Dietary advice for reducing cardiovascular risk.

Randomised controlled trials (parallel-group; including cluster randomised designs) enrolling healthy community-dwelling adults aged 18 years or older; less than 25% with diagnosed cardiovascular disease at recruitment; follow-up from 3 months to 4 years (median ~10 months); interventions delivered in healthcare, workplace, or community settings.

Dietary advice to reduce salt and fat intake and increase fruit, vegetables and fibre; delivered via verbal or written guidance to individuals or small groups; formats included one-to-one sessions, group sessions, posters, leaflets or other educational materials.

Dietary advice produced modest improvements in dietary intake and cardiovascular risk factors. After 3–24 months, total cholesterol decreased by 0.16 mmol/L and LDL cholesterol by 0.18 mmol/L; HDL cholesterol and triglycerides largely unchanged. Systolic blood pressure fell by 2.07 mmHg and diastolic by 1.15 mmHg; 24-hour urinary sodium excretion fell by 44.18 mmol. Fruit and vegetable intake increased by 1.25 servings/day; fibre intake increased by 5.99 g/day; total dietary fat fell by 4.49% of energy; saturated fat fell by 2.36%. Plasma α-carotene and β-cryptoxanthin rose in some trials, but with heterogeneity. Higher-intensity or longer-duration dietary advice tended to yield larger effects. The authors concluded dietary advice is effective in bringing about modest, beneficial changes in diet and cardiovascular risk factors over about 10 months, but longer-term effects are not known. The evidence base shows heterogeneity and potential biases, with many trials conducted in the USA and limited data on hard clinical outcomes.

Limitations include reliance on self-reported dietary intake with potential bias, substantial heterogeneity across trials, and variable methodological quality; dropout and incomplete reporting were common; many studies were conducted in the USA, limiting generalizability; long-term effects on cardiovascular disease events remain unproven; variation in intervention intensity and delivery complicates synthesis.