Can vitamins lower cholesterol?

What exactly are antioxidants? Antioxidants include some vitamins and minerals, but to appreciate the value of antioxidants, you first need to understand the potential dangers of free radicals, a form of oxygen that has been chemically modified into a highly unstable substance.

Free radicals are unstable because they are missing electrons, which must be replaced. So they seek out other compounds in the body and steal electrons to restore stability. If the compound giving up its electrons is the fat and protein in an LDL-cholesterol molecule, the result is the formation of fatty lesions in the walls of the blood vessels -- the hallmark of atherosclerosis.

Although the body has a means of handling a normal burden of free radicals, many of the forces that cause free radicals to form cannot be stopped. For instance, they form in the normal course of the day, just by our breathing in oxygen. (Obviously, it's impossible to avoid this type of free radical because we have to breathe.)

Yet the production of free radicals is not always a bad thing. They are part of the immune system and help fight off infection. (During cancer treatment, the free radicals produced help to destroy cancer cells.) Antioxidants are the armament the body uses for protection against damage from free radicals. It is when the production of free radicals overwhelms the body's protective system of antioxidants that disease-producing damage results.

The heart and the blood vessels, like the lungs, are especially vulnerable to the effects of oxygen because their exposure to this element is so great. The blood is the route of transport for oxygen throughout the body. The blood is also the route of transport for many of the substances that can act on oxygen to produce free radicals.

Cholesterol is carried through the blood, packaged in LDL particles; LDL is responsible for depositing cholesterol in the walls of the arteries. These deposits form the fatty plaques that eventually narrow the arteries, possibly leading to a heart attack. Scientists now know that before LDL cholesterol can have this effect, it first has to be modified by a free radical to form an oxidized LDL.

In other words, the free radical substances produced in the blood from oxygen by any one of a number of causes -- like chemicals from cigarette smoke or environmental pollution -- can set off a chain of events that generates oxidized LDL cholesterol and ultimately can lead to heart disease.

The body benefits from a variety of different antioxidants. Vitamin C, vitamin E, and beta-carotene (a compound related to vitamin A) are the vitamin antioxidants. Oranges, grapefruit, strawberries, green peppers, broccoli, and tomatoes are rich in vitamin C. Carrots, apricots, squash, spinach, and other green leafy or yellow-orange fruits and vegetables are rich sources of beta-carotene. Vitamin E is found in dark-green leafy vegetables, nuts, and vegetable oils.

The mineral selenium is a component of antioxidant enzymes, so it acts as an antioxidant when combined with these special proteins. A number of natural compounds found in plant sources also have antioxidant activity, but these are neither vitamins nor minerals. Flavonoids, which are found in apples, tea, and onions, are an example. Red wine is also believed to contain a flavonoid antioxidant that may partly explain the protection from high rates of heart disease attributed to people in some Mediterranean countries.

Antioxidants protect against damage from free radicals either by preventing them from forming altogether or by destroying them once they have formed. Generally, vitamin antioxidants act as scavengers that intercept free radicals before they can interact with LDL cholesterol or other important cell compounds.

Additionally, there is growing evidence that inflammation in the arteries can cause plaque to rupture, triggering the formation of clots. It is a clot that may eventually plug an artery that has been narrowed by fatty plaques, thereby cutting off the supply of oxygen to a portion of the heart -- which may bring on a heart attack. Since free radicals can trigger an inflammatory response, it is possible that antioxidants may help control inflammation.

One particular concern with taking antioxidant supplements is their effect on cancer. Large clinical trials in the 1990s, mostly on beta-carotene, have shown inconsistent results. In 1994, a well-publicized study on Finnish male smokers found a higher incidence of lung cancer in men who took beta-carotene supplements, but in 1996, another large study of mostly nonsmoking doctors found no change in cancer rates among those who took beta-carotene supplements. A study on the effect of antioxidant supplements on the risk of prostate cancer is currently underway. Overall, it appears that the role of antioxidant supplements in cancer prevention is still unclear.

The rest of this article will give you the latest scientifically based information on the roles that certain vitamins, minerals, and antioxidants may play in modifying blood cholesterol and lowering the risk of heart disease. We'll start out with the role that the B vitamins might play for your heart, explained on the next page.

A group of B vitamins -- folic acid, vitamin B12, and vitamin B6 -- may have a role in heart health. In a complex series of reactions, these vitamins are responsible for regulating the blood levels of an amino acid called homocysteine. An elevated blood level of homocysteine is one of the risk factors for heart disease.

