A recent study carried out by investigators at the Stanford University School of Medicine reveals that beta carotene (converted in the human body to a variant of vitamin A) may lower type 2 diabetes risk in Americans with a particular genetic predisposition. On the other hand, gamma tocopherol, the major form of vitamin E in the US diet, may increase diabetes risk.
Type 2 diabetes presently affects about 15 percent of the world's population, and these numbers are increasing. One-third of all children born in the US since the year 2000 are estimated to get this disease at some point in their lives, knocking decades off their life expectancies.
In this study, Stanford University scientists used a ‘big data’ approach to identify interactions between genetic variations associated with increased risk for type 2 diabetes and blood levels of substances previously implicated in its risk. They found a highly significant inverse relationship between beta carotene blood levels and type 2 diabetes risk, along with a positive association for gamma tocopherol.
Further experiments are needed to establish whether beta carotene and gamma tocopherol are protective and harmful in themselves, or whether the presence or absence of some other substance is the real underlying factor.
Along with dietary factors, many genetic risk factors for type 2 diabetes have been found. However, none of them taken alone - and not even all of them taken together - can account for type 2 diabetes prevalence.
In 2010, a study of large public databases compared people with or without high blood glucose levels to look for differences between exposure to environmental influences. This analysis identified five substances, including beta carotene, found in carrots and many other vegetables, and gamma tocopherol, relatively abundant in vegetable fats such as soybean, corn and canola oils and margarine.
Interestingly, no genetic factor had shown an impact on type 2 diabetes risk - but when paired with environmental factors, statistically significant results began to emerge.
First, in people carrying two copies of a particular genetic variant known as SLC30A4, higher beta carotene levels was associated with lower blood glucose levels. Second, high blood levels of gamma tocopherol were associated with increased risk for type 2 diabetes.
In future studies, these researchers plan to give purified beta carotene and gamma tocopherol to lab mice to identify their role in preventing or accelerating type 2 diabetes onset.
So while it’s not yet possible to say that vitamin E is bad for you, it can't hurt to eat a few more carrots.