Low-Carbohydrate Diets are Not Created Equal

Low-carbohydrate diets have been among the most popular weight-loss strategies of the last several decades. But, new research published in the Annals of Internal Medicine indicates that the type of low-carbohydrate plan one chooses affects not only the waistline, but the risk of mortality.

In a large, prospective, observational study, researchers evaluated whether the type of low-carbohydrate diet — plant-based or animal-based (indicating the primary source of fats and proteins) — influences mortality. The study participants included more than 85,000 women (aged 39 to 59 years at baseline) from the Nurses’ Health Study and 44,000 men (aged 40 to 75 years at baseline) from the Health Professionals Follow-up Study; they had no heart disease, cancer, or diabetes at the beginning of the study. The women were followed from 1980 to 2006, and the men from 1986 to 2006.

Based on self-recorded diet histories, participants were assessed a score representing animal- or plant-based low-carbohydrate eating habits. In general, total low-carbohydrate scores were associated with a modest increase in overall mortality, but the finding was not significant. Comparing extreme deciles of scores, higher plant-based scores were associated with lower all-cause mortality and cardiovascular mortality, but not lower cancer mortality; higher animal-based scores were associated with all-cause mortality, cardiovascular mortality, and cancer mortality. The analysis adjusted for multiple confounding factors.

Many factors influence cardiovascular risk and mortality, other than choice of low-carbohydrate foods, but this is not the first study to reveal risk factors associated with carbohydrate-restricted diets. Several noteworthy studies in the last few years have shown an increased risk of death associated with low-carbohydrate consumption. While carbohydrate-restricted diets are generally effective at achieving weight loss, approximately one-third of people following such a diet experience increased cholesterol levels. Specifically, low-density lipoprotein (LDL) cholesterol — the “bad” cholesterol — tends to decrease as body weight decreases, but low-carbohydrate diets are the exception to this rule.

The findings of the Annals study are limited by the fact that it is an observational design, so conclusions regarding causality cannot be drawn with a high degree of certainty. Also, the sample population, though large, is not representative of the general population. However, Atkins-diet believers may want to think twice before skipping the carbs in favor of an entire plate of bacon. Healthy diets are about more than simply playing “20 questions” at meal time — animal, vegetable, or carbohydrate? A balanced diet with an appropriate proportion of carbohydrates, fats, and proteins is essential to health and longevity.

References

Barnett TD, Barnard ND, & Radak TL (2009). Development of symptomatic cardiovascular disease after self-reported adherence to the Atkins diet. Journal of the American Dietetic Association, 109 (7), 1263-5 PMID: 19559147

Fung TT, van Dam RM, Hankinson SE, Stampfer M, Willett WC, & Hu FB (2010). Low-carbohydrate diets and all-cause and cause-specific mortality: two cohort studies. Annals of internal medicine, 153 (5), 289-98 PMID: 20820038

Halton TL, Willett WC, Liu S, Manson JE, Albert CM, Rexrode K, & Hu FB (2006). Low-carbohydrate-diet score and the risk of coronary heart disease in women. The New England journal of medicine, 355 (19), 1991-2002 PMID: 17093250

Kennedy ET, Bowman SA, Spence JT, Freedman M, & King J (2001). Popular diets: correlation to health, nutrition, and obesity. Journal of the American Dietetic Association, 101 (4), 411-20 PMID: 11320946

Sjögren P, Becker W, Warensjö E, Olsson E, Byberg L, Gustafsson IB, Karlström B, & Cederholm T (2010). Mediterranean and carbohydrate-restricted diets and mortality among elderly men: a cohort study in Sweden. The American journal of clinical nutrition, 92 (4), 967-74 PMID: 20826627

Trichopoulou A, Psaltopoulou T, Orfanos P, Hsieh CC, & Trichopoulos D (2007). Low-carbohydrate-high-protein diet and long-term survival in a general population cohort. European journal of clinical nutrition, 61 (5), 575-81 PMID: 17136037