Eating animal foods containing saturated fat is linked to High cholesterol levels and Heart disease. Significant amounts of animal-based saturated fat are found in beef, pork, veal, poultry (particularly in poultry skins and dark meat), cheese, butter, ice cream, and all other forms of dairy products not labeled “fat free.” Avoiding consumption of these foods reduces cholesterol and has been reported to reverse even existing Heart disease.
Unlike other dairy foods, skimmed milk, nonfat yogurt, and nonfat cheese are essentially fat-free. Dairy products labeled “low fat” are not particularly low in fat. A full 25% of calories in 2% milk come from fat. (The “2%” refers to the fraction of volume filled by fat, not the more important percentage of calories coming from fat.)
In addition to large amounts of saturated fat from animal-based foods, Americans eat small amounts of saturated fat from coconut and palm oils. Palm oil has been reported to elevate cholesterol.
Research regarding coconut oil is mixed, with some trials finding no link to Heart disease, while other research reports that coconut oil elevates cholesterol levels.
Despite the links between saturated fat intake and serum cholesterol levels, not every person responds to appropriate dietary changes with a drop in cholesterol. A subgroup of people with elevated cholesterol who have what researchers call “large LDL particles” has been reported to have no response even to dramatic reductions in dietary fat. (LDL is the “bad” cholesterol most associated with an increased risk of Heart disease.) This phenomenon is not understood. People who significantly reduce intake of animal fats for several months but do not see significant a reduction in cholesterol levels should discuss other approaches to lowering cholesterol with a doctor.
Yogurt, acidophilus milk, and kefir are fermented milk products that have been reported to lower cholesterol in most, but not all, double-blind and other controlled research. Until more is known, it makes sense for people with elevated cholesterol who consume these foods, to select nonfat varieties.
Eating fish has been reported to increase HDL cholesterol and is linked to a reduced risk of Heart disease in most, but not all, studies. Fish contains very little saturated fat, and fish oil contains EPA and DHA, omega-3 fatty acids that appear to protect against Heart disease.
Vegetarians have lower cholesterol and less Heart disease than meat eaters, in part because they avoid animal fat. Vegans (people who eat no meat, dairy, or eggs) have the lowest cholesterol levels, and switching from a standard diet to a vegan diet, along with other lifestyle changes, has been reported to reverse Heart disease in controlled research.
Most dietary cholesterol comes from egg yolks. Eating eggs has increased serum cholesterol in most studies. However, eating eggs does not increase serum cholesterol as much as eating foods high in saturated fat, and eating eggs may not increase serum cholesterol at all if the overall diet is low in fat.
Egg consumption does not appear to be totally safe, however, even for people consuming a low-fat diet. When cholesterol from eggs is cooked or exposed to air, it oxidizes. Oxidized cholesterol is linked to increased risk of Heart disease. Eating eggs also makes LDL cholesterol more susceptible to damage, a change linked to Heart disease.
Whether or not egg eaters are more likely to die from Heart disease is a matter of controversy. In one preliminary study, egg eaters had a higher death rate from Heart disease, even when serum cholesterol levels were not elevated. However, another preliminary study found no evidence of an overall significant association between egg consumption, and risk of Heart disease or Stroke, except in people with Diabetes. Until more is known, limiting egg consumption may be a good idea, particularly for people with existing Heart disease or Diabetes.
While coconut oil is high in saturated fat, some evidence suggests it does not cause unhealthy changes in blood cholesterol levels compared with other saturated fats. In a controlled study of people with High cholesterol, coconut oil resulted in higher total and LDL cholesterol levels compared with safflower oil (a polyunsaturated oil), but lower levels compared with butter, while HDL levels were similar for all three diets. Another controlled study compared coconut oil with canola oil, and found that coconut oil raised total and LDL cholesterol in people with High cholesterol who were not taking cholesterol-lowering drugs, but did not affect these levels in people who were taking these drugs. HDL levels were not reported in this study.
Soluble fiber from beans, oats, psyllium seed, glucomannan, and fruit pectin has lowered cholesterol levels in most trials. Doctors often recommend that people with elevated cholesterol eat more of these high-soluble fiber foods. However, even grain fiber (which contains insoluble fiber and does not lower cholesterol) has been linked to protection against Heart disease, though the reason for the protection remains unclear. It makes sense for people wishing to lower their cholesterol levels and reduce the risk of Heart disease to consume more fiber of all types. Some trials have used 20 grams of additional fiber per day for several months to successfully lower cholesterol.
