Adult onset type 2 diabetes (NIDDM) (Part 1)
Type 2 (once called adult onset, or noninsulin-dependent NIDDM) diabetes is a chronic condition which is increasing on a worldwide basis and has quadrupled since 1980 in parallel with increasing rates of global obesity. See here for an 18 min video on the role of diet in NIDDM and here to calculate your risk of getting this disease. Click below for a picture of the growing global problem of obesity (<1 minute):
Insulin is a hormone which tells the cells of the body to absorb glucose and use it for energy resulting in lower blood glucose concentrations. Some individuals develop insulin resistance when the body produces insulin but does not use it effectively resulting in elevated blood glucose levels, prediabetes, and then diabetes. Two major contributors to insulin resistance are excess weight (especially belly fat) and physical inactivity. Thus avoiding (or reversing) obesity and exercising (muscles have receptors for insulin so exercise results in increased insulin sensitivity) are important ways to prevent diabetes.
In addition to your blood glucose level, and excellent test for pre-diabetes or to monitor the adequacy of control in diabetics is the glycosylated hemoglobin (also called HbA1c). This number reflects the average blood glucose concentration over the previous 3 months.
An excellent randomised study was published in 2002 (video here) which randomised 3234 non-diabetic subjects (who were at risk of developing diabetes) to placebo, a lifestyle modification program with the goal of at least 7 percent weight loss (this included 150 minutes of some sort of exercise per week and a healthy, low calorie, low-fat diet which included meat, fish and dairy products) or a drug called metformin. After following subjects for an average of 2.8 years, the incidence of diabetes (cases per 100 person-year) was 11.0 in the placebo group, 4.8 in the lifestyle group, and 7.8 in the metformin group. Putting it another way, one would have to treat 6.9 persons with a lifestyle intervention (and 13.9 with metformin) to prevent one case of diabetes. Sadly however, as patients in the lifestyle group were followed for more time (up to 4 years), their glycosylated hemoglobin started to rise, likely due to lack of compliance with the intervention. At 3 years, the rate of diabetes was 29% in the placebo group, and 14% in the lifestyle group. Subsequently, subjects were followed out to a total of 15 years at which point the rate of diabetes was 60% in the placebo and 52% in the lifestyle groups. While encouraging, I would suggest that those at risk for NIDDM would want a more effective intervention.
In another study, 99 patients with NIDDM were randomized to the American Diabetes Association (ADA) Diet or a vegan low fat diet in which only 10% of calories came from fat and were followed for 74 weeks. All participants were asked not to alter their exercise habits during the study. When looking at changes in HbA1c prior to medication changes, the drop in HbA1c was significantly larger in the vegan group (-0.40%) than in the ADA diet group (0.01%)(P=0.03). Participants judged the two diets to be similar in terms of acceptability. An 18 minute video on tackling diabetes by Dr Barnard who ran this study is available here (more of his videos on diabetes here).
In 2014 a meta-analysis (statistical summary of multiple studies) summarized the results of 6 separate randomized controlled trials comparing vegetarian diets to conventional diabetic diets. Five of the vegetarian diets were free of all animal products. Overall the vegetarian diets resulted in better diabetic control that the conventional diabetic diet with a significant overall reduction in HbA1c of -0.39%.
Fortunately, national diabetes associations and guidelines are realizing the power of plant-based diets and their important role in the treatment of diabetes as described in this 5 minute video:
