Nutritional Pearls: Can Whole Grains Affect Type 2 Diabetes?

Samantha is a 45-year-old patient who presents with a waist measurement of 37 inches, blood sugar level of 140 mg/dL, and high triglycerides. She has been diagnosed with metabolic syndrome and is looking for an easy but effective way to change her diet and improve her health.

What would you recommend?

A. Cutting out all carbohydrates.
B. Switch from refined grains to whole grains.
C. Increasing protein intake.

What is the correct answer?
(Answer and discussion on next page)

Dr. Gourmet is the definitive health and nutrition web resource for both physicians and patients. Resources include special diets for coumadin users, patients with GERD/acid reflux, celiac disease, type 2 diabetes, low sodium diets (1500 mg/d), and lactose intolerance.

Timothy S. Harlan, MD, is a board-certified internist and professional chef who translates the Mediterranean diet for the American kitchen. He is an associate clinical professor of medicine and executive director of The Goldring Center for Culinary Medicine at Tulane University in New Orleans. Dr Harlan is the 2014 co-chair and keynote speaker at the Cardiometabolic Risk Summit in Las Vegas, October 10-12. 

Answer: Whole grains reduce the risk of type 2 diabetes and heart disease.

Metabolic syndrome is a combination of abnormal lab results and body measurements that, taken together, lead to a greater risk of developing type 2 diabetes, heart disease, stroke, and heart attack. While there are multiple criteria for metabolic syndrome, the National Cholesterol Education Program Criteria considers a positive diagnosis when a patient meets 3 of the following criteria:

• Measurement around the waist ≥40 inches for men or ≥35 inches for women
• High blood pressure
• High blood sugar (>110 mg/dL)
• High triglycerides
• Low levels of high-density lipoprotein (<40 mg/DL)

For many of our patients, losing weight can help with many of these factors, as can simply improving their diet. Research into the effects of whole grains has focused on several of these criterion, including improving the waist to hip ratio (waist measurement), improving blood sugars (gauged via scores on a 2-hour insulin reaction test), and improving lipid profiles.
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Researchers in Italy and Sweden noted that these (and other) studies lack 2 elements that would make them even more useful to physicians: they do not directly compare a diet high in whole grains with a diet high in refined grains nor do they limit their participants to those who already have metabolic syndrome.

As you probably know, helping your patients avoid developing metabolic syndrome in the first place is more straightforward than treating those who have already developed the syndrome; specific research on those with the syndrome would be especially helpful.

The Research

The study¹ included 54 individuals (age 40-65) who had been diagnosed with metabolic syndrome. For a 4-week run-in period they followed their usual diet, then for another 12 weeks they were randomly assigned to one of 2 diets: a whole grain diet or a refined grain diet. These were defined as the participant's usual diet with the addition of a fixed amount of whole grain or refined grain products, provided free of charge by the researchers, to be consumed as the participant's main source of carbohydrates. The participants were instructed to maintain their starting weight throughout the study.

Researchers measured blood glucose and cholesterol levels, as well as waist measurements and serum insulin concentrations (both fasting and after eating a standardized meal for their specific diet) at the start of the study and every 4 weeks thereafter. To make sure that both groups were adhering to their assigned diet, the researchers also tested the participants' blood for alkylresorcinol concentration, a biomarker of whole wheat and rye intake.

The results: Neither group lost weight nor decreased their waist measurement over the course of the study. There were also no significant effects on fasting glucose levels, insulin, or cholesterol.

Most significantly, however, the whole grain group’s postprandial insulin response decreased dramatically: The whole grain group’s insulin concentration was 29% lower than the refined grain group. Similarly, postprandial triglyceride levels were as much as 43% lower than the whole grain group.

What’s the “Take Home”?

Encourage your patients to make the switch from more refined grains to whole grains: whole wheat or multigrain bread instead of white; brown rice instead of white rice; and oatmeal instead of grits. For those who might resist the idea of whole wheat pasta, suggest quinoa pasta—it has a similar flavor and texture to regular pasta.

You can find more suggestions for getting more whole grains in your diet at www.DrGourmet.com.

Reference:

1. Giacco R, Costabile G, Della Pepa G, et al. A whole-grain cereal-based diet lowers postprandial plasma insulin and triglyceride levels in individuals with metabolic syndrome. Nutr Metab Cardiovasc Dis. 2014;24(8):837-844.