Antinutrients: The Lesser-Known Compounds in Our Food

When it comes to food, many are familiar with macronutrients like proteins, carbohydrates, and fats, and even micronutrients such as vitamins and minerals. Yet, antinutrients, naturally occurring compounds found in various plants and grains, are much less understood. Despite their negative connotation, antinutrients play complex roles in our health and nutrition.

What are Antinutrients?

Antinutrients are substances that can interfere with the absorption or utilisation of nutrients in the body. They are commonly found in plant-based foods, especially in seeds, grains, legumes, and tubers. The term "antinutrient" stems from their potential to hinder the absorption of essential nutrients in the digestive system. Examples of antinutrients include lectins, phytates (or phytic acid), oxalates, tannins, saponins, and protease inhibitors (1).

Why do Plants Produce Antinutrients?

Plants have evolved over millions of years to deter pests, microbes, and herbivores. Antinutrients serve as a natural defence mechanism, preventing premature germination or consumption by predators. For instance, lectins can cause digestive distress in animals, discouraging them from eating those specific plants again. Similarly, saponins, when consumed in large quantities, can be toxic to fish, making them an effective deterrent in aquatic environments (2).

Antinutrients and Human Health

1. Nutritional Impacts

   • Phytates: Phytic acid, mainly found in grains and legumes, can inhibit the absorption of essential minerals like iron, zinc, magnesium, and calcium. Over-reliance on foods high in phytic acid, without adequate mineral intake from other sources, can increase the risk of deficiencies (3).

   • Oxalates: Found in foods like spinach, rhubarb, and beetroot, oxalates can bind to calcium forming insoluble crystals, which may contribute to kidney stone formation in susceptible individuals (4).

   • Lectins: Consumed in large amounts, some lectins can disrupt the gut lining and reduce the absorption of nutrients. For instance, improperly prepared kidney beans can lead to lectin poisoning, characterized by nausea, diarrhoea, and vomiting (5).

2. Potential Health Benefits

   Contrary to the name, not all effects of antinutrients are negative. They can have beneficial health implications when consumed in moderation:

   • Phytates: Recent research has indicated that phytic acid might possess antioxidant properties and can play a role in cancer prevention (6).

   • Tannins: Found in tea, wine, and some fruits, tannins have antioxidant properties that can protect against cellular damage (7).

   • Protease Inhibitors: Found in foods like soybeans, these antinutrients can suppress the activities of enzymes that play a role in hypertension and cancer (8).

3. Individual Variability

   It's worth noting that the impact of antinutrients can vary among individuals based on genetic factors, gut microbiome composition, and overall diet.

Mitigating the Effects of Antinutrients

Traditional food preparation techniques can significantly reduce antinutrient levels:

• Soaking: Immersing grains and legumes in water can decrease their phytate content.

• Fermentation: Fermenting foods, as in making sourdough or kimchi, can reduce phytic acid and lectin levels (9).

• Cooking: Properly cooking foods, especially legumes, can deactivate most harmful lectins and other antinutrients (10).

Conclusion

Antinutrients, though seemingly detrimental from their name, offer a more nuanced narrative. They can pose challenges in nutrient absorption but also provide potential health benefits. With proper food preparation, their adverse effects can be mitigated. As with many aspects of nutrition, understanding and balance are key.

References

1. Kumssa, D. B., Joy, E. J., Ander, E. L., Watts, M. J., Young, S. D., Walker, S., & Broadley, M. R. (2015). Dietary calcium and zinc deficiency risks are decreasing but remain prevalent. Scientific reports, 5, 10974.

2. Sparg, S. G., Light, M. E., & Van Staden, J. (2004). Biological activities and distribution of plant saponins. Journal of ethnopharmacology, 94(2-3), 219-243.

3. Gibson, R. S., Bailey, K. B., Gibbs, M., & Ferguson, E. L. (2010). A review of phytate, iron, zinc, and calcium concentrations in plant-based complementary foods used in low-income countries and implications for bioavailability. Food and nutrition bulletin, 31(2_suppl2), S134-S146.

4. Taylor, E. N., & Curhan, G. C. (2007). Oxalate intake and the risk for nephrolithiasis. JASN, 18(7), 2198-2204.

5. Pusztai, A., Ewen, S. W., Grant, G., Peumans, W. J., Van Damme, E. J., Rubio, L., & Bardocz, S. (1990). Relationship between survival and binding of plant lectins during small bowel passage and their effectiveness as growth factors. Digestion, 46(4), 308-316.

6. Schlemmer, U., Frølich, W., Prieto, R. M., & Grases, F. (2009). Phytate in foods and significance for humans: food sources, intake, processing, bioavailability, protective role and analysis. Molecular nutrition & food research, 53(S2), S330-S375.

7. Scalbert, A., Johnson, I. T., & Saltmarsh, M. (2005). Polyphenols: antioxidants and beyond. The American journal of clinical nutrition, 81(1), 215S-217S.

8. Kennedy, A. R. (1995). The evidence for soybean products as cancer preventive agents. Journal of Nutrition, 125(suppl_3), 733s-743s.

9. Reddy, N. R., & Sathe, S. K. (2002). Food Phytates. CRC Press.

10. Vasconcelos, I. M., & Oliveira, J. T. A. (2004). Antinutritional properties of plant lectins. Toxicon, 44(4), 385-403.