The bioavailability of minerals is poor in legumes

This paper was published in the British Journal of Nutrition 2002 Dec;88 Suppl 3:S281-5

Study title and author:
Bioavailability of minerals in legumes.

Sandberg AS.
Department of Food Science, Chalmers University of Technology, PO Box 5401, SE 402 29 Göteborg, Sweden. ann-sofie.sandberg@fsc.chalmers.se

This study can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/12498628

Professor Ann-Sofie Sandberg is head of the Life Science Division at Chalmers University of Technology, Göteborg, Sweden. She has an extensive record in the field of phytate/bioavailability of minerals, food processing/bioavailability of nutrients and in the development of analytical methods for measuring nutrients and bioactive compounds.

Professor Sandberg reviewed the scientific evidence regarding the bioavailability of minerals in legumes.

Professor Sandberg found:
(a) The content of iron and other minerals is generally high in legumes. However, the legumes also contain antinutritional factors, such as proteinase inhibitors, lectin, raffinose oligosaccharides, saponins, polyphenols and phytate. Antinutritional factors lower the nutritional value of a food by lowering the digestibility or bioavailability of nutrients.
(b) Phytate is a well-known inhibitor of absorption of essential dietary minerals such as non-haem iron, zinc and calcium. 
(c) Some polyphenols are potent inhibitors of non-haem iron absorption.
(d) In the modern food industry, the high phytate content of soya-based infant formulas is of concern as low zinc absorption from a soya-protein-based infant formula has been found.
(e) Soya protein per se has an inhibiting effect on iron absorption.
(f) In many developing countries where diet is based on cereal and legume products, deficiency of iron and zinc, is highly prevalent.
(g) In developing countries iron deficiency, due to poor bioavailability, retards normal brain development in infants and affects the success of a pregnancy by increasing premature deliveries, as well as increased disease of mother and child at or around childbirth.
(h) Zinc deficiency prevents normal child growth and greatly weakens the immune system, leading to more infections.
(i) In industrialised countries where diet is based on cereal and legume products, deficiency of iron and zinc, is highly prevalent in certain groups such as women of fertile age, infants, adolescents and vegetarians.

The review finds that the bioavailability of minerals is poor in legumes and may lead to adverse health consequences.