A recent article in the BJSM suggests that there is no association between saturated fat consumption and Coronary Heart Disease (CHD) mortality. Lifestyle interventions including a healthy diet, regular exercise and reduced stress are more effective in reducing the risk of CHD and all-cause mortality than just monitoring lipid profiles.
A recent article published in the British Journal of Sports Medicine by Aseem Malhotra and colleagues draws our attention to coronary artery disease pathogenesis and recommends the existing theoretical model of saturated fat clogging the arteries be reviewed. As reported by a landmark systematic review and meta-analysis of several studies, in healthy adults there is no association between saturated fat consumption and CHD, ischemic stroke, type-2 diabetes, or CHD/all-cause mortality. Reduced intake of dietary fat, including saturated fat, was not found to have an additional benefit in prevention of cardiovascular or all-cause mortality. Additionally, an angiographic study of postmenopausal women with CHD showed that progression of atherosclerosis was directly proportional to a high carbohydrate and polyunsaturated fat intake and inversely proportional to intake of saturated fat.
Atherosclerosis is a syndrome affecting arterial blood vessels due to a chronic inflammatory response. This is promoted by low-density-lipoproteins (LDL) and inadequate removal of fats and cholesterol by functional high-density-lipoproteins (HDL), resulting in the formation of plaques. Unstable plaques can rupture causing the formation of thrombi that will rapidly slow or stop blood flow, leading to death of the tissue fed by the artery. Preventing the progression of atherosclerosis is important, but it is the atherothrombosis that causes mortality. The results of many randomized controlled trials (RCTs) reveal that the current approach of unclogging the arteries is not effective in the management of CHD. These trials suggest that stenting obstructive stable lesions do not prevent myocardial infarction or reduce mortality.
Dietary RCTs conducted on high-risk patients highlight the benefits of diet in primary and secondary prevention of CHD. Researchers report a significant, 30% reduction in adverse cardiovascular events in patients put on energy-unrestricted Mediterranean diet (41% fat), supplemented with at least four tablespoons of olive oil or a handful of nuts, compared with patients who were only advised to follow a low-fat (37% fat) diet. In addition, the Lyon Heart study conducted to evaluate the effects of Mediterranean diet on secondary prevention of CHD concluded that it is the alpha linoleic acid, polyphenols and omega-3 fatty acids present in nuts, extra virgin olive oil, vegetables and oily fish that rapidly reduce inflammation and coronary thrombosis.
Based on these findings, the association of LDL cholesterol with coronary thrombosis needs to be reevaluated. Unpublished data from the Sydney Diet Heart Study and the Minnesota coronary experiment were reanalyzed to reveal that replacing saturated fat with linoleic acid containing vegetable oils increased the risk of mortality despite significant reductions in LDL and total cholesterol (TC). Thus, a high TC to HDL ratio, not LDL, is proven to be a better indicator of cardiovascular risk. Furthermore, high TC to HDL ratio is also a marker for insulin resistance (chronically elevated serum insulin), which is a risk factor for CHD.
Lifestyle interventions, including dietary changes and regular exercise are effective in lowering the TC to HDL ratio. Regular brisk walking or moderate activity also help reverse insulin resistance. Chronic stress is another risk factor for CHD and lifestyle interventions to reduce environmental stress also help reduce cardiovascular risk.
In conclusion, monitoring lipid profiles and just reducing your saturated fat intake is not the best approach to preventing and treating coronary artery disease. Adopting a complete lifestyle approach of a healthful diet, regular exercise, and reduced stress is more effective in reducing cardiovascular risk and mortality, as well as improving quality of life.
Written By: Preeti Paul, MS Biochemistry