Tuesday, September 8, 2009

Primal Potatoes, part 3

While thinking about the role of tubers in human evolution, I decided to revisit some of the data on tooth decay collected by Weston Price, and rediscovered something that may surprise some people.

Starch and Caries

When Price visited Alaska, he found that isolated Alaskan Indians living on native foods had 0.3% of teeth attacked by decay; isolated Kokamute Eskimos living only on native foods had 0.1% of teeth attacked by decay; and lower Kuskokwim Eskimos living only on native foods had 0.09% attacked by decay (1).

Although impressive, the Maori, an omnivorous population, had an even lower incidence of dental decay. Dr. Price quotes Pickerill, who studied both skulls and “relatively primitive” living Maori:
“In an examination of 250 Maori skulls—all from an uncivilized age—I found carious teeth present in only two skulls or 0.76 per cent. By taking the average of Mummery’s and my own investigations, the incidence of caries in the Maori is found to be 1.2 per cent in a total of 326 skulls. This is lower even than the Esquimaux, and shows the Maori to have been the most immune race to caries, for which statistics are available.” (2)

Dr. Price comments that Pickerill’s numbers report the percentages of individuals with caries; expressed in percentage of teeth attacked by dental caries, the Maori had an incidence of 0.05% or 1 in 2000 teeth. Thus, the Esquimaux—now spelled “Eskimo”—had a decay incidence at least double that of the Maori, who were living “relatively primitive” lives.

What did the Maori eat? Price reports that they ate mutton birds, seafoods, vegetables and fruits, and “Large quantities of fern root were used” (3). Bovell-Benjamin reports that “Early records have indicated that the sweet potato is a staple food source for many indigenous populations in Central and South Americas, Ryukyu Island, Africa, the Caribbean, the Maori people, Hawaiians, and Papua New Guineans” (4).

According to Cambie and Ferguson, the Maori also used taro corms (Colocasia esculenta), which they introduced to New Zealand (the Maori migrated to N.Z. from Polynesia) (5). Thus, the Maori apparently had less tooth decay than Eskimos, although eating sweet potatoes and taro corms.

When Price visited the Amazon Jungle Indians, he found an even more impressive immunity to dental decay; he did not find a single decayed tooth in the group he studied, an incidence of 0.0%. What did they eat? Price reported:
“The native foods of these Amazon Jungle Indians included the liberal use of fish which are very abundant in both the Amazon and its branches….; animal life from the forest and thickets; bird life, including many water fowl and their eggs; plants and fruits. They use very large quantities of yucca which is a starchy root quite similar to our potato in chemical content.” [Emphasis added](6)

Again, the Amazon Indians had less tooth decay than the Eskimos, while eating a diet containing large amounts of starchy roots.

Among the Australian Aborigines, Price found “dental caries or tooth decay was exceedingly rare among the isolated groups” (7). Cordain et al estimated that about 24 percent of plant foods in the Aborigine diet consisted of underground storage structures––tubers, roots, and bulbs (8). Brand-Miller and Holt report that Aborigines ate Dioscorea species (yams), Ipomoea costata (wild potato, related to Ipomoea batatas, i.e. sweet potato), and Cyperus species (native onion) (9). Tubers of I. costata range up to the size of a human head. We can eat them raw or cooked and have a slightly sweet taste.

Considering all roots and tubers eaten by aborigines, Brand-Miller and Holt report that “Some have a composition which is similar to a potato with about 15-20% carbohydrate, but others are more like a carrot with much less carbohydrate and less energy, but lots of fibre”(9). In the aborigine diet, “If plants provided 20 to 40 % of the energy in the diet (the most likely range), then plants would have contributed 22-44 g protein, 18-36 g fat, 101-202 g carbohydrate, 40-80 g fibre and 90-180 mg vitamin C in a 12500kJ (3000kcal) diet” (9) Two hundred grams of carbohydrate supplies 800 calories, only 26% of 3000 calories, so even at the high end, this does not constitute a high carbohydrate diet (compared to the 60% recommended by some), yet this intake does go higher (nearly 3 times higher) than the 75 g per day maximum suggested as a “low” carbohydrate diet by advocates of the same, such as Lutz. Nevertheless, it provides significant protein-sparing action.

