Mortality and Cardiovascular Safety
There have been several studies linking low-carb diets to increased mortality. Epidemiological studies and meta-analysis have shown an increased risk of mortality with carbohydrate intake <40%.[12][13]
However, the recent Prospective Urban Rural Epidemiology (PURE) study, a large prospective nutrition study involving over 135,000 participants across the globe, found a relationship between increased mortality and higher carbohydrate intake, and lower mortality associated with higher fat intake.[14] Until long term, randomized studies can be undertaken, the long-term effect is unclear.
Renal Function
With a potentially higher protein intake on low-carb diets, some have expressed concerns on renal function. However, depending on specific goals, athletes should ingest protein loads to optimize muscle protein synthesis (1.6 gm/kg) or for endurance sports (0.8 gm/kg).[17][18] Encouraging higher protein loads to support physical activity can also help with improving body composition and metabolic adaptations. In general, there are no data to associate high protein load with worsening kidney function in those with normal kidneys.[19]
For those with chronic kidney disease, a low or very-low-protein diet (0.2-0.8 gm/kg/day) may be recommended to prevent further renal deterioration.[20]