The WHO estimates that over 60% of cardiovascular heart disease and 40% of ischaemic stroke in developed countries are due to total blood cholesterol levels in excess of the theoretical minimum of 3·8 mmol/l.
Reduction of serum LDL-cholesterol by about 5–6% has the potential to reduce cardiovascular heart disease risk by 7–12 %, whereas a 3% increase in HDL-cholesterol has the potential to lower the risk by 6–9%.
Current guidelines recommend diet as a first-line therapy for patients with elevated blood cholesterol concentrations. Although what constitutes an optimal dietary regimen remains a matter of controversy. Among the foods being examined to lower blood lipids are soya products.
In October 1999, the US Food and Drug Administration approved labeling of foods containing soya protein as protective against CHD: ‘the inclusion of at least 25 g of soya protein/d as part of a diet low in saturated fat can help reduce blood cholesterol’.
In 2012, the European Food Safety Authority concluded that ‘a cause and effect relationship has not been established between the consumption of isolated soya protein and a reduction in blood LDL-cholesterol concentrations’. The last published meta-analysis involved studies completed between 1996 and 2008. In the past 6 years, nine additional clinical trials (involving 668 people) on the effects of soya products on lipids have been completed. Based on the availability of more recent high-quality trials, the objective of this review was to re-examine the conclusion that soya protein has proven beneficial effects on blood cholesterol.
A total of sixty-two articles with a total of 2670 subjects (aged 28–83 years) were included in this new meta-analyses. The average intake of soya protein was 30 g/d (range: 14–50 g/d).
Intake of soya products resulted in:
* a significant reduction in serum LDL: –4·83 (95 % CI –7·34, –2·31) mg/dL
* a significant reduction in serum TAG: –4·92 (95 % CI –7·79, –2·04) mg/dL
* a significant reduction in serum TC concentrations: –5·33 (95 % CI –8·35, –2·30) mg/dL
* a modest, but highly significant increase in serum HDL: 1·40 (95 % CI 0·58, 2·23) mg/dL
In conclusion, this new meta-analyses showed that an intervention with soya proteins increases serum HDL concentration (3%) and results in a significant 3 % reduction in serum LDL, 4 % reduction in serum TAG and a 2 % reduction in total cholesterol concentrations.
This beneficial effect seemed stronger in individuals with a higher risk of CHD (hypercholesterolaemic, obese and diabetic subjects). It also appears that consumption of soya foods, based on the whole soya bean, is more effective in lowering serum cholesterol than intake of soya supplements. No effect of isoflavones was observed on serum lipids.
Tokede OA, Onabanjo TA, Yansane A, Gaziano JM, Djousse L. Soya products and serum lipids: a meta-analysis of randomised controlled trials. Br J Nutr 2015;1-13.