Low levels of zinc, or zinc deficiency, is a common problem in children and women living in low- and middle-income countries. Cereal-based foods and legumes are rich in dietary fibre and phytates, which reduce absorption of zinc from the intestine. As people in low-income households derive majority of their nutritional intake from only these foods, they are more likely to develop zinc deficiency. Adding zinc to common staple foods, alone or in combination with other vitamins and minerals, has been proposed as an intervention to increase intake of zinc.
A team of Cochrane authors based in India, Canada, and Switzerland worked with Cochrane Public Health to evaluate the effects of fortification of staple foods with zinc on blood zinc levels and health-related outcomes in the general population above two years of age. The review includes eight studies with a total of 709 participants. Seven of the included studies were from middle-income countries in Asia, Africa, Europe, and Latin America, where zinc deficiency is likely to be a public health problem.
Analyses suggest that fortification of foods with zinc may have a marginal increase in serum zinc levels, which is an indicator of zinc status. If zinc is added to food in combination with other micronutrients, it may make little or no difference. Effects of fortification of foods with zinc on other outcomes including zinc deficiency, children’s growth, cognition, work capacity of adults, or on haematological indicators, are unknown.
“Zinc deficiency is a significant public health problem. Zinc is vital for the normal functioning of the reproductive immune and gastrointestinal systems,” said Dheeraj Shah, the lead author of the Cochrane Review. “Fortification programmes play a major role in increasing dietary uptake of some vitamins and minerals lacking in populations, especially given the low cost and long-term sustainability. Unfortunately, the practice of many countries of implementing mandatory fortification of cereal flours with zinc in combination with other micronutrients may not be the best strategy to combat zinc deficiency in these populations. The World Health Organization is going to take the findings of this Cochrane Review into consideration in their future guidelines. We hope upcoming studies will investigate the feasibility of adding zinc to other foods, such as edible oils, sugars, and beverages.”