Linking zinc deficiency to the gut microbiome

“Zinc deficiency is a neglected area of research - nobody knows how many people suffer from it in South Africa. The consequences for children are terrible,” says Dr Johanita Kruger. She is a researcher at the newly-established Micronutrient Nutrition Research Programme (MNRP) at the University of Pretoria (UP).

Born and bred in Pretoria, Kruger studied both nutrition and food science at UP. Her PhD looked at ways to increase iron and zinc bioavailability in indigenous South Africa foods. Now, she is continuing that work by focussing on zinc bioavailability and how it relates to the gut microbiome – the ecosystem of bacteria and other microorganisms that live in our digestive systems. Bioavailability is an increasingly important concept in nutrition. In this context, it refers to how much of the zinc in our diet is absorbed by the body and how gut microorganisms affect that absorbtion. This is hugely important because zinc deficiency is the major cause of diarrhoea in children under five as well as being linked to a compromised immune system and cognitive impairment. It has been neglected mostly because methods available to measure zinc status are unreliable and expensive.

Nutrient bioavailability and the effects of the microbiome are important because simply increasing zinc intake will not necessarily address the deficiency. Kruger gives an example of how this could happen: “Some pathogenic microbes have a higher requirement for iron. So iron supplementation might increase growth and proliferation of pathogenic bacteria, without improving the iron deficiency.” To solve this problem, Kruger’s research will look at how probiotic and pathogenic gut bacteria respond to zinc supplementation.

She is using a laboratory system that grows bacteria on intestinal cells, mimicking the natural environment of the gut. This will also allow her to measure whether these bacteria affect uptake of zinc by the intestinal cells. The next phase of the project will investigate the intestinal microbiome of young children – the ones most affected by zinc deficiency. “Another project within the MNRP is looking at the zinc status of infants 6-24 months old. We’ll get faecal samples from them, and look at the biodiversity and profile of the microbiome.” This approach will reveal how the microbiome differs between those with enough zinc and those without. Despite zinc being included in national fortification strategies, zinc deficiency is not changing in South Africa.

Kruger hopes that her work here will help to change that. “Zinc interventions in South Africa are not having the expected outcomes; hopefully, we can give the government a different approach - one that can actually stop zinc deficiency.”

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