Low-carb diets not safe, increase all-cause and cause-specific mortality, study says

Low-carb diets should be avoided because they may actually increase the risk of premature death from all causes, as well as risk of death caused by coronary heart disease (CHD), stroke, and cancer, according to study results presented at the European Society of Cardiology Congress 2018.

“Low carbohydrate diets might be useful in the short term to lose weight, lower blood pressure, and improve blood glucose control, but our study suggests that in the long-term they are linked with an increased risk of death from any cause, and deaths due to cardiovascular disease, cerebrovascular disease, and cancer,” said senior author Maciej Banach, MD, PhD, professor, Department of Hypertension, Medical University of Lodz, Lodz, Poland.

According to the Centers for Disease Control and Prevention (CDC), obesity affects roughly 93.3 million Americans, and this translates to an obesity prevalence of 39.8% (2015-2016). In addition, medical conditions related to obesity—including cardiovascular disease, stroke, type 2 diabetes, and some cancers—are the leading causes of preventable, premature death.

As many as 45 million Americans go on diets each year, and spend approximately $33 billion on weight-loss products. Diets low in carbohydrates and high in protein and fat have become de rigueur. Since the Atkins diet, many such diets have evolved, including the ketogenic, Paleo, and Dukan diets. But their long-term effects remained largely unstudied—until now.

For this prospective study, Dr. Banach and colleagues gathered data from a nationally representative sample of 24,825 subjects (mean age: 47.6 years; 51% female) from the US National Health and Nutrition Examination Survey (NHANES). They assessed the associations between low-carb diets, all-cause deaths, and deaths from CHD, cerebrovascular disease, and cancer.

Subjects with the lowest carbohydrate intake had a 32% higher risk of all-cause mortality over a mean follow-up of 6.4 years, they found. The risk of death from CHD was also increased by 51%, cerebrovascular disease by 50%, and cancer by 35% in those on low-carb diets compared with high-carb diets. Finally, Dr. Banach and colleagues found that, with each decreasing quartile of carbohydrate intake, risks of all-cause and cause-specific deaths over 6.4 years rose and were significant even after adjusting for confounding factors.

They also studied the link between all-cause mortality and low-carb diets according to BMI index (≥ 30 kg/m² vs [obese] < 30 kg/m² [non-obese]) and age (≥ 55 years vs < 55 years), and found that the strongest links occurred in those who were not obese and older.

Results from a large meta-analysis of seven prospective studies confirmed the results from Dr. Banach et al. For this meta-analysis, researchers included 447,506 subjects who were followed for an average of 15.6 years. In subjects on low-carb diets, risk for all-cause mortality increased by 15%, cardiovascular mortality by 13%, and cancer mortality by 8% compared with those on high-carb diets.

“Our study highlights an unfavourable association between low carbohydrate diets and total and cause-specific death, based on individual data and pooled results of previous studies. The findings suggest that low carbohydrate diets are unsafe and should not be recommended,” concluded Dr. Banach.