The effects of low-carbohydrate diets on cardiovascular risk factors: A meta-analysis.
Level 1 - systematic review of randomized trials
Meta-analysis of randomized controlled trials
PubMed 31935216 · doi:10.1371/journal.pone.0225348
What was done
Four electronic databases (PubMed, Embase, Medline, Cochrane Library) were searched through November 2018 for randomized controlled trials evaluating low-carbohydrate diets. Twelve randomized trials measuring body weight, blood pressure, total cholesterol, HDL-C, LDL-C, triglycerides, and fasting blood glucose were included and analyzed using fixed- or random-effects models, with stratification by intervention duration.
What was found
Compared to control diets, low-carbohydrate diets showed: - Triglycerides: -0.15 mmol/L (95% CI -0.23 to -0.07); -0.23 mmol/L (95% CI -0.32 to -0.15) for <6 months, and -0.17 mmol/L (95% CI -0.32 to -0.01) for 12–23 months. - Body weight: -1.58 kg (95% CI -1.58 to -0.75); -1.14 kg (95% CI -1.65 to -0.63) for <6 months, and -1.73 kg (95% CI -2.70 to -0.76) for 6–11 months. - Systolic blood pressure: -1.41 mmHg (95% CI -2.26 to -0.56). - Diastolic blood pressure: -1.71 mmHg (95% CI -2.36 to -1.06). - HDL-C: increase of 0.1 (unit erroneously reported in abstract as mmHg; 95% CI 0.08 to 0.12). - Total cholesterol: +0.13 mmol/L (95% CI 0.08 to 0.19). - LDL-C: +0.11 mmol/L (95% CI 0.02 to 0.19). - Fasting blood glucose: +0.03 mmol/L (95% CI -0.05 to 0.12, not significant).
Why it matters
Low-carbohydrate diets produce small favorable improvements in blood pressure, weight, and triglycerides, counterbalanced by modest increases in total and LDL cholesterol.
Limits
The total number of participants across the 12 included studies is not stated in the abstract. The abstract includes obvious typographical errors in reporting (HDL-C unit given as mmHg; lower 95% CI bound for overall weight loss identical to the point estimate). Specific carbohydrate thresholds, comparator diets, dietary adherence, and clinical cardiovascular events were not reported.
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