Low Carbohydrate Diets & Cholesterol Levels

Critics of low-carbohydrate diets have long insisted that switching the mainstays of your meals from grains and starchy vegetables to protein will increase your levels of LDL or "bad" cholesterol. According to the American Heart Association, the ration of total cholesterol to good cholesterol should be 3.5 to 1. LDL cholesterol levels should ideally be less than 100 milligrams per deciliter of blood. Studies performed since 2008 both support and refute the idea that a low-carb diet can achieve this.

Favorable Research

A study conducted in Israel in 2008, led by Dr. Iris Shai of Ben-Gurion University and published in the New England Journal of Medicine, compared the cholesterol levels of 322 participants who were placed on either a low-fat diet, the Mediterranean Diet, or a low-carb diet over a period of two years. According to this research, the low-carb group experienced the greatest improvement in cholesterol levels, with their ratios of total cholesterol to HDL dropping favorably by 20 percent. A study led by Dr. Eric Westman, associate professor of medicine, reported on the Duke University Medical Center website, found that low-carb dieters improved their HDL cholesterol levels over a six-month period.

Limitations of Studies

The Israeli study did not include an equal number of men and women and Shai suggests that further research is necessary to determine any differences that might exist between genders. The study also controlled the diets of the participants for only one meal a day -- lunch. For breakfast and dinner, participants reported what they ate. This could possibly have resulted in omitted data that might have affected the findings.

Considerations

The leaders of the Israeli study acknowledge that they urged all three groups of dieters to get their protein from vegetable sources. Results might have been different if the low-carb subjects had consistently resorted to meat sources for protein. Researchers in the Duke University study did not allow participants to consume junk food or refined sugar, which also might have affected the outcome, but the study did not limit animal foods.

Negative Opinions

The findings of Shai and Duke University are recent and seem to refute previous research that indicated that low-carb dieters show an increase in bad cholesterol levels. Dr. Teri Hernandez with the University of Colorado told the "New York Daily News" that people on low-carb diets still have the potential of increasing their LDL cholesterol levels up to 12 milligrams per deciliter, depending on their intake of animal fats.

American Heart Association Opinion

The American Heart Association maintains that low-fat diets are best for cholesterol levels and heart health. However, the low-fat diet the association recommends is far stricter than the one used in the Israeli study. The American Heart Association recommends a diet high in fruits, vegetables, grains and fish and consuming less than 300 milligrams of dietary cholesterol per day.