The Harvard researchers, led by Dariush Mozaffarian from Harvard Medical School, analysed eight trials, which provided data on 13,614 participants and 1,042 coronary heart disease events.
For every 5 per cent increase in polyunsaturated fat consumption, the researchers reported a 10 per cent reduction in the risk of coronary heart disease (CHD), according to a systematic review and meta-analysis published in PLoS Medicine.
Contradicting the consensus
The study supports the widely supported theory that saturated fats are detrimental to heart health. The UK’s Food Standards Agency (FSA) has previously stated estimated that if people cut their saturated fat intake to government recommendations it could prevent up to 3,500 premature deaths a year, saving the UK economy more than £1bn a year in related costs.
Such estimates have led to public awareness campaigns in the UK, including a £3.5m advertising campaign to encourage consumers to reduce their intake of saturated fat and change the way they shop and eat.
Last month, however, a meta-analysis funded by the US National Dairy Council, Unilever, and the National Institutes of Health, reported contradictory evidence. Data from almost 350,000 subjects obtained from 21 studies indicated that dietary intakes of saturated fat are not associated with increases in the risk of either coronary heart disease (CHD) or cardiovascular disease (CVD), US researchers reported in the American Journal of Clinical Nutrition (March 2010, Volume 91, Pages 535 – 546).
The new study drives this forward by not only linking saturated fats to heart disease, but also that the choice of substituted fats is important.
“The specific replacement nutrient for saturated fat may be very important,” said lead author Mozaffarian. “Our findings suggest that polyunsaturated fats would be a preferred replacement for saturated fats for better heart health.”
Implications for dietary guidelines and reformulation
The study may have implications for recommended daily intakes of omega-3 fatty acids, said the researchers, with current guidelines from the Institute of Medicine (IoM) stating a range between 5 and 10 per cent from polyunsaturated fats.
“The results from this study suggest that polyunsaturated fats from vegetable oils may be an optimal replacement for saturated fats, an important finding for dietary guidelines and for when food manufacturers and restaurants are making decisions on how to reduce saturated fat in their products,” wrote Mozaffarian and his co-workers.
“The findings also suggest that an upper limit of 10 per cent energy consumption from polyunsaturated fats may be too low, as the participants in these trials who reduced their risk were consuming about 15 per cent energy from polyunsaturated fats,” they concluded.
The study was supported by the National Heart, Lung, and Blood Institute, NIH and a Searle Scholar Award from the Searle Funds at the Chicago Community Trust.
Source: PLoS Medicine
March 23, 2010, Volume 7, Issue 3, e1000252
“Effects on Coronary Heart Disease of Increasing Polyunsaturated Fat in Place of Saturated Fat: A Systematic Review and Meta-Analysis of Randomized Controlled Trials”
Authors: D. Mozaffarian, R. Micha, S. Wallace
The full article is available here .