Meta-analysis of 174 trials: moderate carb cuts improved heart markers, keto raised LDL more
A meta-analysis of 174 randomized trials with 11,481 adults found that carbohydrate-restricted diets changed lipids, blood pressure and weight; ketogenic diets gave larger LDL increases.
A meta-analysis published in The American journal of clinical nutrition pooled 174 randomized trials with 11,481 adults from 27 countries. It compared carbohydrate-restricted diets (up to 45% of energy from carbohydrates) with higher-carbohydrate diets and assessed cardiovascular and anthropometric outcomes sciencedirect.com
The American journal of clinical nutritionsciencedirect.comOpen source ↗. The team, led by Texas A&M University, used random-effects models and split the diets into ketogenic, low-carb and moderate-carb groups.
Lipids, blood pressure and inflammation
Carbohydrate-restricted diets reduced triglycerides by 15.11 mg/dL (95% CI: -18.76 to -11.46). Systolic pressure fell by 2.05 mmHg (95% CI: -3.13 to -0.96) and diastolic pressure by 1.26 mmHg (95% CI: -1.94 to -0.57). Several lipid ratios and the inflammatory markers C-reactive protein and tumor necrosis factor-alpha also decreased.
HDL cholesterol rose by 2.92 mg/dL (95% CI: 2.10 to 3.74). LDL cholesterol and total cholesterol also increased modestly, by 4.81 (95% CI: 2.58 to 7.05) and 4.32 mg/dL (95% CI: 1.66 to 6.97) respectively. All measured body composition markers showed significant reductions.
Diet type and replacement macronutrient
Moderate-carbohydrate diets offered balanced benefits. Ketogenic diets produced greater weight loss, but also greater increases in LDL and total cholesterol sciencedirect.com
The American journal of clinical nutritionsciencedirect.comOpen source ↗. Trials in which carbohydrates were replaced by a combination of fat and protein showed the most comprehensive improvements.
The effects were most pronounced in women and in people with overweight or obesity. Longer interventions amplified the changes in lipid ratios and inflammatory markers. According to the authors, potential adverse effects, including LDL elevation and lean mass loss, warrant clinical monitoring.
The review mostly measured risk indicators such as cholesterol and blood pressure. It cannot establish that any level of carbohydrate intake prevents more heart attacks or strokes. Most trials came from North America and Europe, the quality of the foods chosen could not be fully accounted for, and several comparisons relied on relatively few trials.
