Dietary Phytic Acid, Dephytinization, and Phytase Supplementation Alter Trace Element Bioavailability-A Narrative Review of Human Interventions

Phytic acid is abundant in plant-based diets and acts as a micronutrient inhibitor for humans and non-ruminant animals. Phytases are enzymes that break down phytic acid, releasing micronutrients and enhancing their bioavailability, particularly iron and zinc. Deficiencies in iron and zinc are significant public health problems, especially among populations with disease-associated malnutrition or those in developing countries consuming phytic acid-rich diets. This narrative review aimed to summarize findings from human intervention studies on the interactions between phytic acid, phytase, and micronutrient bioavailability. An extensive PubMed search (1 January 1990 to 8 February 2024) was conducted using MeSH terms (phytic acid, phytase, IP6, "inositol hexaphosphate," micronutrient, magnesium, calcium, iron, zinc). Eligible studies included human intervention trials investigating the bioavailability of micronutrients following (a) phytase supplementation, (b) consumption of phytic acid-rich foods, or (c) consumption of dephytinized foods. In vitro, animal, cross-sectional, and non-English studies were excluded. 3055 articles were identified. After the title and full-text review, 40 articles were eligible. Another 2 were identified after cross-checking reference lists from included papers, resulting in 42 included articles. Most studies exploring the efficacy of exogenous phytase (9 of 11, 82%) or the efficacy of food dephytinization (11 of 14, 79%) demonstrated augmented iron and zinc bioavailability. Most phytic acid-rich food-feeding studies (13 of 17, 77%) showed compromised iron and zinc bioavailability. Strong evidence supports decreased iron and zinc bioavailability in phytic acid-rich diets and significant improvements with phytase interventions. Studies of longer periods and within larger populations are needed.