Beta-carotene may reduce diabetes risk

According to new US research beta-carotene may lower the risk of type-2 diabetes in people with a common genetic variation, while vitamin E (gamma-tocopherol) may increase risk of developing the disease.

The study analyzed existing data on potential interactions between 18 gene variants previously associated with increased risk for type-2 diabetes and blood levels of substances previously implicated in type-2 diabetes risk (1). The results showed that people carrying two copies of one of the 18 predisposing gene variants seem to have a statistically highly significant association between increased beta-carotene blood levels and lower risk of type-2 diabetes. In addition, people with these gene variants may have a higher disease risk when combined with high blood levels of gamma-tocopherol – the major form of vitamin E in
the American diet. High blood levels of alpha-tocopherol – another form of vitamin E that predominates in most supplements – showed no harmful interaction with the predisposing gene variant.

The researchers commented that further experiments should clarify whether beta-carotene and gamma-tocopherol are, respectively, protective and harmful themselves, or merely markers whose levels in the blood correspond with the presence or absence of some other substance, process or defect that is a true causal factor. Beta-carotene and gamma-tocopherol seem to interact with the same gene variant (SLC30A4) coding for a protein abundant in insulin-producing islet cells of the pancreas, where the protein aids the transport of zinc into those cells. This, in turn, triggers the release of insulin, whose adequate secretion by the pancreas and efficient uptake in muscle, liver and fat tissue counters the dangerous buildup of glucose in the blood and, in the long run, the onset of type-2 diabetes. The genomes of some 50 to 60 percent of the US population carry two copies of that very gene variant, which previous studies have shown to confer a slightly increased risk of contracting type-2 diabetes. The scientists noted that the new findings reassure that beta-carotene has protective effects evidence already exists to suggest it reduces the risk of developing type-2 diabetes.

1. Chirag J. et al. Systematic identification of interaction effects between genome- and environment-wide associations in type 2 diabetes mellitus. Human Genetics. Published online January 2013.