the American sweet potato.

The Korean sweet potato is what we eat; it has a pleasant chestnut flavor. I thought the Japanese sweet potato was excellent also. American sweet potatoes are too sweet for my taste.

What’s the Trouble With Sweet Potatoes?

We’re continuing with a series on people who have reported something going wrong when they tested some variation of the Perfect Health Diet. (The first post summarized experiences, good and bad; the second looked at difficulties suddenly adding carbohydrates to a very low-carb diet.)

The next issue was reported by Chris Masterjohn; he had trouble with sweet potatoes:

Although sweet potatoes are considered a safe starch on the Perfect Health Diet, they are not very safe for me. When I discovered how yummy sweet potato fries are, I started eating several sweet potatoes per day. Within a few days, I was limping and my neck was stiff. By the end of the week, my limp was extreme. I looked online to see if I was eating anything high in oxalates, and sure enough, sweet potatoes are loaded with them. My symptoms dramatically improved after one day off sweet potatoes and were gone the second day.

Chris’s commenter Lisa also had trouble with sweet potatoes:

I’ve been very achy since I started eating sweet potatoes daily. Why would some of us be maladapted to oxalates?… I’m wondering if after a long stint of LC/paleo eating I’ve become intolerant to oxalates or to starch in general.

Clearly sweet potatoes are not safe for everyone. What might be causing the trouble?

Fructose and Fiber as Possible Confounders

One factor to consider is that there are different varieties of sweet potato. We eat an Asian sweet potato variety which is not nearly as sweet as conventional American sweet potatoes; it has a yellow flesh and a chestnut flavor. It is botanically a yam, not a sweet potato. It looks like this (via “my super sweet twenty-six”):

Like so many modern foods, the standard American sweet potato has been bred for sweetness. Here is data from comparing 100 g of potatoes, yams, sweet potatoes, and grapes for sugar, starch, and fiber content:

Food Sugar (g) Starch (g) Fiber (g)
Potato 1.2 17.3 2.2
Yam 0.5 23.1 3.9
Sweet potato 6.5 7.5 3.3
Grapes 15.5 0.0 0.9

All have similar calories. Yams are largely sugar-free, but sweet potatoes are intermediate between grapes and potatoes in both sugar and starch content. They are sort of half fruit, half starch.

Thus, it is conceivable that sweet potatoes could trigger an issue like fructose malabsorption; or that fructose or fiber might feed certain gut infections that would not be similarly fed by potatoes.


Chris believed his problem was due to oxalate. Sweet potatoes do contain oxalate, although they are not the only plant foods which do.

In fact, by far the largest source of oxalate in the American diet is spinach. Spinach by itself accounts for over 40% of all oxalate consumed by Americans; potatoes for about 10%. [1] Wheat bran has high levels of oxalate.

Why are oxalates troublesome?  Some people have sensitivities to oxalate. Rarely, genetic defects in the enzymes that degrade oxalate cause a disease called primary hyperoxaluria; this disease afflicts 1 to 3 people in a million.  Other conditions can elevate calcium or oxalate in the urine and increase the risk of calcium oxalate kidney stones. This is especially likely in people who are deficient in magnesium or who don’t eat citrate. [2]

Another pathway by which oxalate might cause trouble is via fungal infections. Candida and other fungi form calcium oxalate crystals in tissue [3,4]; fungi appear to be responsible for the yellow-brown calcium oxalate biofilms which form on stone monuments. [5]

But the literature suggests that oxalate sensitivities are rare. If oxalate sensitivity is present, then it should manifest itself when eating spinach, wheat bran, and other oxalate rich foods. Since Chris has praised spinach and wheat recently, I wonder if it is really the oxalate that caused his trouble.


Another possibility is a class of toxins called phytoalexins.

