Yam Confusion: A WHOLE NEW WORLD


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 This weekend I was reading Food and Western Disease on Friday and in the intro Dr. Lindeberg talks about why some starchs like yams might be OK since humans have such a long history eating them in our ancestral African homeland, whereas potatoes are a "new world" crop and humans have only been there for at the earliest 35,000 years ago. The problem is that when I see people saying their yam dishes are paleo and potatoes aren't...they are not really eating yams, but sweet potatoes, which are Ipomoea, a NEW WORLD crop. Maybe Ipomoea has fewer anti-nutrients, but from a botanical viewpoint anti-nutrient composition is independent from ancestral history. There are many foods we have been eating a very very long time like cycad that are far more toxic than cultivated vegetables. Humans have bred vegetables to be less toxic in most cases. 

This is "New World" 

True yam (Dioscorea) is quite different from sweet potato. Most are quite large, have scratchy skin, and a white flesh, though purple yam (Ube) exists too. 

I bought one at a local market recently. They are quite cheap here because they are popular with many immigrant populations and are imported in large quantities. But after buying it, it languished some time on the counter because it was kind of intimadating. It just looked large and grizzley...I decided to try it first made by the experts- Nigerians. Luckily there is a Nigerian restaurant near me. 

Nigerians typically serve yam as "fufu," which is boiled yam pounded into a dough, though there are cassava and corn fufus too. The fufu I had was pretty bland and starchy. I don't know if I'll be seeking out African Yam in the future. I really liked the fermented cassava fufu though. It had a wonderful sour taste. 

I was going to write about how all the paleo folks eating sweet potatoes and thinking they are so authenic are a bunch of posers, but then I realized I might be endangering all the paleo manhood. You see, yams actually have much scarier plant chemicals than sweet potatoes or potatoes. For example, researchers looking at the unusual incidence of twins in some Nigerian towns found that chemicals in yams might be to blame

In 1996 Ugwonali went to Nigeria on a Downs fellowship to begin his research. After analyzing age, socioeconomic factors and other variables, Ugwonali focused on diet. Demographic and scientific studies conducted in the early 1970s pointed to white yams as the culprit in the mystery of multiple births in southwestern Nigeria. Ugwonali interviewed people about their eating habits and made his own observations. “We suspected environmental factors,” he said. “The only factor that ended up being different from the ones we controlled was yams.” In laboratories at Yale and in Nigeria, he fed rats a diet of yams and saw the average size of their litters double from about four to about nine.

“Our hypothesis is that yams act as anti-estrogens,” he said, noting that he hasn’t investigated the precise chemical link between yams and fertility and has yet to isolate an anti-estrogen from yams. Anti-estrogens fool the brain into thinking there is insufficient estrogen, causing it to release more of a hormone called gonadotrophin and increase the ovulation rate, he said.

The "most paleo sounding yam" the wild yam (Dioscorea villosa), is even more questionable, since in folk medicine its extracts are thought to be estrogenic and used for "bust enhancing." In some studies they have been shown to change sex hormone concentrations (though other studies show it is ineffective)

After yam ingestion, there were significant increases in serum concentrations of estrone (26%), sex hormone binding globulin (SHBG) (9.5%), and near significant increase in estradiol (27%).

So yeah boys, keep eatin those "paleo" "yams." They taste much better and won't give you man boobs.