What are antinutrients and should I be concerned about them?

Jun 11

To understand anti-nutrients we first need to understand nutrients. Nutrients are substances in food that our bodies need to grow and thrive. Macronutrients are needed in larger amounts: protein, carbohydrate, and fat. Micronutrients including vitamins and minerals are just as important as macronutrients; we simply need them in smaller amounts. Think of nutrients as building blocks, with each block a crucial component necessary to build a strong structure. Anti-nutrients are a natural part of some plant foods that the plants have developed to protect themselves from being eaten by insects and damaged by infections. While helpful for plants, these anti-nutrients can decrease the absorption of some nutrients in our body. However anti-nutrients don’t decrease the amount of nutrients stored in our body, or somehow cause more nutrients to be excreted. In fact, some anti-nutrients also provide health benefits!

What are the anti-nutrients?

Scientists have identified 6 classes of anti-nutrients:1. Glucosinolates are found in cruciferous vegetables like broccoli, Brussels sprouts, kale and cabbage and can block our body’s absorption of iodine which is an essential mineral for thyroid health. People with hypothyroidism are most susceptible to decreased amounts of iodine in their diet. However, glucosinolates are also well-researched antioxidants that are associated with decreased risk of some types of cancer. Human research studies do not show any negative health effects of consuming glucosinolates in cruciferous vegetables unless someone is already iodine deficient.2. Lectins in whole grains, peanuts, soybeans, and legumes such as lentils and kidney beans can decrease the absorption of calcium, iron, phosphorus, and zinc. Lectins are much more prevalent in raw or undercooked foods and can bind to cells that line the digestive tract where they may disrupt the beneficial bacteria in the gut. Lectins are also phytochemicals that provide health benefits.3. Oxalates in dark green leafy vegetables like spinach, kale, and beet greens; almonds and tea can prevent some of the absorption of calcium. Oxalates are the reason why we absorb less calcium from green leafy vegetables than we do from dairy products. We absorb about 30% of the calcium in milk, but only about 5% of the calcium in spinach.4. Phytates are found in whole grains, wheat bran, rice bran, brown rice, seeds, legumes such as pinto and navy beans, soybeans, and peanuts. Phytates can also decrease the absorption of iron, zinc, magnesium, and calcium.5. Tannins in tea, coffee, and legumes decrease iron absorption.6. Saponins in legumes and whole grains can block overall nutrient absorption. However, saponins are also beneficial phytochemicals with anti-inflammatory, anti-bacterial, and immune-boosting effects.

Are anti-nutrients something new?

Anti-nutrients are a natural part of some plant foods, and while you might not have heard much about them before, they are not a new phenomenon.

Should I worry about the impact of anti-nutrients?

1. Glucosinolates: Include iodine-rich seafood such as shrimp, cod, and tuna in your weekly food choices. Seaweed is also a good source of iodine. Iodized salt is the most widely used strategy to manage iodine deficiency.2. Lectins: Cooking, especially boiling, stewing, or even soaking in water for a few hours removes or inactivates the vast majority of lectins in legumes. Sprouting can also reduce the amount of lectins in whole grains, so you might choose sprouted wheat bread instead of regular wheat bread.3. Oxalates: Steaming dark green leafy vegetables can decrease the oxalate content by 5-53% and boiling decreases oxalate content by 30-80%.4. Phytates: Soaking, fermenting, and sprouting helps reduce the amount of phytates available in foods. Unless you consume whole grains, rice, or legumes raw, the amount of phytates in these foods is not a concern.5. Include a variety of different foods and types of foods in each meal for the highest nutrient absorption. For example, iron in dark meat chicken and red meat is absorbed at a much higher rate than the iron in dark green leafy vegetables. Vitamin C increases iron absorption from both animal and plant foods, so you might add grapefruit slices to a leafy green salad or drink orange juice with breakfast cereal fortified with iron.6. Take multivitamin/mineral supplements with water and not coffee or tea which can decrease the absorption of iron.

I thought eating more plant foods was healthy; now I hear about anti-nutrients. Should I stop eating plant foods?

There are numerous health benefits to eating more plant foods: fiber, lower amounts of unhealthy types of fat, fewer calories, important sources of phytochemicals, and antioxidants that promote health. Food recommendations to improve health overwhelmingly emphasize the importance of whole grains, vegetables, fruit, nuts, seeds, and legumes in daily food choices.Author: Lynn Grieger, RDN, CDE, CPT, CHWC

References:

The Academy of Nutrition and Dietetics. “How to Explain Basic Nutrition Concepts”. https://www.eatrightpro.org/practice/practice-resources/international-nutrition-pilot-project/how-to-explain-basic-nutrition-concepts accessed 2-26-20Harvard T.H. Chan School of Public Health. The Nutrition Source. “Are Anti-Nutrients Harmful?” https://www.hsph.harvard.edu/nutritionsource/anti-nutrients/ accessed 2-25-20Oregon State University. Linus Pauling Institute. Micronutrient Information Center. “Cruciferous Vegetables”. https://lpi.oregonstate.edu/mic/food-beverages/cruciferous-vegetables reviewed April 2017, accessed 2-27-20.Harvard T.H. Chan School of Public Health. The Nutrition Source. “Lectins” https://www.hsph.harvard.edu/nutritionsource/anti-nutrients/lectins/ accessed 2-26-20Tamara Duker Freuman. “What Are Anti-Nutrients and Should I Avoid Them?” U.S. News & World Report 6-3-2019.Denise Webb, PhD, RD. “Phytochemicals’ Role in Good Health” Today’s Dietitian. September 2013. Vol 15, No. 9 P. 70National Institutes of Health. Office of Dietary Supplements. “Iodine”. https://ods.od.nih.gov/factsheets/Iodine-Consumer/ updated 12-6-2019, accessed 2-27-2020Chai W, Liebman M. Effect of different cooking methods on vegetable oxalate content. J Agric Food Chem 2005 Apr 20;53(8):3027-30.Andrea Picincu. “What Are The Health Benefits of Saponins?” https://healthyeating.sfgate.com/health-benefits-saponins-9131.html published 12-6-2018, accessed 2-27-2020Chung KT, Wong TY, Wei CI, Huang YW, Lin Y. Tannins and human health: a review. Crit Rev Food Sci Nutr. 1998;38(6):421?464. doi:10.1080/10408699891274273 https://pubmed.ncbi.nlm.nih.gov/9759559/

Judy Doherty, MPS, PCII

Judy’s passion for cooking began with helping her grandmother make raisin oatmeal for breakfast. From there, she earned her first food service job at 15, was accepted to the world-famous Culinary Institute of America at 18 (where she graduated second in her class), and went on to the Fachschule Richemont in Switzerland, where she focused on pastry arts and baking. After a decade in food service for Hyatt Hotels, Judy launched Food and Health Communications to focus on flavor and health. She graduated with Summa Cum Laude distinction from Johnson and Wales University with a BS in Culinary Arts, holds a master’s degree in Food Business from the Culinary Institute of America, two art certificates from UC Berkeley Extension, and runs a food photography & motion studio where her love is creating fun recipes and content.

Judy received The Culinary Institute of America’s Pro Chef II certification, the American Culinary Federation Bronze Medal, Gold Medal, and ACF Chef of the Year. Her enthusiasm for eating nutritiously and deliciously leads her to constantly innovate and use the latest nutritional science and Dietary Guidelines to guide her creativity, from putting new twists on fajitas to adapting Italian brownies to include ingredients like toasted nuts and cooked honey. Judy’s publishing company, Food and Health Communications, is dedicated to her vision that everyone can make food that tastes as good as it is for you.