Ordinarily, sweet potatoes are largely toxin free. But when attacked by fungus or molds, sweet potatoes generate a variety of food toxins. As two papers describe them:

Sweet potatoes contain phytoalexins that can cause lung edema and are hepatotoxic to mice. At least one of these, 4-ipomeanol, can cause extensive lung clara cell necrosis and can increase the severity of pneumonia in mice. Some phytoalexins in sweet potatoes are hepatotoxic and nephrotoxic to mice. [6]

Ipomeanine (IPN), 4-ipomeanol (4-IPO), 1-ipomeanol (1-IPO), and 1,4-ipomeadiol (DIOL) are toxic 3-substituted furans found in mold-damaged sweet potatoes. IPN and 4-IPO are the most toxic, but all produce pulmonary toxicity in cattle and rodents, and 4-IPO induces hepatotoxicity in humans. [7]

Cattle will die if fed mold-damaged sweetpotatoes:

Unfortunate bovine fatalities occurring after ingestion of mold-damaged sweetpotatoes preclude the use of the culled tubers in livestock feed. In cattle, mold-damaged sweetpotatoes induce an acute respiratory distress syndrome resulting in asphyxiation. [8]

Toxins may be present even if mold damage is not visible:

Fermentation of 6 weeks duration was observed to inadequately eliminate the lung, liver, and kidney toxicity caused by mold-damaged sweetpotatoes. In fact, fermentation exacerbated the hepatotoxicity of mold-damaged sweetpotatoes. This is also the first demonstration that sweetpotato regions lacking visible mold damage can induce lung and kidney injury … [8]


Sweet potatoes are generally considered to be one of the least allergenic of foods. However, infants sometimes do have sensitivities to sweet potato. This may reflect an immature gut flora in the infants; perhaps specific bacterial species — possibly including the oxalate-digesting Oxalobacter [9] — make sweet potatoes tolerable? If so, it raises the possibility that adults with incomplete gut flora might also have sweet potato sensitivities.

There is also the possibility of allergies to mold toxins in infected sweet potatoes.

Food Sensitivities as a Diagnostic Tool

Food sensitivities can sometimes be helpful in diagnosing certain health conditions:

  • Leaky gut. People with a leaky gut will have many food sensitivities; people with a healthy gut will have few.
  • Small bowel infections. People with infections of the small intestine will usually have a negative reaction to fructose.
  • Colonic infections. People with infections of the colon may react badly to fiber, and obtain relief on low-fiber diets.

There is a chance that oxalate may benefit fungal infections, so I suppose an oxalate sensitivity could be diagnostic for that, although in my experience fungal infections are usually slow-reacting to food and the response is rarely obvious.


In our book [p 121] we note that all plants make pesticidal toxins. Thus, no plant food can be guaranteed to be safe.

Normally, levels of pesticidal toxins are low in sweet potatoes. But it’s always desirable to inspect sweet potatoes for visible damage, and to discard any that are discolored or show other evidence of toxin production.

I confess to being puzzled as to how sweet potatoes caused Chris’s symptoms. If he tolerates spinach and wheat bran, it seems unlikely that the oxalate in sweet potatoes would be responsible. He might wish to test various foods and try to narrow down the source of his sensitivity.

For our part, we may cease listing sweet potatoes among our “safe starches” and specify yams instead, since a “safe starch” should probably be low in fructose.


[1] Taylor EN, Curhan GC. Oxalate intake and the risk for nephrolithiasis. J Am Soc Nephrol. 2007 Jul;18(7):2198-204.

[2] McConnell N et al. Risk factors for developing renal stones in inflammatory bowel disease. BJU Int. 2002 Jun;89(9):835-41.

[3] Takeuchi H et al. Detection by light microscopy of Candida in thin sections of bladder stone. Urology. 1989 Dec;34(6):385-7.

[4] Muntz FH. Oxalate-producing pulmonary aspergillosis in an alpaca. Vet Pathol. 1999 Nov;36(6):631-2.

[5] Pinna D. Fungal physiology and the formation of calcium oxalate films on stone monuments. Aerobiologia. 1993 9(2-3):157-167.

[6] Beier RC. Natural pesticides and bioactive components in foods. Rev Environ Contam Toxicol. 1990;113:47-137.

[7] Chen LJ et al. Metabolism of furans in vitro: ipomeanine and 4-ipomeanol. Chem Res Toxicol. 2006 Oct;19(10):1320-9.

[8] Thibodeau MS et al. Effect of fermentation on Sweetpotato (Ipomoea batatas) toxicity in mice. J Agric Food Chem. 2004 Jan 28;52(2):380-4. B76FN5FG89GM

[9] Hatch M et al. Enteric oxalate elimination is induced and oxalate is normalized in a mouse model of Primary Hyperoxaluria following intestinal colonization with Oxalobacter. Am J Physiol Gastrointest Liver Physiol. 2010 Dec 16. [Epub ahead of print].

