http://news.mc.duke.edu/news/article.php?id=9412
People who followed a low-carbohydrate diet for six months raised their
good cholesterol and lowered their triglycerides, changes that can help
lower the risk of heart disease, Duke University Medical Center
researchers found.
The Duke study compared the effects of a low-carbohydrate diet, which
included nutritional supplements, with a low-fat, low-cholesterol,
low-calorie diet. The two diets improved cardiac risk in different
ways, said lead researcher Eric Westman, M.D., associate professor of
medicine at Duke University Medical Center.
The low-carb diet improved HDL, or good cholesterol levels, and lowered
triglycerides, the researchers found. The reduced fat diet lowered
total cholesterol levels and triglyceride levels. Both diets brought
down blood levels of small LDL particles, the form of bad cholesterol
most likely to lead to hardened arteries, they found.
The results appeared early online November 16, 2005 in the
International Journal of Cardiology and will appear in print in 2006.
The research was funded by an unrestricted grant from the Robert C.
Atkins Foundation. The study authors have no financial interest in
Atkins Nutritionals, Inc.
"I think the emerging science shows different diets improve cardiac
risk in different ways. We are moving from a one-size-fits-all approach
to considering many different diets to fit the many different types of
cardiac risk," Westman said.
Overall, both diets had positive effects on cholesterol, Westman said.
The triglyceride levels improved significantly in both groups, falling
74.2 points for the low-carb group and 27.9 points for the low-fat
group. People on the low-carb diet showed an increase in HDL
cholesterol by 5.5 points, a positive change, while those following the
low-fat diet did not have a significant change. LDL cholesterol levels
did not change significantly in either group but small LDL particles
decreased 17.4 points for the low-carb dieters and 19.2 points for the
low-fat dieters, a similar improvement. The total cholesterol of the
low-fat dieters saw a 13.7 point decline over 6 months but did not
change significantly in the low-carb dieters.
The 120 study participants were randomly assigned to either the
low-carbohydrate diet or the low-fat, low-cholesterol, low-calorie
diet. All were between 18 and 65 years old and in generally good
health, with a body mass index (BMI) between 30 and 60, indicating
obesity, and a total cholesterol level of more than 200 mg/dL. None had
tried dieting or weight loss pills in the previous six months.
The low-carbohydrate group was permitted daily unlimited amounts of
animal foods (meat, fowl, fish and shellfish); unlimited eggs; 4 oz. of
hard cheese; two cups of salad vegetables such as lettuce, spinach or
celery; and one cup of non-starchy vegetables such as broccoli,
cauliflower or asparagus. They also received daily nutritional
supplements -- a multivitamin; essential oils including flax seed oil,
borage oil and fish oil; and chromium picolinate. There were no
restrictions on total calories, but carbohydrates were kept below 20
grams per day at the start of the diet.
The low-carbohydrate diet appears to have a favorable effect on cardiac
risk, Westman said. "While the low-carbohydrate group received extra
nutritional supplements, and experienced greater weight loss, these
differences did not fully account for the changes in cardiac risk
factors that we saw," he said.
The low-fat, low-cholesterol, low-calorie group followed a diet
consisting of less than 30 percent of daily caloric intake from fat;
less than 10 percent of calories from saturated fat; and less than 300
milligrams of cholesterol daily. They were also advised to cut back on
calories. The recommended daily calorie level was 500 to 1,000 calories
less than the participant's maintenance diet -- the calories needed to
maintain current weight.
Westman noted that the diets have one often-ignored similarity. "It's
possible that the common denominator of these diets is what they're not
eating - both diets did not allow refined sugar or junk food,"
Westman said.
Study participants were encouraged to exercise 30 minutes at least
three times per week, but no formal exercise program was provided. Both
sets of dieters had group meetings at an outpatient research clinic
regularly for six months.
Co-authors include William Yancy, Jr., M.D., Maren Olsen, Ph.D., Tara
Dudley and John Guyton, M.D., all of Duke.