Anti-nutrients: Should They Be Avoided?
Posted:
2024-07-08
What’s happening?
Anti-nutrient compounds like lectins, oxalates, goitrogens, phytates, phytoestrogens, and tannins are naturally found in plant foods and act to protect plants from their surrounding environment (1-2). Some claims have linked several negative health effects, such as altered gut function, inflammation, food poisoning (lectins), greater risk for kidney stone formation (oxalates), altered thyroid function or goiter (goitrogens), hormone imbalances (phytoestrogens), and reduced absorption of iron (tannins) and other minerals (phytates) (1-2). This increased attention towards anti-nutrients has led some influencers to suggest eating fewer plant foods, often promoting other popular diets in their place, such as the paleolithic or carnivore diet (3). Should individuals avoid anti-nutrients, and the plants that bear them? Two dietetic practicum students along with the PEN® Team revisited the topic of anti-nutrients from a previous Trending Topic on Lectins to try to answer this question.
What does the evidence say?
Evidence on the negative health effects of anti-nutrients is inconsistent and limited (4-6). A 2020 narrative review assessed existing clinical evidence and the impact of certain ‘anti-nutrients’ (1):
Plant-based compound | Food sources | Impact |
Tannins | Many foods, particularly tea coffee, cocoa and fruits (e.g. grapes, berries, stone fruits) | Reduced absorption of nonheme iron of the foods they are eaten with. |
Lectins | Common beans (e.g. kidney, pinto, black and white) and soybeans | Can cause food poisoning if consumed without being properly prepared or cooked (e.g. soaking, boiling).
Evidence does not suggest lectins cause altered gut function or inflammation as claimed. |
Phytates | Grains and legumes | Mixed evidence; shown to reduce bioavailability of minerals and have antioxidant properties. |
Phytoestrogens | Soy products | Not enough evidence to support the negative health claims |
Goitrogens | Brassica vegetables (e.g. broccoli, Brussels sprouts, kale), kelp |
In cases where evidence for anti-nutrients and their negative health effects may exist, some measures can be taken to minimize harm:
- Use proper preparation and cooking methods, such as soaking and boiling or consuming canned beans (1,3).
- Consume a diverse and varied diet to reduce the effects of isolated plant-based compounds (1,2).
- Purchase processed plant-based foods that have been fermented or milled (1,3). For example, consuming more fermented vegetables shows improved iron bioavailability when consuming high phytate meals and polished rice contains less phytate compared to wild rice (1.2-3.7mg/g compared to 12.7-21.6 mg/g (1)).
Additional human clinical trials on the beneficial properties of anti-nutrients are needed (2).
How can dietitians support clients who have concerns about anti-nutrients?
Consumption of anti-nutrients can be part of a regular eating pattern (1). Dietitians can provide education on the following when supporting their clients’ questions about anti-nutrients:
- The risk of harm from anti-nutrients is low (1,3).
- Plant foods containing anti-nutrients also contain many beneficial nutrients, resulting in a net positive effect on health, including the prevention and treatment of chronic diseases such as cardiovascular disease and type 2 diabetes (1, 7-9).
- The risk of harm from anti-nutrients can be minimized with proper preparation and cooking techniques (1,3).
- Provide specific counselling for individuals at greater risk for harm from anti-nutrients, including those with iodine or iron deficiencies, or kidney stones, who may need to moderate their intake of some anti-nutrients (1,4-6).
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Written by Amanda Berger and Vianca Wagan, dietetic practicum students in the Nutrition Communication, Master of Health Science Program at Toronto Metropolitan University. Reviewed by the PEN Team.
References
- Petroski W, Minich DM. Is There Such a Thing as "Anti-Nutrients"? A Narrative Review of Perceived Problematic Plant Compounds. Nutrients. 2020;12(10):2929. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/32987890/
- López-Moreno M, Garcés-Rimón M, Miguel M. Anti-nutrients: Lectins, goitrogens, phytates and oxalates, friends or foe? Journal of Functional Foods. 2022;89:104938. https://doi.org/10.1016/j.jff.2022.104938 Abstract available from: https://www.sciencedirect.com/science/article/pii/S1756464622000081
- Dietitians of Canada. Diet Composition – Paleolithic Diet Background. In: Practice-based Evidence in Nutrition® [PEN]. 2023 Aug 22 [cited 2024 Jun 7]. Available from: https://www.pennutrition.com/KnowledgePathway.aspx?kpid=23246&trid=23407&trcatid=38. Access only by subscription. Click Sign Up on PEN login page.
- >Dietitians of Canada. What dietary and lifestyle factors are associated with an increased risk of developing kidney stones in individuals with no previous history of kidney stones? In: Practice-based Evidence in Nutrition® [PEN]. 2023 Jan 23 [cited 2024 Jun 7]. Available from: https://www.pennutrition.com/KnowledgePathway.aspx?kpid=7550&pqcatid=146&pqid=7443. Access only by subscription. Click Sign Up on PEN login page.
- Dietitians of Canada. What foods and nutrients decrease iron absorption and inhibit iron status? In: Practice-based Evidence in Nutrition® [PEN]. 2023 Sep 25 [cited 2024 Jun 7]. Available from: https://www.pennutrition.com/KnowledgePathway.aspx?kpid=403&pqcatid=145&pqid=22692. Access only by subscription. Click Sign Up on PEN login page.
- Dietitians of Canada. What is the impact of tea and coffee consumption on non-heme iron absorption and is there an effect on iron status among healthy adults? In: Practice-based Evidence in Nutrition® [PEN]. 2023 Sep 25 [cited 2024 Jun 7]. Available from: https://www.pennutrition.com/KnowledgePathway.aspx?kpid=403&pqcatid=145&pqid=22676. Access only by subscription. Click Sign Up on PEN login page.
- Dietitians of Canada. Are diets higher in total dietary fibre (including whole grains, cereals, vegetables, fruit and legume/pulse fibre) recommended for primary or secondary cardiovascular disease (CVD) prevention? In: Practice-based Evidence in Nutrition® [PEN]. 2019 Dec 10 [cited 2024 Jun 7]. Available from: https://www.pennutrition.com/KnowledgePathway.aspx?kpid=674&pqcatid=146&pqid=28050. Access only by subscription. Click Sign Up on PEN login page.
- Dietitians of Canada. How do vegetarian and/or vegan diets impact the risk of developing type 2 diabetes and the management of type 2 diabetes? In: Practice-based Evidence in Nutrition® [PEN]. 2020 Dec 07 [cited 2024 Jun 10]. Available from: https://www.pennutrition.com/KnowledgePathway.aspx?kpid=2709&pqcatid=145&pqid=8874. Access only by subscription. Click Sign Up on PEN login page.
- Dietitians of Canada. Are vegetarian and/or vegan diets recommended for the primary or secondary prevention of cardiovascular disease? In: Practice-based Evidence in Nutrition® [PEN]. 2020 Jun 26 [cited 2024 Jun 10]. Available from: https://www.pennutrition.com/KnowledgePathway.aspx?kpid=2709&pqcatid=146&pqid=2689. Access only by subscription. Click Sign Up on PEN login page.