Cambridge Fried Rice

CarbSane has asked for a recipe for Yang Zhou Fried Rice; Yang Zhou is a city in southern China in a leading rice-farming region.

As far as we know there is no special ingredient, though Wikipedia says that barbecued pork is a characteristic ingredient. The great thing about fried rice is that you can adjust the ingredients to your taste; use as many or as few as you like. So, here is our recipe — let’s call it Cambridge Fried Rice.

The key steps are to “fry” (really, warm and coat in oil) the ingredients separately, to get a good diffusion of oil throughout the rice and food.

Here’s how it’s done. As always, click on images to enlarge.

First, gather ingredients. You’ll need oils, eggs, long-grain rice (short-grain rice sticks together and doesn’t work as well), plus other ingredients of your choice.  Here are peas, carrots, scallions, and shrimp — we’ll also use mushrooms:


Next, scramble some eggs. Use whatever oil you like, we think eggs go well with butter:

Set the scrambled eggs aside, add new oil to the pan (now we’ll use olive oil), and add any of the miscellaneous ingredients that need cooking:

Again, set these ingredients aside:

The long-grain rice should have been cooked, but long enough ago that it has had time to cool and dry. Traditionally, fried rice uses leftover rice — cooked earlier in the day or the previous day.

Add oil (now we’ll use coconut oil) and rice to the pan, stir until rice has soaked up the oil and is uniformly coated:

Now return all the ingredients to the pan, mix, and add spices to taste:

In this case we added salt and pepper, divided the fried rice in two, and added turmeric to one half. (Soy sauce can be added to hot oil when frying vegetables and meat, but it’s not necessary.)


We haven’t measured weights or counted calories, but it’s fairly obvious that this is a fat-rich (oils, egg yolks), carb-moderate (rice), protein-light (shrimp, egg whites) recipe with vegetables for good measure — essentially, the Perfect Health Diet macronutrient ratios.

This is the basic recipe, add spices or ingredients to your taste!

If you would like another view of Yang Zhou Fried Rice, from a professional chef, here’s a video:

Cooking with Rice, I: Chicken Soup

Since many Americans and Europeans are not familiar with how to use rice, we thought it would be nice to offer some ideas, mainly drawn from Asian cooking.

(The zero-carb dangers series is continuing, but as it’s science heavy I thought mixing in a food post would be fun.)

We make a soup every weekend and have a bowl to start dinner most days of the week. Chicken soup is a classic winter dish. We have a brief recipe in the book, but here is a variant. In the book recipe, the chicken is pulled out before it disintegrates, the meat and skin pulled from the bones and returned to the soup. Here, the chicken is left in the soup and cooked much longer to create a thicker and more nutritious broth. The downside is that many small chicken bones are left in the soup.

The Recipe

We like a garlic-salt-and-pepper flavor. Garlic is very important for the flavor of the soup; use at least 12 cloves, I prefer 20. Slice each clove in half so that the flavor seeps into the broth more easily.

Use enough water for the chicken to float but not swim:

For the most nourishing broth, simmer 2-3 hours. Skim off scum that rises to the top, but don’t skim off fat. If you wish a soup with less protein, remove the chicken breast meat after one hour, returning the rest of the chicken to the soup; the breast meat can be used for other dishes, like chicken salad.

Meanwhile, you can pre-soak some uncooked rice in water. This helps the rice open in the soup:

After 30 minutes or more of soaking, pour off this water to remove starch and surface contaminants, then add the rice to the soup. Cook another 1 hour. With shorter cooking, the rice remains intact; with longer cooking the rice releases starch into the broth for a thicker broth.

By this time the chicken should be falling apart. Use a spoon to break it to small pieces. Add salt and pepper and other spices to taste. In the last half hour, you can add any vegetables you wish to cook in the soup.

You can also add vegetables after the soup is finished, for a crunchier texture. In this case we added cilantro, carrots, and scallions:

Finally, after cooking is done and just before eating, you can add fat sources to hot soup for a richer taste. We use egg yolks or heavy cream. I rather like cream with turmeric. Here is how it looks with three egg yolks: