Whole grains reduce your risk of Type 2 diabetes and heart disease

Metabolic syndrome, for those who might not be long-time readers of our columns, 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. The clinical definition of metabolic syndrome is applied to those meeting three of the following criteria:

• Measurement around the waist greater than 40 inches for men or 35 inches for women.
• High blood pressure.
• High blood sugar. (This is defined as a fasting blood sugar over 110 mg/dL.)
• High triglycerides. (This is another type of fat that circulates in the blood.)
• Low levels of high-density lipoprotein (HDL Cholesterol - the good cholesterol)(a level under 40).

For many people, losing weight can help with many of these factors, as can improving your diet. Research into the effects of whole grains has focused on several of these criterion, including improving your Waist to Hip ratio (waist measurement) (Bite, 12/15/10), improving your blood sugars (improving your score in a 2-hour insulin reaction test) and improving cholesterol scores(Bite, 12/19/07). Researchers in Italy and Sweden noted that these (and other) studies lack two elements that would make them even more useful to physicians like myself: 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 might guess, helping my 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 is especially helpful.

The study, published in Nutrition, Metabolism & Cardiovascular Diseases (2014;24(8):837-844), included 54 men and women between the ages of 40 and 65 who had been diagnosed with metabolic syndrome. For a four-week run-in period they followed their usual diet, then for another 12 weeks they were randomly assigned to one of two 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.

At the start of the study and every four weeks thereafter the participants spent a day in the lab so that their blood glucose, waist measurements, and cholesterol scores could be tested, as well as measuring their blood insulin concentrations both fasting and after eating a standardized meal for their diet (whole grain or refined grain, as appropriate). To make sure that both groups were adhering to their assigned diet, the researchers also tested the participants' blood for alkylresorcinol concentration, which is a biomarker of whole wheat and rye intake.

Unsurprisingly, neither group lost weight or decreased their waist measurement over the course of the study. Nor were there significant effects on fasting glucose levels, insulin, or cholesterol.

More significantly, however, the whole-grain group's postprandial (after eating) insulin response decreased significantly: the whole-grain group's insulin concentration was 29% lower than the refined-grain group. Higher insulin levels after eating is a known risk factor for type 2 diabetes and heart disease. Similarly, postprandial triglyceride levels were also significantly lower (as much as 43%) in the whole-grain group, with higher levels another possible risk factor for heart disease.

What this means for you

This is a particularly well-designed study that could only be improved by a longer duration and a larger group of participants. It clearly shows that more whole grains in the diet can help you avoid developing type 2 diabetes and heart disease - even if you already have been diagnosed with metabolic syndrome. Here are some simple suggestions for getting more whole grains in your diet.

First posted: July 30, 2014