Are antinutrients harmful?
What are antinutrients? If you have never heard of them before, you are not alone. Most of us know that we need a range of different nutrients to function properly. However, few are aware of antinutrients. When it comes to what they are and whether or not they can harm our health, the answers may not be straightforward.
Antinutrients are compounds found in plant foods that interfere with the body’s ability to absorb some essential nutrients. The most common antinutrients include lectins, phytic acid and calcium oxalate. They are mostly found in grains, seeds and legumes. If your diet consists mainly of such foods, these antinutrients may be of concern.
Dr Orlando Thomas, medical doctor and functional medicine practitioner at Thomas Medical Centre, said whereas nutrients are substances that nourish plants and animals to grow and live, antinutrients earn their title because they can block the absorption of nutrients.
“Antinutrients are naturally found in animals and many plant-based foods. In plants, they are compounds designed to protect from bacterial infections and being eaten by insects,” Dr Thomas said.
“The effects of antinutrients vary among individuals based on their metabolism and how the food is cooked and prepared. Many antinutrients like phytates, lectins, and calcium oxalate can be removed or deactivated by soaking, sprouting, or boiling the food before eating,” he added.
Lectins are normally found mostly in legumes like beans, peanuts and soybeans, as well as whole grains. Lectins may interfere with the absorption of calcium, iron, phosphorus, and zinc. These antinutrients serve as the main storage form of phosphorus in seeds as they bind the minerals and stop absorption.
“Lectins are able to attach themselves to carbohydrate components of red blood cells. This in turn can make them stick together, increasing the risk of dangerous blood clots. And because lectins are resistant to digestive enzymes, they can adhere to our intestinal walls..,” Dr Thomas said.
Cooking in high temperatures, germination and fermentation have been shown to significantly reduce the lectin content in foods. However, there is evidence that lectins can be beneficial to our health, as these compounds may help destroy cancer cells, reduce the risk of type 2 diabetes, and even decrease the potency of the HIV virus.
Oxalates are found mostly in green leafy vegetables, tea, beans, nuts and beetroot. They may bind to calcium and prevent it from being absorbed in the digestive system.
“Oxalates have also been traditionally linked to an increased risk of developing kidney stones. It is important to point out that there are two types of oxalates: soluble and insoluble. Soluble oxalates have a much greater ability to form kidney stones than the insoluble ones,” Dr Thomas said.
Phytates (phytic acid) are found mostly in whole grains, seeds, legumes and some nuts. “Phytates may decrease the absorption of iron, zinc, magnesium, and calcium, reducing their bioavailability in the digestive tract. Phytic acid can also inhibit the activity of digestive enzymes necessary for the breakdown and absorption of macronutrients,” Dr Thomas said.
However, phytates are less harmful when they are ingested as a part of a balanced meal. Moreover, vitamin C has been shown to reduce the negative effects of phytates.
LOWER THE RISK
“These antinutrients affect the absorption of nutrients eaten at the same meal. Therefore, to lower this risk, it is recommended to avoid eating large quantities of foods containing antinutrients at one meal, and to eat a balanced diet throughout the day with a variety of foods,” Dr Thomas said.
Antinutrients which interfere with calcium absorption may not be suitable for individuals struggling with osteoporosis. Similarly, people with anaemia may need to avoid food compounds that could limit the iron bioavailability. In such cases, careful meal timing, dietary supplementation and thorough cooking practices, or avoiding these foods altogether, may be advised.
Some studies on vegetarians who eat diets high in plant foods containing antinutrients do not generally show deficiencies in iron and zinc, so the body may be adapting to the presence of antinutrients by increasing the absorption of these minerals in the gut.
However, other studies have shown that iron stores and blood zinc levels in vegetarians are typically below those of non-vegetarians. How well non-heme iron (the form found in plant foods) and zinc are absorbed in the body is impacted by the number of inhibitors such as phytates.
Bear in mind that antinutrients may also exert health benefits. Phytates, for example, have been found to lower cholesterol, slow digestion, and prevent sharp rises in blood sugar. Many antinutrients have antioxidant and anticancer actions, so avoiding them entirely is not recommended.