The double burden of malnutrition is a rapidly growing global health problem. Many populations now face the combination of undernutrition (stunting, wasting, and micronutrient deficiencies) with overweight, obesity, or diet-related non-communicable diseases (NCDs) such as type 2 diabetes and cardiovascular disease (CVD). Visualize this as two simultaneous pandemics, caused by multiple, sometimes overlapping factors.
One of these overlaps is zinc deficiency. A complex, vicious cycle of chronic disease and zinc deficiency often exists in the same low-resource populations that preventive public health and nutrition strategies frequently fail to reach.
A number of chronic diseases are both exacerbated by, and can worsen, zinc deficiency. Zinc is essential for the normal metabolization of sugars and fats, among other vital roles. Inadequate zinc intake can cause stunting and increase children’s risk for diarrhea and pneumonia, and is related to the pathophysiology of diabetes and CVD in adults. Zinc supplementation can address health issues related to undernutrition—and its benefits may extend further: It also been shown, albeit inconsistently, to alleviate several risk factors for diabetes and CVD, including insulin resistance and atherosclerotic plaque-forming lipid profiles, respectively.
HarvestPlus works to improve global nutrition and health through the use of biofortified crops. The research on zinc supplementation led some of us at HarvestPlus to wonder: Could zinc-biofortified foods not only alleviate the effects of undernutrition, but also have an impact on NCDs—in effect doing double duty?
Our meta-analysis of relevant research, recently published in Advances in Nutrition, suggests that this could be the case and is worth further investigation. The analysis found that low-dose and long-duration zinc supplementation—akin to how zinc is delivered by biofortified staples—improved more risk factors for diabetes and CVD than either high-dose or short-duration supplementation. In addition, the size of the effects observed from low-dose and long-duration supplementation was greater than that for high-dose and short-duration interventions for nearly every outcome examined.
The review focused on zinc supplementation studies, since no studies to date have examined the relationship between zinc-biofortified crops (or any other food-based zinc intervention) and type 2 diabetes or CVD. While there are several important differences between supplementation and biofortification that should be considered, these findings suggest that zinc biofortification could help address both sides of the double burden of malnutrition.
The majority of meta-analyses on zinc supplementation and type 2 diabetes and CVD to date have examined the effects of doses of zinc higher than the recommended daily allowance or the recommended dose for ancillary treatment of diarrhea (10-20mg/day), and much higher than what could be delivered by zinc biofortification. For example, some studies gave over 100mg of elemental zinc per day, compared to the roughly 5-10mg of zinc per day that would be delivered by a traditional diet featuring zinc-biofortified foods. In addition, many supplementation studies last only 8-12 weeks, a significantly shorter time frame than the near-permanent adoption of a biofortified crop into the diet.
Thus, in order to understand the possible effects of zinc biofortification, we focused on low dose, long-duration zinc supplementation studies, comparing the impacts on multiple risk factors for type 2 diabetes and CVD with those of high-dose and short-duration studies. Our analysis revealed no association between dose and duration, so their effects were examined separately.
Low-dose zinc supplementation significantly improved specific risk factors for type 2 diabetes (fasting blood glucose and insulin resistance), compared with placebo. This effect was greater than for high-dose supplementation for both outcomes. For CVD risk factors, low-dose zinc supplementation also had a significant positive effect, lowering triglycerides, total cholesterol, and low-density lipoprotein cholesterol; the magnitude of the effect was again greater with low-dose supplementation than high-dose.
Findings also showed that outcomes varied based on the duration of supplementation. For type 2 diabetes risk factors, both short- and long-duration supplementation (<12 weeks vs. >12 weeks) had significant beneficial effects on fasting blood glucose, yet the magnitude of the effect from long-duration studies was more than double that of short-duration studies. In terms of CVD risk factors, short-duration supplementation benefited triglycerides only, while long-duration supplementation benefited triglycerides, total cholesterol, and low-density lipoprotein cholesterol—and to a greater extent.
Biofortification has received attention in recent years due to its positive effect on iron status and vitamin A status, and improvements in whole body functions like work capacity, cognition and behavior, and infectious morbidity. Now, the door is open for research on whether chronic NCDs could also be a target of this food-based intervention.
Our results indicate we have only just begun to understand the potential health benefits of biofortification. Further research could yield significant benefits, if this relatively simple and cost-effective strategy can not only help overlooked populations by adding essential micronutrients to diets, but also by lowering the risk for NCDs—helping to break a vicious cycle of inequity, poverty, malnutrition, and disease.
Laura Pompano is an Associate Research Fellow with HarvestPlus; Erick Boy is HarvestPlus Head of Nutrition; Jen Foley is a HarvestPlus Senior Program Manager.