Evidence suggests, although it's not proven, that homocysteine oxidizes LDL, thereby promoting atherosclerosis. Unfortunately, two large clinical trials of men and women with heart disease have not shown any benefit of folate, B12, and B6 supplements in lowering homocysteine, indicating that homocysteine may be a marker of coronary heart disease, not a target of treatment.

Green leafy vegetables, such as spinach and kale, as well as brussell sprouts, asparagus, beans, orange juice, and fortified cereals are good sources of folate. Since 1998, the United States government has required that folic acid be added to refined grain products, such as white bread, pasta, and rice. However, these refined grains should not be substituted for whole grains in the diet.

Vitamin B12 can be found in lean red meat, fish, shellfish, and fortified cereals. Chicken, fish, whole-wheat bread, beans, and fortified cereals contain vitamin B6.

Niacin is another B vitamin. In large doses, nicotinic acid, a form of niacin, lowers total cholesterol, LDL cholesterol, and triglyceride levels and raises HDL levels.

Evidence is also inconclusive on the role that carotenoids, which provide Vitamin A, play in cholesterol. Learn about carotenoids on the next page.

Carotenoids such as beta-carotene are natural pigments synthesized by plants that are responsible for the yellow, orange, red, and dark-green colors of various fruits and vegetables. About 50 carotenoids -- many of which the body can convert into retinol, an active form of vitamin A -- are consumed in the human diet, although people most often consume only 12.

Carrots, sweet potatoes, cantaloupe, and apricots are sources of alpha- and beta-carotene; tomatoes, watermelon, and pink grapefruit contain lycopene; mango, peaches, squash, and oranges provide beta-cryptoxanthin, lutein, zeaxanthin, and alpha- and beta-carotene; and greens such as spinach, kale, and broccoli contain lutein, zeaxanthin, and alpha- and beta-carotene.

Carotenoids act as antioxidants, protecting cells from damage by free radicals, and in clinical trials, beta-carotene is the most researched of the antioxidant supplements. The evidence supporting the link between beta-carotene and a reduced risk of heart disease or heart attack is inconclusive at best.

In the Women's Health Study and the all-male Physicians' Health Study, 50 mg of beta-carotene supplementation every other day had no effect on the incidence of heart attack, other cardiovascular events, or death. In another study, male smokers who took 20 mg of beta-carotene supplements a day for five to eight years showed an 8 percent increase in the rate of death due to heart disease and lung cancer, and in a follow-up, those participants also seemed to be at a higher-risk for a first-time nonfatal heart attack.

Evidence suggests that carotenoids may protect LDL cholesterol from the damage caused by oxidation, but the results are inconclusive. Also, some studies have found that at high concentrations, carotenoids may actually have a damaging effect on cells. There is no good information supporting beta-carotene supplements to reduce the risk of heart attack.

Vitamin C has shown a little promise in heart studies, but the evidence is still inconclusive. Learn about Vitamin C research on the next page.

Well known for its effects on diminishing the symptoms of the common cold, vitamin C -- which is a strong antioxidant and can be found in citrus fruits, strawberries, green peppers, tomatoes, and potatoes -- has received some attention for its possible role in reducing the risk of heart disease. Much of the vitamin C research in humans has been based on cohort studies, which follow large groups of people with common characteristics over a long period of time.

In three of five cohort studies, it was found that vitamin C supplementation had no effect on preventing heart disease. However, in a review of nine other cohort studies, those who took over 700 mg of supplemental vitamin C a day were found to have a 24 percent lower risk of heart disease than those who did not take supplements. At this time, the evidence to support taking supplemental vitamin C to prevent heart disease is inconclusive.

There is also evidence suggesting calcium may help lower cholesterol. Find out about this link on the next page.

You've probably heard that calcium is good for strong bones, but some evidence suggests that calcium helps lower cholesterol levels as well. In addition, calcium may help reduce blood pressure, especially when it's part of a diet that contains plenty of fruits and vegetables.

It's possible that calcium may have to interact with other minerals, such as potassium and magnesium, before it has its full impact. However, high levels of sodium may interfere with calcium's beneficial effects.

Low-fat or nonfat dairy products, such as nonfat milk and yogurt, are high in calcium and contain little or no saturated fat. Although cheese is a good source of calcium, it is high in saturated fat, cholesterol, and sodium; light or part-skim cheese cuts down on fat and calories. Calcium-fortified orange juice, dried beans and peas, and dark-green leafy vegetables are good nondairy sources of calcium.

The mineral chromium may lower heart disease, but the evidence for lowering cholesterol per se is contradictory. Learn about chromium on the next page.

Chromium, a mineral, has a role in regulating blood-sugar levels. It can improve insulin sensitivity, which may lower the risk of diabetes and heart disease.

