Fighting heart disease: Should you be "pro" or "anti" antioxidants?
Antioxidants are natural substances that exist as vitamins, minerals and other compounds in foods. They are believed to help prevent disease by fighting free radicals, substances that harm the body when left unchecked. Free radicals are formed by normal bodily processes such as breathing, and by environmental contaminants like cigarette smoke. Without adequate amounts of antioxidants, these free radicals travel throughout the body, damaging cells.
Part of this cellular damage leads to one of the major known factors in the development of heart disease, oxidation of cholesterol. Oxidation, meaning the addition of oxygen to low-density lipoproteins (LDL or "bad" cholesterol), contributes to the build up of fatty plaque on artery walls (atherosclerosis), which can eventually slow or block blood flow to the heart.
The potential link between LDL oxidation and antioxidants has led investigators to explore the role of antioxidants and heart disease. Over the years, many studies have been done. However, the designs of some of the studies left their results open to question. For example, some of the studies used too few participants to obtain valid results. Some used doses of vitamin E that were later thought too low. Some had a limited duration of treatment, and others could not determine whether the beneficial results were from the antioxidants or other lifestyle factors.
On the other hand, some of the studies were well designed. Nonetheless, their results differed from one another. Some found benefit in antioxidants. Some didn't. Still others found potential harm from one of the antioxidants, beta carotene.
The media has announced the findings of these conflicting studies with great fanfare. "Take vitamin E to fight heart disease." Or : "Don't take vitamin E ," leaving consumers confused about the best way to support their cardiac health.
Clearing the confusion
Researchers at the Cleveland Clinic decided to clear up the confusion by doing a meta-analysis, an overview study of the best designed, largest studies of antioxidants. A meta-analysis allows investigators to combines the results of many studies, thereby allowing small benefits or harm to be seen that may not have been appreciated in any one study. Their findings were recently published in the prestigious British medical journal The Lancet. Here's what they found.
The researchers analyzed results from seven large randomized trials of vitamin E, alone or in combination with other antioxidants, and eight of beta carotene. The doses of vitamin E ranged from 50-800 international units (IU); for beta carotene, the doses were 15-50 milligrams (mg).
Overall, 81,788 patients were included in the vitamin E portion of the meta-analysis and 138,113 in the beta carotene portion. The CCF researchers looked for the effect of antioxidant vitamins on death rates, either from cardiovascular disease or from any other cause ("all-cause mortality").
The bottom line
Vitamin E did not provide any benefit in lowering mortality compared to control treatments, and it did not significantly decrease the risk of cardiovascular death or stroke ("cerebrovascular accident"). The lack of any beneficial effect was seen consistently regardless of the doses of vitamins used and the diversity of the patient populations. Therefore, the CCF researchers conclude that this study does "not support the routine use of vitamin E."
Beta carotene led to small but statistically significant increase in all-cause mortality and a slight increase in cardiovascular death. The researchers call their findings "especially concerning" because beta carotene doses are commonly included in over-the-counter vitamin supplements and multivitamin supplements that have been advocated for widespread use.
The study says that using vitamin supplements that contain beta carotene should be "actively discouraged" because of the increase in the risk of death. They also recommend discontinuing study of beta carotene supplements because of their risk.
Researchers further stated that they do not support the continued use of vitamin E treatment, and they discourage the inclusion of vitamin E in further studies of patients who are known to be at high-risk of heart disease.
These findings further strengthen the contention that diet supplements are no substitute for good eating habits, exercise, weight loss and smoking cessation as a means of minimizing the risk of heart disease.
Antioxidant foods: A different story
Even though supplements did not prove beneficial in avoiding heart problems, foods that are sources of antioxidants are still recommended. There are benefits to getting vitamins in food that don't necessarily occur in supplement form. For example, foods rich in antioxidants may have nutrients such as flavonoids and lycopenes which are not necessarily included standard oral vitamin supplements. Eating a diet rich in antioxidant-containing foods, such as fruits, vegetables and whole grains, is linked to a reduced risk of cardiovascular (heart and blood vessels) disease.
Good food sources of antioxidants
Sources of vitamin E:
Best: green leafy vegetables, legumes, nuts, papaya, seeds, and whole grains.
Good: brown rice, oatmeal, soybeans, sweet potatoes, watercress, wheat and wheat germ.
Sources of beta carotene
Best sources are dark orange, red and dark green vegetables and fruits.
National and international dietary recommendations are to eat between five and 10 servings of fruit and vegetables daily to ensure adequate intake of disease-fighting antioxidant nutrients.
To reduce your risk of heart disease , it remains important to decrease your risk factors using more proven methods than vitamin supplementation. Some of the best methods include:
- Quit smoking and using tobacco products
- Have your doctor check your lipid profile
- Get treatment, if necessary, to reach a lipid goal of LDL less than 100 (those at high risk should reach a goal of less than 70) and HDL greater than 45
- Eat foods low in saturated fat and cholesterol and rich in fiber and nutrients (including antioxidants)
- Be active and exercise regularly
- Control high blood pressure and diabetes
- Achieve and maintain an appropriate weight
- Ask your doctor to do a blood test to detect high-sensitivity c-reactive protein a general marker of arterial inflammation an indicator of heart disease
- Have regular check-ups with your doctor
- Ask your doctor about taking aspirin (between 80 and 160 mg once a day)
- Antioxidant Vitamins Provide No Protection Against Heart Disease and May Increase Risk in Some Cases
- Vivekananthan DP, Penn MS, Sapp SK, Hsu A, Topol EJ. Use of antioxidant vitamins for the prevention of cardiovascular disease: meta-analysis of randomised trials 2003 Lancet 2003 June 14; 361: 2017–23. www.thelancet.com*
- Yusuf S, Davaenis G, Pogue J, Bosch, J, Sleight P. Vitamin E supplementation and cardiovascular events in high-risk patients. The Heart Outcomes Prevention Evaluation Study Investigators. New England Journal of Medicine 2000 Jan; 342(3):154-60
- Yusaf S. Vitamin E supplementation and cardiovascular events in high-risk patients. Correspondence . New England Journal of Medicine 2000 June; 342(5):1917-1918.
- Topol EJ and Califf RM. Clinical trial commentary: HPS. www.medscape.com/cardiology*
- Vitamin E: The Little Heart Health Supplement that Couldn't, Men's Health Advisor, Vol 5/Number4, April 2003
- Vitamin and Mineral Supplements *, American Heart Association
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