22 January 2022, Bangladesh: Bangladeshi preschool children who ate biofortified zinc rice every day for nine months measured significantly taller than children who ate traditional rice for the same duration in a randomized, controlled study recently published in the American Journal of Clinical Nutrition. Optimizing linear growth has lifelong physical and cognitive benefits.
Zinc is essential for healthy human growth and development and a properly functioning immune system, particularly during infancy, childhood, adolescence, and pregnancy, when zinc requirements are relatively high. However, foods rich in zinc like animal-based foods are often out of reach or sparsely eaten among many poorer populations, contributing to widespread zinc deficiency. By breeding added zinc into rice, the aim of biofortification is to make zinc more readily available in the diet through a staple food already eaten in abundance.
The study with 520 children aged 12-36 months was conducted in the rural Bangladesh county of Badarganj, where the prevalence of zinc deficiency is very high: 78 percent of the children enrolled in the study were zinc deficient at the start and nearly 60 percent were stunted (short for their age)—clear evidence of the need for nutrition and other inventions to improve health and development.
Among the young children who ate zinc rice, the study found no detectable significant changes in the levels of zinc deficiency as measured by the concentration of zinc in the blood (plasma zinc).
There are numerous possible reasons for the lack of effect on zinc status. Recurrent and frequent infections and intestinal inflammation are common in this population, ailments that can impair zinc metabolism and therefore inhibit added dietary zinc from making an impact. Also, plasma zinc concentration (the recommended indicator to measure population zinc status) may be inadequate for detecting zinc status change associated with dietary interventions delivering smaller amounts of zinc relative to supplements. For example, the quantity of zinc rice consumed by children in the study (239 grams per day of cooked rice, on average) added a modest 1 mg of extra zinc to the diet per day compared to traditional rice.
“This study shows the limitations of adequate zinc status measurement,” said Roelinda Jongstra, a nutritional scientist and lead author of the study. “Results also might have been different within a population eating more rice, and therefore more zinc.”
Stunted growth has lifelong negative effects on individual and societal health and livelihoods. The improvements in growth experienced by children in the study who ate zinc rice are very encouraging, yet these effects were unlikely due to the zinc rice alone. Direct food-based zinc interventions are necessary, but as these study findings demonstrate, they address symptoms of a socioeconomic and environmental problem that requires holistic improvement to sustainably combat lower linear growth and stunting.
Rice is the major source of food for over three billion people worldwide, including most Bangladeshis. This study shows that enrichment of rice with zinc through conventional plant breeding offers a sustainable approach to improve zinc intakes in populations that depend on rice for most of their diet.