Oat bran is rich in a soluble fiber called beta-glucan. In 1997, the U.S. Food and Drug Administration passed a unique ruling that allowed oat bran to be registered as the first cholesterol-reducing food at an amount providing 3 grams of beta-glucan per day, although some evidence suggests this level may not be high enough to make a significant difference. Several double-blind and other controlled trials have shown that oat bran and oat milk supplementation may significantly lower cholesterol levels in people with elevated cholesterol, but only weakly lowers them in people with healthy cholesterol levels.
Flaxseed, another good source of soluble fiber, has been reported to lower total and LDL cholesterol in preliminary studies. A double-blind trial found that while both flaxseed and sunflower seed lowered total cholesterol, only flaxseed significantly lowered LDL. Amounts of flaxseed used in these trials typically range from 30-50 grams per day. A controlled trial found that partially defatted flaxseed, containing 20 grams of fiber per day, significantly lowered LDL cholesterol, suggesting that at least one of the cholesterol-lowering components in flaxseed is likely to be the fiber in this product, as opposed to the oil removed from it. Controlled trials of flaxseed oil alone have shown inconsistent effects on blood cholesterol.
Doctors and researchers are interested in alpha-linolenic acid (ALA)-the special omega-3 fatty acid found in large amounts in flaxseeds and flaxseed oil. ALA is a precursor to EPA, a fatty acid from fish oil that is believed to protect against Heart disease. To a limited extent, ALA converts to EPA within the body. However, unlike EPA, ALA does not lower triglyceride levels (a risk factor for Heart disease). Preliminary research on the effects of ALA from flaxseed has produced conflicting results.
In 1994, researchers conducted a study in people with a history of Heart disease, using what they called the “Mediterranean” diet. The diet was significantly different from what people from Mediterranean countries actually eat, in that it contained little olive oil. Instead, the diet included a special margarine high in ALA. Those people assigned to the “Mediterranean” diet had a remarkable 70% reduced risk of dying from Heart disease compared with the control group during the first 27 months. Similar results were also confirmed after almost four years. Although cholesterol levels fell only modestly in the “Mediterranean” diet group, the positive results suggest that people with elevated cholesterol attempting to reduce the risk of Heart disease should consider such a diet. The diet was high in beans and peas, fish, fruit, vegetables, bread, and cereals; and low in meat, dairy fat, and eggs. Although the authors believe that the high ALA content of the diet was partially responsible for the surprising outcome, other aspects of the diet may have been partly or even totally responsible for decreased death rates. Therefore, the success of the “Mediterranean” diet does not prove that ALA protects against Heart disease.
Tofu, tempeh, miso, and some protein powders in health food stores, are derived from soybeans. In 1995, an analysis of many trials proved that soy reduces both total and LDL cholesterol. Since then, other double-blind and other controlled trials have confirmed these findings. Trials showing statistically significant reductions in cholesterol have generally used more than 30 grams per day of soy protein. However, if soy replaces animal protein in the diet, as little as 20 grams per day has been shown to significantly reduce both total and LDL cholesterol. Isoflavones found in soy beans appear to be key cholesterol-lowering ingredients of the bean, but animal research suggests other components of soy are also important.
Eating sugar has been reported to reduce protective HDL cholesterol and increases other risk factors linked to Heart disease. However, higher sugar intake has been associated with only slightly higher risks of Heart disease in most reports. Although the exact relationship between sugar and Heart disease remains somewhat unclear, many doctors recommend that people with High cholesterol reduce their sugar intake.
Drinking boiled or French press coffee increases cholesterol levels. Modern paper coffee filters trap the offending chemicals and keep them from entering the cup. Therefore, drinking paper-filtered coffee does not increase cholesterol levels. Espresso coffee has amounts of the offending chemicals midway between those of other unfiltered coffees and paper-filtered coffee, but there is little research investigating the effect of espresso on cholesterol levels, and studies to date have produced conflicting results. The effects of decaffeinated coffee on cholesterol levels remain in debate.
