Many people eat foods like white bread and white rice, which are refined low-nutrient foods, while avoiding healthful foods because they are afraid of the “anti-nutrients” in whole grains, beans, certain types of nuts, etc. This is upsetting to me because it’s absolutely unnecessary to avoid these foods. The notion that these foods are unhealthy is an absurdist interpretation of food science and nutrient absorption in the human body.
The compounds classified as anti-nutrients include:
- Glucosinolates in cruciferous vegetables, which can prevent the absorption of iodine
- Lectins in legumes and whole grains can interfere with the absorption of calcium, iron, phosphorous, and zinc
- Oxalates in green leafy vegetables, rhubarb, bran cereals, beets, berries, chocolate, and tea bind to calcium and prevent absorption
- Phytates in whole grains, seeds, legumes, and some nuts, which can decrease the absorption of iron, zinc, phosphorous, and calcium
- Saponins in legumes and whole grains, which can interfere with the absorption of many nutrients
Anti-Nutrients are Rarely a Problem
Many of the anti-nutrients, including phytates, lectins, and glucosinolates, can be removed or deactivated by soaking, sprouting, or boiling the food before eating it. The glucosinolates in raw cruciferous vegetables such as kale or broccoli are generally not a problem unless you consume enormous amounts of these uncooked vegetables and have both an underlying thyroid disorder and an iodine deficiency.
Don’t Eat Raw Kidney Beans
According to an informative article from the Harvard T.H. Chan School of Public Health, eating raw or undercooked kidney beans is dangerous. It can cause nausea, vomiting, stomach upset, diarrhea, bloating, and gas. A compound in raw and undercooked kidney beans, phytohaemagglutinin, causes red blood cells to lump together. Lectins can bind to cells in the lining of the gastrointestinal tract and disrupt the breakdown of absorption of minerals. Because lectin proteins bind to cells for an extended period, they can potentially cause an autoimmune response. They hypothetically could play a role in inflammatory diseases such as rheumatoid arthritis and type 1 diabetes.
Luckily, this isn’t a problem that modern people will have. How many of you have ever sat down to eat a beautiful bowl of uncooked kidney beans? I’m going to go out on a limb here and guess none. Lectins are destroyed by cooking, especially boiling or stewing, or soaking in water for several hours. Dried beans are generally soaked for several hours and then boiled for several hours. Beans prepared this way, or canned beans, are mostly lectin-free.
Don’t Rely on Rhubarb for Calcium
Similarly, the oxalates in food aren’t much of a concern as long as they aren’t your only source of calcium. If you drink a glass of milk or eat a container of yogurt, you’ll make up for the amount of calcium that you didn’t absorb from your spinach salad.
Don’t Bother Soaking Your Corn and Rice Before Eating Them
Some people are soaking their whole grains, such as wheat, corn, barley, rice, and oats, to remove the phytic acid before eating them. Phytic acid is only in the hull or bran of grain, so, for example, white rice contains none. Deficiency from eating phytic-acid containing foods is unlikely to occur in any developed nation. People in developing countries who subsist mainly on rice have some reason for concern. If you eat dairy products, meat, and seafood, or certain vegetables, including kale and bok choy, there isn’t much risk that the small amounts of phytic acid in your whole grains will cause you to become mineral deficient. If you consume animal protein, onions, or garlic with your phytate-rich whole grains, nuts, or seeds, you will absorb more zinc. Phytate’s effect on iron absorption also varies by the specific type of food. For instance, the iron in pea protein is absorbed much more readily than the iron in soy protein. Vitamin C rich foods such as tomatoes or oranges also increase the absorption of iron.
People With Certain Medical Conditions Should Talk to a Registered Dietitian
Some experts recommend avoiding large amounts of foods containing anti-nutrients in one sitting. Individuals with specific deficiencies, such as osteoporosis or iron-deficiency anemia, might want to pay some attention to their food choices and to alter the timing of eating foods with anti-nutrients; for example, maybe eating salad and yogurt at different meals to maximize calcium absorption. It is possible that people with an underlying digestive problem, such as irritable bowel syndrome, are more likely to have reactions to foods that contain anti-nutrients.
Most Vegetarians are Not Deficient in Iron or Zinc
However, vegetarians, who consume a diet very high in anti-nutrients, are not often deficient in iron and zinc. It is hypothesized that the vegetarian body adapts to the presence of anti-nutrients by increasing the absorption of the minerals in the intestines.
Why You Should Actually Try to Eat More Anti-Nutrients
Phytates have been found to reduce cholesterol levels, slow digestion, prevent sharp rises in blood sugar, and prevent osteoporosis. Lectins similarly slow down digestion and the absorption of carbohydrates, thereby avoiding sharp increases in blood glucose levels and insulin.
Many anti-nutrients have also been found to have antioxidant and anticancer actions. Lectins are being studied for their ability to cause cancer cell death. Researchers are also investigating if non-toxic, low amounts of lectins might stimulate gut cell growth in patients who are unable to eat food for an extended period. Lectin-containing foods, including beans, peas, nuts, and whole grains are associated with decreased risk of heart disease, type 2 diabetes, and overweight. The same foods that contain the “anti-nutrients” are rich sources of many nutrients, including potassium, magnesium, fiber, vitamin C, vitamin A, and many more. Fiber itself prevents the absorption of some nutrients, but no one would ever say that we should eat a fiber-free diet.