Evidence doesn't support current guidelines on fat consumption

Dietary guidelines favoring high consumption of polyunsaturated fats and low consumption of saturated fats to reduce coronary risk are not supported by the available evidence, a recent meta-analysis found.

Researchers reviewed 32 observational studies of fatty acids from dietary intake and 17 of fatty acid biomarkers, as well as 27 randomized, controlled trials of fatty acid supplementation. In total, their data included more than 600,000 people in 18 countries. They evaluated associations between fatty acids and coronary disease. Results were published in the March 18 Annals of Internal Medicine.

In the observational trials, the relative risk (RR) for coronary disease between those consuming the most and the least of most types of fatty acid were not significantly different: 1.02 (95% CI, 0.97 to 1.07) for saturated; 0.99 (95% CI, 0.89 to 1.09) for monounsaturated; 0.93 (95% CI, 0.84 to 1.02) for long-chain, omega-3 polyunsaturated; and 1.01 (95% CI, 0.96 to 1.07) for omega-6 polyunsaturated. Higher consumption of trans fatty acids was associated with a RR of 1.16 (95% CI, 1.06 to 1.27).

Studies measuring circulating fatty acids revealed no significant differences in coronary risk and heterogeneity of associations between the fatty acids and coronary disease. Analysis of the randomized trial data revealed no significant differences in risk for coronary disease when supplementation with alpha-linolenic or long-chain, omega-3 polyunsaturated fats were compared to omega-6 polyunsaturated fats.

To explain their findings, the study authors noted that self-reports of fat consumption can be inaccurate but also said that circulating fatty acid levels can be significantly affected by how the body metabolizes the fats consumed. For example, the analysis found positive associations between coronary disease and circulating palmitic and stearic acids (which are only weakly associated with fat consumption) and a negative association with margaric acid (a saturated fat increased by milk and dairy consumption). This finding may suggest that saturated fats from milk or dairy could have less deleterious effects on coronary health than other types.

Overall, the findings are in line with current guidelines on avoidance of trans fats but do not support cardiovascular guidelines encouraging high consumption of polyunsaturated fats and low consumption of saturated fats, the authors concluded. “Nutritional guidelines on fatty acids and cardiovascular guidelines may require reappraisal,” they wrote.