Research suggests that chromium supplements may have an effect on blood-lipid levels, but the results are contradictory. In some studies, chromium supplements ranging from 150 to 1,000 micrograms (mcg) a day lowered total cholesterol, LDL cholesterol, and triglycerides -- and increased apolipoprotein A, a component of HDL cholesterol -- in people with heart disease or elevated blood cholesterol. But other studies found no positive effects on blood-lipid levels.

Chromium is found in small amounts in a variety of foods, including whole grains and lean meats. Recommended adequate intake is 25 mcg for adults under age 50, and 20 mcg for adults age 50 and older. It is estimated that most adults get at least that amount in their diets.

Research is also unclear on whether Vitamin E is effective against heart disease. The next page goes into detail on this research.

Vitamin E has been cited as offering protection against heart disease, yet scientific evidence supporting its beneficial effects is conflicting. This may be, in part, because we don't clearly understand vitamin E's role in the body.

We know that vitamin E is carried through the blood with LDL cholesterol. Because of its close proximity to LDL, vitamin E has been expected to protect LDL from oxidation by free radicals. But that may not be exactly so. It may be that a balance between vitamin E and other antioxidants is needed in order to get antioxidant protection, or perhaps vitamin E is not as effective as was once thought.

In an analysis of seven trials of more than 81,000 people who had or were at high risk for heart disease, vitamin E supplements ranging from 50 to 800 International Units (IU) did not lower the risk of cardiovascular death.

In the Women's Health Study, nearly 20,000 healthy women who took 600 IU of natural-source supplemental vitamin E every other day for ten years had no reduction in risk for major cardiovascular events. The 24 percent reduction in sudden cardiovascular death among women who took vitamin E supplements may have been due to chance.

Ultimately, these data did not support recommending vitamin E supplements for preventing cardiovascular disease in healthy women.

Out of seven clinical trials, only the Cambridge Heart Antioxidant Study found that vitamin E supplements provided beneficial effects in preventing cardiac events in people with heart disease, and that study appeared to have some design flaws that may have influenced the results.

In fact, in 2005, a clinical trial known as the Heart Out comes Prevention Evaluation -- The Ongoing Outcomes (HOPE-2) found that 400 IU of vitamin E a day might actually increase the risk of heart failure. This example shows that when it comes to taking supplements, more is not always better; in fact, it may cause harm.

It's interesting to note that many of the clinical trials were conducted on people with established coronary heart disease or who were already at high risk; it's possible that vitamin E may be more helpful in preventing heart disease from occurring than in treating people who already have heart disease. More research and analysis will help find the answers to the vitamin E puzzle. Until then, there is no good evidence supporting the use of large dose vitamin E (400 IU or more) to reduce the risk of heart attack.

Selenium, on the other hand, is known to be an antioxident. Learn about this mineral on the next page.

Selenium is a trace mineral required by the body in small amounts. It combines with proteins to make selenoproteins, which are important antioxidant enzymes that may help protect cells from damage by free radicals.

It is thought that selenium may help limit the oxidation of LDL cholesterol, helping to protect against coronary heart disease. Some population studies have linked the antioxidant properties of selenium to lower risk of cardiovascular disease, but the findings are controversial. Selenium deficiency has been implicated in heart disease and other conditions that involve oxidative stress and inflammation, but the evidence is limited.

The selenium content in food depends on the amount of selenium in the soil. Plants can only take up selenium to the extent that it is concentrated in a particular soil. So, if plants are grown in low-selenium soil, they will not provide good dietary sources of selenium.

In the United States, our food supply comes from various regions that are both low and high in selenium. But in some parts of China, for example, the soil is very low in selenium, which may lead to a selenium deficiency there. An often-fatal illness, Keshan's disease (in which the heart muscle is damaged), is frequent among residents living in the low-selenium regions of China.

Some of the richest sources of selenium are fish and whole grains grown in selenium-rich soil. Brazil nuts are especially high in selenium but should be limited to a couple of nuts at a time and eaten only occasionally -- selenium has a very high toxicity if too much is consumed.

Caution must be exercised when taking a selenium supplement, particularly when it is a selenium salt, such as sodium selenite. Organic forms of selenium, such as selenomethionine or selenocysteine, may be less toxic. Currently, there is insufficient evidence to recommend selenium supplements to prevent heart disease.

The jury is still out on whether vitamins and minerals can lower cholesterol. Using the information in this article, you'll know what to expect -- and what not to expect -- from the vitamins in your diet.

To learn more about vitamins and tips for improving your health, check out the links on the next page.