You Asked, I Answered
Filed under: General Health, Nutrition
In my recent blog on the awesomeness of potatoes, I got some interesting and common questions from people that I thought should be shared more fully than on the comments section.
Q. Good information and makes a good case to eat potatoes. However, how much of the nutrients do you think are in the skins – the part that most Americans don’t eat? Haven’t done the research myself but I’ve heard most of the nutrients are in the skin.
A. The idea that most of the nutrients are in the skin is a myth. While it is true that some nutrients, and much of the fiber is in the skin, the flesh itself contains plenty of nutrients and some fiber too. I honestly don’t think it makes too much of a difference if you eat the skin or not. If you enjoy the skin, eat it, if you hate it, don’t eat it. It isn’t worth forcing it down and making your meal less enjoyable for extra gram or two of fiber.
Q.Great articles, as always, Brian.
I’m wondering what your thoughts are on the glycoalkaloids and saponins found in both potatoes and quinoa? For someone with no known auto-immune of GI dysfunction, are the levels contains in these foods even worth worrying about? For myself and most of my clients, I’m a big fan of adding in quality starchy carbs in the form of peeled yams, sweet, red and white potatoes. Quinoa seems like a nutritional powerhouse, but the saponin levels are much higher than that of peeled potatoes. Cause for concern, or overblown hype?
A. The glycoalkaloids of potatoes are tightly controlled and monitored in the US. The most common varieties have incredibly low quantities of glycoalkaloids.
The level that is generally recognized as safe is 200 mcg/g. As you can see, only the flesh of one variety exceeds this level – snowden. I have never seen these sold anywhere, and I believe they are only used for potato chips.
It is absolutely true that glycoalkaloids can be toxic at high doses, and can cause low birth weight, liver damage, anemia, weight loss, diarrhea, and even death. However, pretty much every plant on the planet (and some animal foods too) contain some form of toxin. These defenses are how they prevent themselves from being eaten. There are dangerous levels of these toxins, but we are adapted to tolerating them in small doses.
On top of that the research that showed the ill effects from glycoalkaloid consumption used amounts that far exceed anything we could get from normal potato consumption. Stephan also explained this in great detail in one of his posts, so I am just going to post what he laid out, because it was incredibly well done:
“What happens when you feed normal animals normal potatoes? Not much. Many studies have shown that they suffer no ill effects whatsoever, even at high intakes (1, 2). This has been shown in primates as well (4, 5, 6). In fact, potato-based diets appear to be generally superior to grain-based diets in animal feed. As early as 1938, Dr. Edward Mellanby showed that grains, but not potatoes, aggravate vitamin A deficiency in rats and dogs (7). This followed his research showing that whole grains, but not potatoes, aggravate vitamin D deficiency due to their high phytic acid content (Mellanby. Nutrition and Disease. 1934). Potatoes were also a prominent part of Mellanby’s highly effective tooth decay reversal studies in humans, published in the British Medical Journal in 1932 (8, 9).
Potatoes partially protect rats against the harmful effects of excessive cholesterol feeding, when compared to wheat starch-based feed (10). Potato feeding leads to a better lipid profile and intestinal short-chain fatty acid production than wheat starch or sugar in rats (11). I wasn’t able to find a single study showing any adverse effect of normal potato feeding in any normal animal. That’s despite reading two long review articles on potato glycoalkaloids and specifically searching PubMed for studies showing a harmful effect. If you know of one, please post it in the comments section.”
In my opinion the skin and the glycoalkaloids are not worth worrying about. There might be conditions where they aggravate the symptoms, like inflammatory bowel disease, but in an otherwise healthy person, the choice is yours.
As for the saponin content of quinoa, that is another example of a bitter plant-based toxin to prevent itself from being eaten. In most commercially available quinoa’s in the US, the saponin content has already been removed, so this is not an issue whatsoever. Another concern is the phytic acid issue in all grains and seeds. Phytic acid is an anti-nutrient that binds to minerals and prevents their absorption.
Quinoa does contain phytic acid, but the same process used to remove the saponins also removes about 30% of the phytic acid (reference), so this isn’t a big issue either. If you want to ensure that their are no saponins, and decrease the phytic acid content even further, you can germinate or sprout the quinoa.
To do so, you simply soak the quinoa in water for 2-4 hours, and then rinse well in running water in a fine strainer. Quinoa has a very short germination period, which is convenient. This step will probably improve your quinoa even more, though it isn’t necessary if your quinoa has already been washed and/or rubber to remove the saponin content.
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Posted on January 19th, 2011 by Brian St. Pierre
1 Comment
April 26th, 2011 at 6:19 pm
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