Cholesterol is a class of lipid/fat. Too much cholesterol in the blood, particularly low-density lipoprotein or "‘bad" cholesterol, contributes to plaque formation that clogs arteries, a risk factor for heart disease. On the other hand, elevated levels of high-density lipoprotein or "good' cholesterol is protective against heart disease. HDL travels throughout the bloodstream, collecting cholesterol and carrying it back to the liver for breakdown and disposal. Causes of low levels of HDL cholesterol include genetics, a lack of exercise and dietary factors.
Lipid disorders are very significant, independent risk factors for the development of coronary heart disease. Prevention studies such as the Coronary Primary Prevention Trial and the Helsinki Heart Study have shown that lowering LDL and raising HDL cholesterol levels significantly decreases the risk for heart disease. According to the National Cholesterol Education Program guidelines, HDL cholesterol levels of less than 35 mg/dl are considered too low. The ratio of total cholesterol to HDL cholesterol is equally important in determining risk for heart disease and should be less than 5. Other institutions recommend higher HDL levels for cardiovascular benefits.
The genetic control of HDL level is complex but exists. A genetic disposition toward low HDL cholesterol is a risk factor for cardiovascular disease that can't be controlled. Thus, lifestyle modification is more important for those predisposed to low HDL cholesterol levels. According to an article published by Current Opinion in Cardiology, as many as 20 percent of people with low HDL cholesterol have a rare gene mutation that interferes with HDL synthesis. Mutations of common variants of the ABCA1 gene may contribute to low HDL levels in the general population.
Not Enough Exercise
Exercise significantly improves cholesterol levels and is particularly beneficial for raising HDL cholesterol. A recent study published by the Research Quarterly for Exercise and Sport investigated the effects of regular exercise on cholesterol levels (contributing to heart disease) of 20 sedentary men over 20 consecutive years. The ages ranged from 30 to 51. Those who participated in a formal exercise program for 45 minutes daily for 3 1/2 days a week had an improvement in all blood lipid levels, including an increase in HDL cholesterol levels and a lower ratio of total to HDL cholesterol. Moderate physical activity (as little as 30 minutes, three days a week of aerobic activity) is enough to increase HDL levels significantly.
Too Little Dietary Omega-3 Fatty Acids
There are two types of omega-3 fatty acids (an essential fatty acid), docosahexanoic acid and eicosapentaenoic acid. Nuts -- especially walnuts -- and canola, flaxseed, soybean, walnut and wheat germ oils are all rich sources of DHA. EPA is found in fatty, cold-water fish such as salmon, mackerel, sardines, halibut, trout and tuna. Not consuming enough omega-3 fatty acid-rich foods is a contributing factor in low HDL cholesterol levels.
Not Consuming the Right Plant Foods
Certain fruits may increase HDL cholesterol. Fruits with dark red or purple skins are high in a polyphenol compound called resveratrol. Cherries, grapes, apples and berries are particularly high in resveratrol, according to a review in the November--December 2009 issue of "Oxidative Medicine and Cellular Longevity." As stated in the review, resveratrol foods are shown to significantly increase HDL levels.