What are anti-nutrients?
Anti-nutrients are compounds (namedly lectins, oxalates, phytates, phytoestrogens, and tannins) naturally produced by plants as a protective mechanism against infection and insect consumption. Over time they have gained a bad wrap due to their role in reducing the block the absorption or assimilation of essential nutrients or, in some way, interfere with the physiological function of an organ. Despite this, studies also show that they can exert beneficial effects on the body (eg. the antioxidant capacity of phytates).
So should we be avoiding them and if not, what do we do about them? Read below to find out more.
Below is a compilation of the foods containing anti-nutrients and what their clinical implications may be:
But how much do they reduce the bioavailability of key nutrients?
One study showed the absorption of non-haem iron (ie. plant-based iron) and zinc are highly dependent on the amount of inhibitors (eg. phytates) also present. However, the amount it impacted absorption varied greatly (between 1-23%). In short, it is not known how much nutrient loss occurs because of anti-nutrients.
Another contributing factor that also effects nutrient absorption is not only individual metabolism, but also how the food is prepared and cooked. For example, many anti-nutrients like phytates, lectins, and glucosinolates can be removed or deactivated by soaking, sprouting, or boiling the food before eating.
Below is a list of other preparations methods may work for other anti-nutrients:
Still concerned? Here’s what else you can do.
- Eat a balanced diet throughout the day with a variety of foods to ensure you are not consuming too much of one anti-nutrient in any given meal. For example, rather than a large bowl of cereal (high in phytates), try a smaller portion of cereal with a cup of berries and a dollop of plain greek yogurt.
- Alter the time you eat certain foods to prevent them clashing with anti-nutrients. For example, you may stop drinking tea or coffee with your breakfast or afternoon snack to reduce the chances of iron being poorly absorbed. This may include speaking with your healthcare profession to re-evaluate the time you take your supplements to avoid it interacting with a meal high in anti-nutrients (NOTE: some supplements are beneficial to take with food. Always consult your healthcare professional before making any changes).
- Another strategy particularly recommended for vegans and vegetarians is to increase the amount of nutrients consumed each day (eg. vegans require 1.8x the recommended daily intake of iron and almost double the amount of zinc).
Who are most at risk?
People most at risk are people on vegan and vegetarian diets, as well as those with specific disease states like iron-deficiency anaemia, osteopenia/osteoporosis, and hypothyroidism. However, before you start limiting what you eat, speak to a healthcare professional to see what your options are as these nutrients may still be playing a beneficial role in your overall health! You may just need to monitor your food choices and eat the right combination of foods for specific meals.
My recommendation
It is important to keep in mind that whilst there are concerns about anti-nutrients limiting the bioavailability of certain foods, the same compounds are also used as therapeutic agents to assist various conditions. Therefore, avoiding anti-nutrients entirely is not recommended.
In addition, it is also important to note that these anti-nutrient compounds are often tested in isolation outside of the body (in vitro). In real life, the plant foods that contain these anti-nutrients also contain thousands of other compounds which work to counteract the anti-nutrients – particularly when these foods are prepared and cooked well. Therefore, these nutrients are expected to interact differently in the human body when consumed as part of a wholesome diet.
Overall, anti-nutrients certainly should not be the reason to reduce or limit your daily intake of fruits and vegetables. By using the techniques listed above, getting the right amount of nutrients from your diet is certainly possible. In saying that there may be some individuals who are more susceptible to the various effects of anti-nutrients. If you are concerned, please consult your healthcare professional (possible your Friendly Naturopath 😉).
References:
Harvard T.H. Chan School of Public Health. (2022). Are Anti-Nutrients Harmful?. https://www.hsph.harvard.edu/nutritionsource/anti-nutrients/#:~:text=Lectins%20in%20legumes%20(beans%2C%20peanuts,iron%2C%20phosphorus%2C%20and%20zinc.
Melina, V., Craig, W., & Levin, S. (2016). Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. Journal of the Academy of Nutrition and Dietetics, 116(12), 1970–1980.
Petroski, W., & Minich, D. M. (2020). Is There Such a Thing as “Anti-Nutrients”? A Narrative Review of Perceived Problematic Plant Compounds. Nutrients, 12(10), 2929.
