Why is antioxidants important

Lung disease A study from the Journal of Respiratory Research found that different isoforms of vitamin E called tocopherols had opposing effects on lung function. Cancer When it comes to cancer prevention, the picture remains inconclusive for antioxidant supplements.

MAX randomized placebo-controlled trial showed a reduction in cancer risk and all-cause mortality among men taking an antioxidant cocktail low doses of vitamins C and E, beta-carotene, selenium, and zinc but no apparent effect in women, possibly because men tended to have low blood levels of beta-carotene and other vitamins at the beginning of the study.

Age-related eye disease A six-year trial, the Age-Related Eye Disease Study AREDS , found that a combination of vitamin C, vitamin E, beta-carotene, and zinc offered some protection against the development of advanced age-related macular degeneration, but not cataracts, in people who were at high risk of the disease. However, relatively short trials of lutein supplementation for age-related macular degeneration have yielded conflicting findings.

The study found that people taking the vitamins were less likely to progress to late-stage AMD and vision loss. However, the study authors noted that taking lutein and zeaxanthin alone or vitamin E alone did not have a beneficial effect on these eye conditions.

It did not find that antioxidant supplements of vitamin E or selenium, alone or in combination, protected against dementia compared with a placebo. Early death A meta-analysis of 68 antioxidant supplement trials found that taking beta-carotene and vitamin A and E supplements increased the risk of dying. It was also difficult to compare interventions because the types of supplements, the dosages taken, and the length of time they were taken varied widely. The same authors conducted another systematic review of 78 randomized clinical trials on antioxidant supplements including beta-carotene, vitamin A, vitamin C, vitamin E, and selenium alone or in combination.

The study found that both people who were healthy and those with diseases taking beta-carotene and vitamin E supplements had a higher rate of death. The duration of the studies varied widely from one month to 12 years, with varying dosages. The first inkling came in a large trial of beta-carotene conducted among men in Finland who were heavy smokers, and therefore at high risk for developing lung cancer.

The trial was stopped early when researchers saw a significant increase in lung cancer among those taking the supplement compared to those taking the placebo. Again, an increase in lung cancer was seen in the supplement group. MAX trial, rates of skin cancer were higher in women who were assigned to take vitamin C, vitamin E, beta-carotene, selenium, and zinc.

Antioxidants: In Depth. The total antioxidant content of more than foods, beverages, spices, herbs and supplements used worldwide. Nutrition journal. Resveratrol levels and all-cause mortality in older community-dwelling adults. JAMA internal medicine. Archives of internal medicine. Effects of long-term vitamin E supplementation on cardiovascular events and cancer: a randomized controlled trial.

Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. The Lancet. Vitamin E supplementation reduces cardiovascular events in a subgroup of middle-aged individuals with both type 2 diabetes mellitus and the haptoglobin genotype: a prospective double-blinded clinical trial.

Arteriosclerosis, thrombosis, and vascular biology. Lack of effect of long-term supplementation with beta carotene on the incidence of malignant neoplasms and cardiovascular disease. New England Journal of Medicine. The SU. MAX Study: a randomized, placebo-controlled trial of the health effects of antioxidant vitamins and minerals. Respiratory research. Isoforms of vitamin E have opposing immunoregulatory functions during inflammation by regulating leukocyte recruitment.

The Journal of Immunology. Baseline characteristics and the effect of selenium supplementation on cancer incidence in a randomized clinical trial: a summary report of the Nutritional Prevention of Cancer Trial.

Cancer Epidemiology and Prevention Biomarkers. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no.

Archives of ophthalmology. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E and beta carotene for age-related cataract and vision loss: AREDS report no.

Archives of Ophthalmology. Double-masked, placebo-controlled, randomized trial of lutein and antioxidant supplementation in the intervention of atrophic age-related macular degeneration: the Veterans LAST study Lutein Antioxidant Supplementation Trial. Optometry-Journal of the American Optometric Association. Bartlett HE, Eperjesi F. Effect of lutein and antioxidant dietary supplementation on contrast sensitivity in age-related macular disease: a randomized controlled trial.

European journal of clinical nutrition. The foods you eat supply other antioxidants, such as vitamins C and E. Plants are full of compounds known as phytochemicals—literally, "plant chemicals"—many of which seem to have antioxidant properties as well. For example, after vitamin C has "quenched" a free radical by donating electrons to it, a phytochemical called hesperetin found in oranges and other citrus fruits restores the vitamin C to its active antioxidant form.

Carotenoids such as lycopene in tomatoes and lutein in kale and flavonoids such as flavanols in cocoa, anthocyanins in blueberries, quercetin in apples and onions, and catechins in green tea are also antioxidants.

News articles, advertisements, and food labels often tout antioxidant benefits such as slowing aging, fending off heart disease, improving flagging vision, and curbing cancer. And laboratory studies and many large-scale observational studies those that query people about their eating habits and supplement use and then track their disease patterns have noted antioxidant benefits from diets rich in them, particularly those coming from a broad range of colorful vegetables and fruits.

But results from randomized controlled trials of antioxidant supplements in which people are assigned to take specific nutrient supplements or a placebo have not supported many of these claims. Indeed, too much of these antioxidant supplements won't help you and may even harm you. It is better to supply your antioxidants from a well-rounded diet. As a service to our readers, Harvard Health Publishing provides access to our library of archived content.

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