The prevalence of type 2 diabetes is expected to rise sharply over the next three decades. Recent data from the Centers for Disease Control and Prevention shows that if current trends continue, an estimated 1 in 3 adults will be diagnosed with the disorder by 2050. Eating healthy is a key component of managing diabetes and reducing one’s risk for developing the disease. But what does eating right for diabetes actually mean?
Kathleen Kenny, MD, a clinical associate professor at Stanford, and Jessica Shipley, a clinical dietitian at Stanford Hospital & Clinics, will answer this question during a talk focused on diabetes and nutrition on Dec. 4. The Stanford Health Library event will be held at the Arrillaga Alumni Center on campus, where attendees can also have their blood glucose checked. The conversation will also be webcasted for those unable to attend in person.
To promote discussion on the topic in advance of the lecture, I reached out to Kenny and asked about nutrition principles and guidelines for patients with diabetes and others interested in how healthy eating can prevent or delay onset of the disease. In the first installment of a two-part Q&A, she explains the advantages of eating a Mediterranean diet and the importance of eating fiber-rich foods.
Are there any ways to reverse or slow the progression of pre-diabetes? Are there specific diets that may be useful to help prevent or control diabetes?
One of the most common questions my diabetic patients ask is how they can reduce or eliminate diabetes medications. Others are found to be pre-diabetic on the basis of an “A1c” or an impaired fasting glucose, and want to know how to prevent diabetes. Several randomized trials have shown that healthy diet and exercise can reverse and also delay the onset of diabetes.
One of the largest trials is the often-cited Diabetes Prevention Program, which randomized more than 3,000 patients to diet/lifestyle versus metformin versus placebo. The most effective strategy was diet and lifestyle, showing a dramatic 58 precent reduction in the rate of developing diabetes. This surpassed the drug therapy with metformin. Approximately 5 percent of patients in the lifestyle group developed diabetes annually, as compared to 11 percent in the placebo arm. Notably, there was a 16 percent reduction in diabetes risk with every 1 kg reduction in weight. This seems attainable for many patients.
There was also meta-analysis last year looking at different diets for patients with known diabetes, in terms of weight loss and improving their diabetes control. In this data compilation, the Mediterranean diet had the greatest weight loss, followed by the low carbohydrate diet. In terms of A1c reduction, the Mediterranean diet had a reduction of -0.47 percent, and the low carbohydrate -0.12 percent. But all the diets studied resulted in better glycemic control. Many studies have shown that diets high in glycemic load are linked to higher diabetes risk (particularly in overweight women), and contribute to central body fat , so it is recommended that diabetics or those at risk limit their intake of high glycemic index foods both to delay and to help control their diabetes. Additionally, there are some data suggesting that adherence and success rate may be higher for low-carbohydrate diets in patients with diabetes and insulin resistance.
A past study has suggested that eating fiber rich-foods can help in preventing type 2 diabetes. How do fiber-rich foods help to protect against developing diabetes?
There is a great deal of confusion about fiber among patients and for that matter, among health professionals. How is fiber defined? How much is recommended? The 2010 Dietary Guidelines for Americans (.pdf) recommends whole grain intake of 85 grams, whereas the average American intake is 17 grams daily. Whole grain labeling of foods is also a source of confusion for consumers, as “whole grain” claims historically have not always translated to being a good source of dietary fiber. (The current FDA definition of a whole grain product is foods that contain more than 50 percent of whole grain ingredients by weight.) Many people now avoid dietary carbohydrates, neglecting the fact that high-fiber complex carbohydrates are healthy and help with glycemic control.
Additionally, total fiber intake is correlated with reduced BMI, reduced waist circumference, and reduced obesity rates. Fiber blunts glucose rise after meals and helps with insulin sensitivity, in addition to promoting satiety and possibly having some “prebiotic “ effects on colonic flora. Fiber from whole grains is also a rich source of nutrients including iron, magnesium, selenium and B vitamins. Soluble fiber reduces LDL cholesterol, and can even reduce blood pressure, so is an essential part of a heart-healthy diet.
A Dutch cohort study in 2012 showed that in roughly 6.000 patients with diabetes, dietary fiber was linked to reduced overall mortality and cardiovascular deaths by 17 percent and 24 percent respectively, per standard deviation increase in fiber intake. In terms of prevention, a meta-analysis by De Munter et al, showed that increased whole grain consumption of 2 servings per day (40-60 g) was associated with a 21 percent reduced risk of type 2 diabetes. Similarly, in the Stockholm Diabetes Prevention Program, a prospective study of over 5000 individuals, it was demonstrated that higher fiber intake (more than 60 grams a day vs less than 30 grams per day) was associated with a 22 percent lower risk of prediabetes and diabetes, after adjustment for BMI. In summary, dietary fiber is critical in terms of weight management, helping to prevent onset of diabetes, and for those with diabetes, helping to control glucose and to reduce cardiovascular mortality.