For comparison, Price found 1.2 percent of teeth decayed among the Gaelics who consumed oats as a staple food, 4.6 percent among Swiss living on rye bread and dairy products, and 5.5 percent among Kikuyu living on largely vegetarian diets based on millet. Thus, the Gaelics had a tooth decay incidence twenty-four times that of the Maori. Price’s findings suggest that a primitive diet containing substantial amounts of tubers has little or no cariogenic activity compared to a diet containing substantial amounts of cereal grains.

Thus, it appears that some populations eating diets containing both animal meat and non-cereal vegetal starch have displayed a higher resistance to tooth decay than populations eating diets composed almost exclusively of animal-derived food, despite the fact that starch in the diet can increase the growth of caries-causing acidogenic bacteria in the mouth.

How To Explain These Findings?

I can presently suggest these possible explanations for these observations:
1) vegetal foods—including some starchy but non-cereal vegetal foods--provide some micronutrients that improve immunity to tooth decay, in greater quantities than provided by meat.
2) the cereal grains contain compounds that block vitamin D action and probably otherwise interfere with calcium metabolism and hence bone and tooth health, and these substances may not occur in tubers.
3) the intake of starch among the Maori and Amazon natives did not reach a threshold for increasing tooth decay
4) Eskimos' use of teeth for various tasks increased their susceptibility to caries

Regarding number 1, I have no difficulty coming up with nutrients more easily supplied in a omnivorous as opposed to a strictly carnivorous diet. Some of the essential micronutrients that play a role in maintenance of bone and tooth integrity include vitamin K1, calcium, copper, and magnesium. A strictly carnivorous, dairy-free diet tends to supply lower amounts of vitamin K1, calcium, copper, and magnesium compared to a cereal-free omnivorous diet.

Micronutrients not yet considered essential, but known to benefit bone integrity, include boron and silicon. Fruits and vegetables supply boron and silicon more abundantly than meat. In fact, sweet potatoes consumed by Maori have an extraordinary need for boron during growth, so they generously supply boron.

Regarding number 2, at least one study has shown that a diet high in cereal fiber reduces the serum plasma half life of vitamin D by nearly 30%, perhaps by fiber binding the vitamin D and reducing its reuptake and increasing its excretion (10).

1. Price W. Nutrition and Physical Degeneration. La Mesa, CA. PPNF. Pp. 61-62.
2. Ibid. P. 201.
3. Ibid. P. 262.
4. Bovel-Benjamin AC. Sweet potato: a review of its past, present, and future role in human nutrition. Adv Food Nutr Res. 2007;52:1-59.
5. Cambie RC and Ferguson LR. Potential functional foods in the traditional Maori diet. Mutat Res. 2003 Feb-Mar;523-524:109-17.
6. Price, op cit, p. 255.
7. Ibid, p. 174.
8. Cordain L, Brand Miller J, Eaton SB, Mann N, Holt SHA, Speth JD. Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets. Am J Clin Nutr 2000; 71:682–92.
9. Brand-Miller JC, Holt SHA. Australian Aboriginal plant foods: a consideration of
their nutritional composition and health implications. Nutrition Research Reviews (1998), 11, 5-23.
10. Batchelor AJ, Compston JE. Reduced plasma half-life of radio-labelled 25-hydroxyvitamin D3 in subjects receiving a high-fibre diet. Br J Nutr. 1983 Mar;49(2):213-6.


Aaron said...

Once again, thanks for these posts-- it takes time I don't have to go through all those studies!

I don't understand why the low-carb community is usually ready to pounce on any diet that goes over 100g of carb (even if carbs are kept to 20% or less of calories).

Obviously, starch is not enemy #1 (as long as you don't go way overboard in your consumption)

Fructose/vegetable oils/grains are still the most dangerous things you have to watch

Also, I gotta say that I had a slight smirk on my face from when you unseated the Inuit as the undisputed group with the best teeth(most people just assume all meat diet-- perfect teeth). Logic dictates that when you give yourself a wide range of nutrients (with inclusion of micronutrients from plants or tubers-- you are probably giving yourself the best shot at not having cavities) And its good to remember that healthy animal fats will be making up the bulk of your calories anyway-- not carbs.

Bryce said...

Fascinating as usual.

I think it's useful to look at starch as an efficient way to replenish our ready reserve energy for strenuous exertion (glycogen supplies for the glyoclytic pathway).

As such, when I can, I try to only eat tubers within about 24 hours after a rigorous workout. This works out to about 1.5 times per week, since I strength train just as frequently.

Is this a decent strategy for making the best use of tubers, while avoiding any potential effects of having loads of excess glucose floating around?

Thanks as always,

Drs. Cynthia and David said...

Thanks for the interesting post. I have been wondering ever since Stephan's posts of a few months ago whether the critical factor relates to the remineralization of dentin and enamel via calcium from the saliva. You could eat starches and sugars which would become acidic in the mouth if they stuck around for a while, and would leach calcium away from the tooth structure. But most of the time, assuming you're not constantly eating, the calcium in the saliva could move back in to remineralize the tooth structure damaged by the acid. This would be highly dependent on vitamin D levels and activity as you mention as well as calcium intake, absorption and regulation. I just wish we knew about all this years ago!


Andrew S said...

Stephan at Whole Health Source explored dental caries a bit and his posts suggests that phytate is why a grain-heavy diet would lead to more caries than a starch-heavy diet.


As for starch vs sugar vs grains, I've noticed that if I consume carbs after mid-day (especially if it's in the evening after I work out) that it's much harder to lose weight. I typically fast overnight :) so it would make sense that carbs in the morning would replenish glycogen stores rather than be stored in adipose tissue.

Aaron Blaisdell said...

These posts are great! I've suffered rampant tooth decay all of my life. I was raised on cereal for breakfast (sometimes pancakes, or waffles, or... -- you get the picture). Now I eat only eggs, yogurt, bacon, etc. for breakfast. But it's nice to be able to include potatoes in my dinner meal. In fact, I'm making some sweet potato fries tonight (using tallow skimmed off of my prior batch of bone broth). When I run out of tallow, I usually use either bacon fat, ghee, or coconut oil to make my fries.

Ryan Koch said...


What do you think about low-toxin grains, such as white rice? Are all grains on the shit-list?

Aaron Blaisdell said...

The fries last night were great. I used the white sweet potato the other Aaron mentioned in a prior post and they were delicious.

It occurred to me that there is another difference between the Eskimo on the one hand and the Maori and Amazonians on the other -- access to sunlight and therefore Vitamin D. Eskimo live in a very cold, northerly climate and must cover most of their skin with clothing much of the year.

Miki said...

Absolutely fascinating. More potatoes from now on.

2 comments on which I would like to hear your opinion:

1. The timing of the genetic change to more amylase ties up with the relative extinction of large animals which have a higher fat content (as %). According to your analysis re protein replacement it could have been a response.

2.I assume all traditional societies engaged in moderate physical activity throughout the day not just for 20-60 minutes like ourselves.
This difference, I believe explains (in part) why traditional societies could eat more carbohydrates than us and still remain insulin sensitive.Its not necessarily the total duration its more the distribution the prevents long periods of sugar and insulin surpluses and AGE formation.
Thanks for a 1st class blog.

Don said...


I agree, the Pleistocene extinctions provide an example of a non-agricultural event that would have limited fat availability and thus favored the rapid evolution of increased amylase production.

I think low meal frequency does more to limit the ill effects of insulin and glucose. Low level activity just doesn't draw down glucose stores much.

Richard Nikoley said...


Any thoughts various kinds of potatoes? That is, do regular russets, yukon gold and such fit into this picture?

Miki said...

Thanks for your reply.
Re meal frequency - you touched on something that caught my attention recently. It is the unbelievable amount of snacking that takes place among the young. Notice the shelf space that is devoted to snacks in supermarkets and other convenience stores.
If I understand correctly every food entry to our body is an inflammatory event and also most if not all of these snacks are CHO based.
In my childhood there was nothing to snack on. We had three meals and that's it. Presently I have one or two but unfortunately some of the horses already managed to escape...

Don said...


I think any potato fits the picture, but I prefer sweet potatoes.

Sanjeev said...

about the vitamin D:

Peter on Hyperlipid had a post on a hinstorical incident exactly on this subject

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