by Gary Pepper M.D. | Aug 22, 2008 | general health & nutrition
For years the press has reported that Omega-3 fatty acids from fish and flax oil are beneficial to the cardiovascular system. However, few people realize the positive effect that Omega-9 fats have on cardiovascular health. In this month of “matters of the heart”, we shall explore such benefits.
Omega-9 fats are the monounsaturated fatty acids.
Back in 1992, the American Journal of Clinical Nutrition released a study comparing long term monounsaturated fatty acid diets with polyunsaturated fatty acid diets on lipoprotein levels of healthy men and women. Researchers concluded that polyunsaturated fats reduced LDL and HDL levels, while monounsaturated fats reduced LDL, and increased HDL levels. This is an important fact to understand. High density lipoproteins (HDL) are protective in that they transport cholesterol back to the liver from peripheral cells, and the circulation, for breakdown and excretion. In this same year, another study called the Jerusalem Nutrition Study examined the effects of a diet high in monounsaturated fats as compared with a diet high in carbohydrates. Total cholesterol and LDL levels decreased significantly on the monounsaturated fat diet, whereas on the high carbohydrate diet no significant change in cholesterol concentrations occurred. In addition, the monounsaturated fat diet seemed to protect LDL from damage by free radicals, which sparked future research, as I will address further in this article.
Another protective factor called apolipoprotein A-1, the major constituent of HDL, was shown to be increased by monounsaturated fatty acids. According to a study in the American Journal of Clinical Nutrition, a diet rich in monounsaturated fatty acids may be more advantageous than a diet rich in polyunsaturated fatty acids because it does not lower apolipoprotein A-1 concentrations.
In the December 1999 American Journal of Clinical Nutrition, Clinical Nutritionists compared the effect of four diet patterns on the cardiovascular disease (CVD) risk profile with a standard American diet. The four diets were the American Heart Association, National Cholesterol Education Program Step II diet, and 3 high monounsaturated fatty acid diets (the first with olive oil, the second with peanut oil, and the third with peanuts and peanut butter). The researchers concluded that the high monounsaturated fatty acid diets lowered total cholesterol and LDL by levels comparable to that of the American Heart Association/ Step II diet. However, in the monounsaturated fatty acid diets, triglycerides decreased and HDL levels did not decrease at all. On the other hand, triglycerides increased and HDL decreased on the American Heart Association/Step II diet. The three monounsaturated fatty acid diets decreased CVD risk by a higher percentage than the American Heart Association/Step II diet. Based on this data, researchers suggested a high monounsaturated fatty acid, cholesterol lowering diet, may be preferable to a low-fat diet due to more favorable effects on the CVD risk profile.
Another study tried to compare the effects of high monounsaturated fat diets with high carbohydrate diets in adults at high risk for type 2 diabetes. Researchers reported in the European Journal of Clinical Nutrition that HDL levels increased on the monounsaturated fat diets, and total cholesterol decreased even though the diet contained 40% of its calories from fat, with 25% from monounsaturated sources.
Researchers in Italy, compared a high carbohydrate, low fat diet, with a reduced carbohydrate, high monounsaturated fat diet on CVD risk factors in mildly obese women. The results in a 1999 issue of the Journal of Internal Medicine illustrated that HDL increased significantly in the high monounsaturated fat diet group, whereas a decreased level was observed in the high carbohydrate group.
At the beginning of the study, the obese women had higher very low density lipoprotein (VLDL) and LDL cholesterol, and lower HDL cholesterol levels that persisted in the high carbohydrate diet group, but a significant decrease in LDL levels, and an increase in HDL cholesterol occurred in the high monounsaturated fat diet group. Lastly, a major constituent of HDL called apolipoprotein A-1, which is believed to be protective against CVD increased in the high monounsaturated fat diet group, and decreased in the high carbohydrate diet group.
In an interesting study in the April 1999 Free Radical Research, monounsaturated fat (specifically olive oil), was compared with polyunsaturated fat in rate or existence of free radical damage to LDL cholesterol. The theory is that LDL becomes more involved in the process of atherosclerosis after undergoing oxidative damage, thus increasing CVD risk. The researchers concluded that monounsaturated fat helped LDL become more resistant to free radical damage. Such evidence coincides with that of the aforementioned Jerusalem Nutrition Study’s reporting of decreased free radical damage of LDL cholesterol due to dietary increase of monounsaturated fat.
In 1998, the European Journal of Clinical Nutrition printed another study testing the potential rate of LDL damage by free radicals in patients with impaired glucose tolerance, on either a high monounsaturated fat, or polyunsaturated fat diet. The results revealed that in subjects with impaired glucose tolerance, a polyunsaturated rich diet with a moderate amount of fat tended to increase the susceptibility of LDL to free radical damage as compared to a high monounsaturated fat diet, which seemed to protect LDL from such damage.
Does this mean we should all increase our fat intake? Not exactly. In response to this mounting evidence, it might be wise to replace saturated fats, and some carbohydrate with monounsaturated fats in the diet, which is what I do when designing personal nutritional profiles. Such a plan may be a more effective option for improving cardiovascular function, lipid profiles, and glycemic control.
Foods high in monounsaturated fats include avocados, nuts and nut butters, seeds and seed butters (such as tahini), olives, olive oil and canola oil.