Biofortification improves micronutrient content of foods.

Zinc deficiency is common in developing countries and is often attributed to a low intake of the mineral combined with low bioavailability caused by phytate, an inhibitor of zinc absorption, in major staple foods such as rice, legumes and cereals.

Zinc deficiency can cause stunting in children, impair immune function, and adversely affect pregnancy outcomes in women. Zinc deficiency may be responsible for about 4% of the worldwide morbidity and mortality of young children. So, there's a strong need for increasing the intake of bioavailable forms of zinc.

Various strategies have been proposed to prevent zinc deficiency in at-risk populations. Fortifying products often consumed by zinc-deficient consumers is one approach, but this requires centralized processing facilities and making sure that the sensory attributes of the foods consumed are not adversely affected.

New varieties of rice with increased zinc content are being developed using conventional breeding techniques. After such varieties have been developed, they must be evaluated. However, the required studies are expensive and lengthy, and hence a very limited number of new varieties can be investigated by such methods.

Another approach would be to use biofortification to optimize the content of micronutrients in staple foods, enhancing a person's intake of micronutrients. Scientists at the University of California have developed a suckling rat pup model to study zinc absorption from various diets. They also developed an in vitro cell model from the Caco-2 cell line to assess zinc uptake. Compared to conventional breeding, this model involves less work, is more rapid, and allows a large number of breeding lines to be compared in a single experiment.

The researchers measured zinc uptake from digested samples in Caco-2 cells in culture. They also used the validated model to assess zinc absorption in vivo. They found that a biofortified rice variety contained substantially more zinc than conventional varieties. Absorbed zinc levels were significantly higher from the new variety in both the in vitro Caco-2 cell model, by 2.1-fold, and in the rat model, by 2-fold.

Results from the two models were highly correlated, indicating this cell model is likely to predict results in humans and can be used for screening purposes.

Further information. Bo L. Lonerdal, Department of Nutrition, 3217C Meyer, University of California, Davis, CA 95616; phone: [phone]; fax: [phone]; email: [e-mail].