Antinutrients “can be a source of severe food cravings that distract you from whatever you’re trying to accomplish, or they can rob you of nutrients and interfere with your hormone function, wearing down different systems in your body and causing slow performance declines over time,” claims Dave Asprey in his book The Bulletproof Diet.
Are you being robbed?
“Antinutrients are compounds in food that can interfere with the absorption of some nutrients,” says Reed Mangels, retired adjunct associate professor of nutrition at the University of Massachusetts Amherst. But they may not matter. For example:
Lectins. They’re found in whole grains, beans, and some other foods. If not thoroughly cooked, lectins can damage cells lining the digestive tract and may prevent nutrients from being absorbed. But who’s eating raw grains or beans?
Oxalate. “Spinach has some calcium, but you don’t absorb most of it because oxalate ties it up,” says Mangels. But most people don’t rely on spinach for their calcium.
Goitrogens. They’re found in soy and cruciferous vegetables like kale and Brussels sprouts, and they can interfere with the thyroid gland’s ability to take up iodine and make thyroid hormones.
“But as long as you’re getting enough iodine, which most people are, there’s no need to worry,” notes Mangels.
Phytate. The phytate in whole grains, beans, nuts, and seeds binds to zinc and iron, so you absorb less of the minerals than you do from eating fish, poultry, or meat
“Of all the antinutrients, I think about phytates the most because they’re in a lot of foundational foods for vegetarians,” says Mangels. But people eating plant-heavy diets needn’t worry.
In one study, researchers fed 21 young women a vegetarian diet or a typical U.S. diet for eight weeks each. The vegetarian diet had more beans, whole grains, and vegetables and roughly triple the phytate of the non-vegetarian diet.
The vegetarian diet contained 14 percent less zinc, and the women absorbed 21 percent less of it, so they got 35 percent less zinc on the vegetarian than on the non-vegetarian diet. But their blood zinc levels were only 5 percent lower, and they were still within the normal range.
“The study’s results suggest that the women absorbed enough zinc to replace what they excreted, and that zinc requirements can be met with a vegetarian diet rich in whole grains and legumes,” says study author Janet Hunt, retired research nutritionist at the U.S. Department of Agriculture.
The women also absorbed roughly 70 percent less non-heme iron from the vegetarian diet. (Non-heme iron, which is found in plant-based foods, isn’t as well absorbed as heme iron, which is found in meat, poultry, and seafood.)
“But the women had no signs of iron deficiency or anemia when they were on the vegetarian diet,” says Hunt. “That’s consistent with other studies that show reduced iron stores, but minimal or no difference in the occurrence of iron-deficiency anemia, in vegetarians.”
Hunt’s takeaway: “The body does a pretty good job at adapting to changes in the amount and availability of minerals in the diet to maintain an equilibrium.”
So much for robbing your body of nutrients.
What’s more, sprouting or fermenting can slash phytates.
“Fermented soy products like tempeh have less phytate than tofu,” Mangels notes. “You’ll also get less phytate from bread leavened by yeast, as opposed to muffins or biscuits made with baking powder.”
Mangels’ Bottom Line: “It’s absurd to knock whole grains, beans, nuts, and veggies out of your diet to avoid something that’s probably not harming your nutritional status in the first place.”
Photo: Joshua Resnick/stock.adobe.com.
The information in this post first appeared in the November 2019 issue of Nutrition Action Healthletter.
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