Moderate drinking (one to two drinks per day) increases protective HDL cholesterol. This effect happens equally with different kinds of alcohol-containing beverages. Alcohol also acts as a blood thinner, an effect that should lower Heart disease. However, alcohol consumption may cause liver disease (e.g., cirrhosis), cancer, high blood pressure, alcoholism, and, at high intake, an increased risk of Heart disease. As a result, some doctors never recommend alcohol, even for people with High cholesterol. Nevertheless, those who have one to two drinks per day appear to live longer and are clearly less likely to have Heart disease. Therefore, some people at very high risk of Heart disease-those who are not alcoholics, who have healthy livers and normal blood pressure, and who are not at high risk for cancer, particularly breast cancer-are likely to receive more benefit than harm, from light drinking.
Olive oil lowers LDL cholesterol, especially when the olive oil replaces saturated fat in the diet. People from countries that use significant amounts of olive oil appear to be at low risk for Heart disease. A double-blind trial showed that a diet high in monounsaturated fatty acids from olive oil, lowers cardiovascular disease risk by 25%, as compared with a 12% decrease from a low-fat (25% fat) diet. The trial also found that low-fat diets decrease HDL cholesterol by 4%, which is undesirable, since HDL cholesterol is protective against Heart disease. Diets high in monounsaturated fatty acids from olive oil do not adversely affect HDL levels. Although olive oil is clearly safe for people with elevated cholesterol, it is, like any fat or oil, high in calories, so people who are overweight should limit its use.
Trans fatty acids and margarine
Trans fatty acids (TFAs) are found in many processed foods containing partially hydrogenated oils. The highest levels occur in margarine. Margarine consumption is linked to increased risk of unfavorable changes in cholesterol levels and Heart disease. Margarine and other processed foods containing partially hydrogenated oils should be avoided.
However, special therapeutic margarines are now available that contain substances, called phytostanols, that block the absorption of cholesterol. The FDA has approved some of these margarines as legitimate therapeutic agents for lowering blood cholesterol levels. The best-known of these products is Benecol™. The cholesterol-lowering effect of these margarines has been demonstrated in numerous double-blind and other controlled trials.
Garlic is available as a food, as a spice in powder form, and as a supplement. Eating garlic has helped to lower cholesterol in some research, though several double-blind trials have not found garlic supplements to be thusly effective. Although some of the negative reports have been criticized, the relationship between garlic and cholesterol lowering remains unproven. However, garlic is known to act as a blood thinner and may reduce other risk factors for Heart disease. For these reasons, some doctors recommend eating garlic as food, taking 900 mg of garlic powder from capsules, or using a tincture of 2 to 4 ml, taken three times daily.
Preliminary research consistently shows that people who eat nuts frequently have a dramatically reduced risk of Heart disease. This apparent beneficial effect is at least partially explained by preliminary and controlled research demonstrating that nut consumption lowers cholesterol levels. Of nuts commonly consumed, almonds and walnuts may be most effective at lowering cholesterol. Macadamia nuts have been less beneficial in most studies, although one controlled trial found a cholesterol-lowering effect from macadamia nuts. Hazelnuts and pistachio nuts have also been reported to help lower cholesterol.
Nuts contain many factors that could be responsible for protection against Heart disease, including fiber, vitamin E, alpha-linolenic acid (found primarily in walnuts), oleic acid, magnesium, potassium, and arginine. Therefore, exactly how nuts lower cholesterol or lower the risk of Heart disease remains somewhat unclear. Some doctors even believe that nuts may not be directly protective; rather, people busy eating nuts will not simultaneously be eating eggs, dairy, or trans fatty acids from margarine and processed food, the avoidance of which would reduce cholesterol levels and the risk of Heart disease. Nonetheless, the remarkable consistency of research outcomes strongly suggests that nuts do help protect against Heart disease. Although nuts are loaded with calories, a preliminary trial surprisingly reported that adding hundreds of calories per day from nuts for six months did not increase body weight in humans -an outcome supported by other reports. Even when increasing nut consumption has led to weight gain, the amount of added weight has been remarkably less than would be expected, given the number of calories added to the diet. Given the number of calories per ounce of nuts, scientists do not understand why moderate nut consumption apparently has so little effect on body weight.
Number and size of meals
When people eat a number of small meals, serum cholesterol levels fall compared with the effect of eating the same food in three big meals. People with elevated cholesterol levels should probably avoid very large meals and eat more frequent, smaller meals.
Revision date: June 20, 2011
Last revised: by Jorge P. Ribeiro, MD