In recent years, some online personalities have sounded the alarm about “anti-nutrients,” claiming these compounds are a reason to avoid vegetables and other plant foods. This narrative has gained traction in certain circles, promoting fear around otherwise nutrient-dense foods (very similar to the seed oil narrative – see my previous blog post on this). This assertion is not supported by high-quality evidence. In fact, a robust body of research demonstrates the health-promoting effects of vegetables and plant-based diets, including lower risks of chronic diseases and improved longevity (Aune et al., 2017; Satija et al., 2016). However, anti-nutrients do exist, and in certain contexts they may have an impact.

What Are Anti-Nutrients?

Anti-nutrients are naturally occurring compounds found in many plant foods. They can interfere with the absorption of certain nutrients, such as minerals, under specific conditions. Common anti-nutrients include oxalates, phytates, lectins, tannins, and goitrogens. And while the name “anti-nutrient” sounds alarming, context and quantity matter greatly.

5 Common Anti-Nutrients

1. Oxalates

• Sources: Spinach, rhubarb, beets, nuts
• Evidence: Oxalates can bind calcium, potentially reducing absorption. In most healthy individuals, this is not clinically significant. However, for those with a history of calcium oxalate kidney stones, a diet excessively high in oxalates may increase risk (Taylor & Curhan, 2007).
• Takeaway: For the general population, moderate intake of oxalate-rich foods is not associated with harm. if you have a history of calcium oxalate kidney stones, be mindful of your oxalate intake, but even then, it is not the only thing driving the formation of kidney stones (more on this in a future blog post).

2. Phytates (Phytic Acid)

• Sources: Whole grains, legumes, seeds
• Evidence: Phytates can reduce absorption of minerals like iron and zinc, especially in diets low in animal-source foods. However, phytates also have antioxidant and potential anti-cancer properties. In balanced diets, mineral deficiencies are rare (Lopez et al., 2002). Soaking, fermenting, and cooking reduce phytate content.
• Takeaway: For the general population, phytate intake is not a concern. There are not many instances where someone might need to reduce or alter their phytate intake unless perhaps they were experiencing digestive troubles specifically related to the phytate itself. And while we might look at the timing of phytate intake in relation to certain minerals in the context of deficiency, it still likely wouldn’t be the first thing we address.

3. Lectins

• Sources: Beans, lentils, some grains
• Evidence: Raw or undercooked beans contain higher lectin levels, which can cause digestive upset. Cooking destroys most lectins, making properly prepared beans safe and nutritious (Vasconcelos & Oliveira, 2004). There is no evidence that lectins in cooked foods are harmful to most people.
• Takeaway: do not eat raw or undercooked beans.

4. Tannins

• Sources: Tea, coffee, some legumes and fruits
• Evidence: Tannins can reduce iron absorption, but their impact is minimal in the context of a varied diet. Tea and coffee are associated with numerous health benefits, and populations with high tannin intake do not exhibit widespread nutrient deficiencies (Chung et al., 1998).
• Takeaway: If we are concerned about dietary intake of iron being inadequate in the diet, we might consider separating coffee and tea intake from high iron foods. But if someone is actually iron deficient due to dietary inadequacy, we would generally address this with a supplement (or potentially iron infusion).

5. Goitrogens

• Sources: Cruciferous vegetables (broccoli, kale, cabbage)
• Evidence: Goitrogens can interfere with thyroid function in people with iodine deficiency. For most people with adequate iodine intake, cruciferous vegetables pose no risk and may even protect against cancer (Di Gangi et al., 2020). Cooking further reduces goitrogenic activity.
• Takeaway: Unless you are iodine deficient (which is incredibly rare in the US) or you have hyperthyroidism and are concerned about drug-nutrient interactions, you do not need to worry about goitrogens. And even in these cases, it is still not necessary to avoid goitrogens, but simply to avoid excess.

Who Should Be Cautious?

• Individuals with a history of calcium oxalate kidney stones may want to moderate high-oxalate foods.
• People with diagnosed mineral deficiencies or very limited diets should consult a dietitian.
• Individuals with thyroid conditions and low iodine intake may consider moderating raw cruciferous vegetable intake.
• People eating raw or undercooked beans – do not do this!

The Big Picture

If anti-nutrients were broadly harmful, we would expect to see negative health outcomes in populations eating plant-rich diets. Instead, the evidence overwhelmingly supports the health benefits of these foods. For most people, anti-nutrients are not a cause for concern. Only in select circumstances do they warrant special attention. As with most things, there is nuance to this discussion, but by and large, anti-nutrients are not a large concern for most folks.

All the best,

Kevin Rogers, RDN, LD

Founder | Redesign Nutrition

References:

• Aune, D., et al. (2017). Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality—a systematic review and dose-response meta-analysis of prospective studies. International Journal of Epidemiology, 46(3), 1029–1056.
• Satija, A., et al. (2016). Plant-based dietary patterns and incidence of type 2 diabetes in US men and women: results from three prospective cohort studies. PLoS Medicine, 13(6), e1002039.
• Taylor, E. N., & Curhan, G. C. (2007). Oxalate intake and the risk for nephrolithiasis. Journal of the American Society of Nephrology, 18(7), 2198–2204.
• Lopez, H. W., et al. (2002). Phytate: impact on environment and human nutrition. A Review. Critical Reviews in Food Science and Nutrition, 42(3), 225–249.
• Vasconcelos, I. M., & Oliveira, J. T. A. (2004). Antinutritional properties of plant lectins. Toxicon, 44(4), 385–403.
• Chung, K. T., et al. (1998). Tannins and human health: a review. Critical Reviews in Food Science and Nutrition, 38(6), 421–464.
• Di Gangi, I. M., et al. (2020). Cruciferous vegetables and cancer risk in humans: A systematic review and meta-analysis. Nutrients, 12(6), 1786.