Understanding Anti-Nutrients: What You Need to Know

You’ve probably heard a lot about “superfoods” and how they’re packed with nutrients that your body loves. But what about the foods that contain anti-nutrients? These little troublemakers are found in many of the same foods we eat daily. While they might sound bad, they’re not necessarily as evil as they sound. Let’s break it all down—what anti-nutrients are, where they hide, whether they’re a health concern, and what you can do about them.

What Are Anti-Nutrients?

Anti-nutrients are natural compounds found in plants that can interfere with the absorption of nutrients in your body. Some anti-nutrients block the absorption of minerals like iron, zinc, and calcium, while others can mess with your digestive system.

But don’t panic. Anti-nutrients are not all bad. In fact, many of them have health benefits, like antioxidant properties and helping to regulate blood sugar levels (1). It’s just that in large amounts, or if your diet isn’t balanced, they could have a negative impact.

Which Foods Contain Anti-Nutrients?

Anti-nutrients are mostly found in plant-based foods, which means they’re common in grains, legumes, nuts, and seeds (1). Here are some of the main offenders:

• Phytates (or Phytic Acid): Found in whole grains, legumes, seeds, and nuts. They can bind to minerals like iron, zinc, and calcium, making them harder for your body to absorb.

• Oxalates (Oxalic Acid): Found in foods like spinach, rhubarb, and beet greens. Oxalates can interfere with calcium absorption and, in high amounts, may even contribute to kidney stones.

• Lectins: Present in beans, lentils, and some grains. They can cause digestive issues if you eat them raw or undercooked, though cooking or soaking them usually removes most of the lectins.

• Tannins: Found in tea, coffee, and some fruits. They can inhibit iron absorption, particularly non-heme iron (the kind found in plant-based foods).

• Glucosinolates: Found in cruciferous vegetables like broccoli, cabbage, and kale. They can interfere with iodine uptake, which is important for thyroid function, especially if consumed in large quantities.

Should You Be Worried About Anti-Nutrients?

For most people, anti-nutrients aren’t a major concern. Unless you’re eating a very restricted or unbalanced diet, the amount of anti-nutrients in your food won’t cause significant problems. The real issue arises if your diet is heavy in foods high in anti-nutrients and low in other nutrients—this could lead to nutrient deficiencies over time.

That said, if you have specific health conditions, like kidney stones or thyroid issues, you may want to be more mindful of foods high in oxalates or glucosinolates.

Are Anti-Nutrients a Concern for Endurance Athletes?

While anti-nutrients generally aren’t a huge issue for most people, they might be a bit more of a concern for athletes, especially those who rely on plant-based sources of protein and minerals. Here’s why:

• Mineral Absorption: Endurance athletes need to replenish minerals like iron, calcium, and zinc. If you’re eating a lot of high-anti-nutrient foods, they could make it harder for your body to absorb these important nutrients, potentially impacting performance and recovery.

• Iron and Zinc Deficiency: For athletes, especially those who train hard, iron and zinc are vital for energy production and immune function. If anti-nutrients in your diet are limiting your absorption of these minerals, you could be setting yourself up for fatigue, decreased performance, and even a higher risk of illness.

How to Minimise Anti-Nutrients in Your Diet

Good news! There are a few simple ways to reduce the anti-nutrient content in your food without having to eliminate anything completely (2). Here’s how:

1. Soaking and Sprouting: Soaking beans, lentils, nuts, and seeds overnight can significantly reduce their phytate content. Sprouting can also help, as it activates enzymes that break down some of the anti-nutrients.

2. Cooking: Heat is one of the best ways to destroy or reduce lectins and some other anti-nutrients. Cooking beans and legumes thoroughly helps to make them easier to digest and reduces the risk of stomach issues. Canned and tinned pulses are cooked as part of the canning process, making them low in lectins.

3. Fermentation: Foods like sourdough bread, kimchi, and sauerkraut are fermented, and this process can break down phytates and other anti-nutrients, making the nutrients in the food more bioavailable.

4. Balance Your Diet: It’s all about variety. If you're eating a wide range of foods—especially ones high in vitamins and minerals—you're less likely to run into issues with anti-nutrients. Make sure your meals include plenty of fruits, vegetables, lean proteins, and healthy fats.

The Bottom Line

Anti-nutrients might sound a bit intimidating, but the truth is that they’re a natural part of many healthy foods. For most of us, the risks are pretty minimal—especially if we’re eating a varied diet. If you're an endurance athlete, it's worth being mindful of foods high in anti-nutrients, but don’t let them stress you out. With a few easy tricks like soaking, cooking, and balancing your diet, you can minimise their impact and keep performing at your best.

So, don’t worry about anti-nutrients taking over your diet. Just enjoy your whole grains, legumes, and leafy greens, and your body will thank you!

References

(1) M. López-Moreno, M. Garcés-Rimón, M. Miguel. Antinutrients: Lectins, goitrogens, phytates and oxalates, friends or foe? Journal of Functional Foods. Volume 89. 2022. 104938. ISSN 1756-4646. doi.10.1016/j.jff.2022.104938.

(2) Petroski W, Minich DM. Is There Such a Thing as "Anti-Nutrients"? A Narrative Review of Perceived Problematic Plant Compounds. Nutrients. 2020 Sep 24;12(10):2929. doi: 10.3390/nu12102929. PMID: 32987890; PMCID: PMC7600777.