By Diane Fennell | September 5, 2014 9:00 am
Eating a low-carbohydrate diet can have benefits for both Type 2 diabetes and heart health, according to two studies recently published in the journals Diabetes Care and Annals of Internal Medicine, respectively. An estimated 26 million Americans have Type 2, and more than one-third of adults in the United States have at least one form of cardiovascular disease.
The first study, conducted by investigators at the University of Adelaide, Australia, sought to determine the effects of a very-low-carbohydrate, high-unsaturated/low-saturated fat diet (LC) to a high-unrefined-carbohydrate, low-fat diet (HC) on blood glucose control and heart health in people with Type 2 diabetes. The researchers randomly assigned 115 overweight or obese adults with Type 2 diabetes and A1C levels (a measure of glucose control over the previous 2–3 months) of 7% or higher to one of the study diets for a total of 24 weeks.
Although both diets contained the same number of calories, the LC diet was comprised of 14% carbohydrate (with an aim of less than 50 grams per day), 28% protein, and 58% total fat, including 35% monounsaturated fat and 13% polyunsaturated fat, while the HC diet was comprised of 53% carbohydrate with an emphasis on low-glycemic foods, 17% protein, and less than 30% total fat, including 15% monounsaturated fat and 9% polyunsaturated fat. Both diets limited saturated fat to less than 10% of total calories.
In addition to consuming the assigned diets, all subjects also attended 60-minute exercise classes three days a week.
Ninety-three participants completed the study. At the end of the 24-week period, the researchers found that A1C levels had been reduced by an average of 2.6% in the LC group, compared to 1.9% in the HC group. Among participants with baseline blood glucose levels averaging 155 mg/dl or above, the blood glucose reduction was 61 mg/dl in the LC group, compared to 45 mg/dl in the HC group. (The difference in blood glucose reduction was not significant among those with lower baseline levels.) Those in the LC group also saw reduced variations in blood glucose levels and a greater reduction in triglycerides (a type of blood fat), and they were able to stop taking more of their diabetes medicines, compared to participants in the HC group.
“The findings from this study suggest that a novel eating pattern that markedly limits carbohydrates and increases protein and unsaturated fat may have more favorable therapeutic potential for optimizing the management of Type 2 diabetes and reducing cardiovascular disease risk as part of a holistic lifestyle-modification program,” said principal investigator Grant D. Brinkworth, PhD.
The study authors note that sticking to a particular meal plan for the long term is “notoriously difficult” and suggest that further study is necessary to determine whether the beneficial effects of the very-low-carbohydrate, high-unsaturated/low-saturated fat diet are sustained beyond 24 weeks.
The second study was conducted by researchers from the Tulane University School of Public Health and Tropical Medicine to determine the effects of a low-carbohydrate diet compared to a low-fat diet on body weight and heart health. The scientists recruited 148 adults without diabetes or cardiovascular disease, randomly assigning 75 of the participants to a low-carbohydrate diet (defined in this study as less than 40 grams of carbohydrate per day) and 73 of the participants to a low-fat diet (defined as less than 30% of total daily calories coming from fat and less than 7% from saturated fat).
The subjects were given the same instructions regarding dietary fiber and types of fats. They met with dietitians in individual sessions weekly for the first four weeks, then in small groups every other week for the next five months. For the last six months of the study, all participants met in small group sessions monthly.
Fifty-nine people (79%) in the low-carbohydrate group and 60 people (82%) in the low-fat group completed the yearlong study. The researchers found that, compared to those in the low-fat group, the participants in the low-carbohydrate group had significantly greater decreases in body weight and fat mass and increases in lean mass. They also had significantly greater reductions in C-reactive protein levels (a marker of inflammation), estimated 10-year risk for coronary heart disease, triglyceride levels, and ratio of total cholesterol to HDL (“good”) cholesterol. The results were found to apply to both African-American and white participants.
“Our findings suggest that people who want to lose weight and have risk factors for heart disease could consider a low-carbohydrate diet as an option to both lose weight and improve those risk factors,” noted study coauthor Tian Hu, MD, in an interview with Medscape Medical News.
Speaking with Medscape Medical News, Kasia Ciaston, MS, RD, LDN, who was not involved in the research, emphasized that the real message of the study is that getting the right balance in your diet, versus cutting out a particular macronutrient such as carbohydrate or fat, is the most beneficial to health.
For more information, read the articles “Low-Carb, Low-Saturated-Fat Diet Benefits Type 2 Diabetes” and “Heart Disease Risk: Low-Carb Diet Trumps Low-Fat Option” or see the studies’ abstracts in the journals Diabetes Care and the Annals of Internal Medicine. And to learn more about low-carbohydrate diets, see these pieces by nurse David Spero.
What have your experiences been with eating a low-carbohydrate diet? Have you noticed any beneficial effects on your health? Let us know by leaving a comment!
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