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Why Do Some People Develop Diabetes and Others Don’t?

By Lenny Salzberg, M.D.

May 2020

Risk factors for type 2 diabetes

Why do some people develop diabetes, and others don’t? Lifestyle and environmental factors account for the majority of the diabetes epidemic. We know that an energy-dense Western-style diet (food trucks, anyone?) and a sedentary lifestyle (thanks, COVID-19 L) are responsible for the epidemic of obesity, and that obesity often leads to diabetes. But not everyone who is obese gets diabetes, and not everyone with diabetes is obese! Why???

Genetics! Scientists have already identified 500 genes that are associated with type 2 diabetes, which together account for 20% of the predisposition to type 2 diabetes. But genes don’t explain everything. In addition to genetic factors, there are “epigenetic” factors, which are influences outside the DNA. These include things like aging, the environment, and exposure to substances during gestation. For example, prenatal exposure to famine has been associated with a higher risk of developing type 2 diabetes. Also, the children of women who have gestational diabetes are eight times more likely to develop diabetes themselves! So, if you don’t want your baby to grow up to have diabetes, don’t get pregnant during a famine, but if you must, don’t get diabetes while you are pregnant!

What are some surprising risk factors for diabetes? Many of us know about the risks incurred by lack of exercise and by drinking Mountain Dew and other sugar-sweetened beverages (e.g. sweet tea). But did you know that eating a low fiber diet, not sleeping enough, and even exposure to loud road noise are all independent risk factors for diabetes? Did you know that drinking 3 or more cups of coffee (either caffeinated or decaffeinated) is associated with a lower risk of diabetes?

The Microbiome

One of the frontiers in diabetes risk management involves our complex intestinal ecosystem: the “gut microbiome.” The gut is nearly sterile at birth. However, by age three, the gut has acquired most of the microbes that will be present through adulthood. These microscopic organisms (certain types of bacteria, fungi, and viruses) share a symbiotic relationship with the lining of the gut.

The two main types of bacteria in the gut are called Firmicutes and Bacteroidetes. Firmicutes are found predominantly in the small intestines, while Bacteroidetes reside mostly in the colon. These bacteria are involved in nutrient metabolism, drug metabolism, maintenance of the gut lining, and protection against pathogens. Dysbiosis (an imbalance of gut microbes) occurs as a result of an unhealthy diet, antibiotic treatment, or chronic infection. In one study, four days of a meat-based diet rapidly decreased the abundance of Firmicutes in the gut. Who would have thought that eating meat was bad for us? Also, it has been shown that the guts of patients with diabetes and prediabetes have fewer of the type of bacteria that change carbohydrates into short-chain fatty acids (SCFAs). SCFAs affect metabolism, energy balance, and the stability of the immune system.

Strategies to prevent and treat diabetes through manipulation of the gut microbiome are being developed. We know that you can help your own microbiome by consuming “prebiotics”, like vegetables and fruit. Probiotics, like kefir and yogurt, may also improve your gut microbiome! In the meantime, pick your parents well, eat a high fiber diet, avoid meat, drink a lot of coffee AND get enough sleep, and try not to live next to a highway! Good luck!