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October 23, 2008
Antioxidants help prevent oxidation, may help increase immune function and possibly decrease risk of infection and cancer. Antioxidants exist as vitamins, minerals and other compounds in foods (http://www.eatright.org/cps/rde/xchg/SID-5303FFEA-845A50FB/ada/hs.xsl/home_4634_ENU_HTML.htm).
Just like rust on a car, oxidation can cause damage to cells and may contribute to aging.
The ancients had a purpose for antioxidants, even without understanding the chemistry behind their use or the health benefits of them. The ancient Greeks and Romans, for example, would use oils high in antioxidants for preserving food. They might not have totally understood the whys, or even knew they were using antioxidants, but they knew they could keep food better longer (http://www.customvitaminshop.com/purpose-of-antioxidants.php). Today, however, we see another purpose of antioxidants: fighting free radicals. Antioxidants have had proven success against free radicals, but the question is, can antioxidants alone prevent the onset of cancers and other diseases in the human body?
Free Radical and Antioxidant 101
Numerous studies have shown that free radicals can pose significant damage to our health, including even leading to cancer. Antioxidants are proven to help fight against free radicals, and are intimately involved in the prevention of cellular damage -- the common pathway for cancer, aging, and a variety of diseases. Free radicals are atoms or groups of atoms with an odd (unpaired) number of electrons and can be formed when oxygen interacts with certain molecules through a process known as oxidation. Because free radicals are missing an electron, they are deemed unstable molecules. Molecules strive for balance, so a free radical, missing an electron, is going to attach itself onto the nearest stable molecule it can find and steal one of its electrons. The problem is this could turn the new molecule into a free radical, which will then find another molecule to steal an electron from, causing a chain reaction. Free radicals, in and of themselves, are not necessarily harmful. In fact, they are a vital part of our body's systems and are created naturally in the body. Problems come, however, when there are too many free radicals in the body. Thus we need antioxidants to create balance of free radicals in the body by safely interacting with the free radicals and ceasing the chain reaction before vital molecules are destroyed (http://www.customvitaminshop.com/purpose-of-antioxidants.php).
The principal antioxidants include the following micronutrients:
Vitamin E : d-alpha tocopherol. A fat soluble vitamin present in nuts, seeds, vegetable and fish oils, whole grains (esp. wheat germ), fortified cereals, and apricots.
Vitamin C : Ascorbic acid is a water soluble vitamin present in citrus fruits and juices, green peppers, cabbage, spinach, broccoli, kale, cantaloupe, kiwi, and strawberries
Beta-carotene is a precursor to vitamin A (retinol) and is present in liver, egg yolk, milk, butter, spinach, carrots, squash, broccoli, yams, tomato, cantaloupe, peaches, and grains. Because beta-carotene is converted to vitamin A by the body there is no set requirement. (NOTE: Vitamin A has no antioxidant properties and can be quite toxic when taken in excess.)
Selenium is a trace metal that is required for proper function of one of the body's antioxidant enzyme systems. Sources of selenium include: fish & shellfish, red meat, grains, eggs, chicken and garlic
Other Common Antioxidants
Flavonoids/Polyphenols: soy, pomegranate, cranberries, blueberries, red wine, green tea
Lycopene: tomatoes, pink grapefruit, watermelon
Lutein: dark greens
Lignan: flax seed, oatmeal, barley, rye
It is important to remember that because the body does not produce the aforementioned micronutrients that they must be ingested in one’s daily diet.
What Claims are Made about Antioxidants?
The claimed curative and preventive effects of antioxidants are vast and well advertised to consumers. Some websites advertise the effects of antioxidants in order to push their so-called “miracle supplements” that prevent aging and increase the length of your life, such as Ondrox™, which claims to boost immunity and “give you life” (http://www.ondrox.com/ ) whereas other websites promote antioxidants for the simple benefit of promoting healthy habits, such as the US Dept. of Agriculture (http://fnic.nal.usda.gov/nal_display/index.php?info_center=4&tax_level=1). Remember when it was suggested that adults should drink red wine in moderation because it consists of flavonoids which are supposed to decrease heart disease, or the claim that the antioxidants in dark chocolate would also decrease heart disease rates? It’s claimed that chocolate contains antioxidants that may help prevent cholesterol from sticking to artery walls, reducing your risk of a heart attack or stroke. The darker the chocolate, the more antioxidants and flavonoids it contains (http://www.eatright.org/cps/rde/xchg/ada/hs.xsl/home_4528_ENU_HTML.htm). Additionally, lycopene has been touted as a measure against prostate cancer (http://www.eatright.org/cps/rde/xchg/SID-5303FFEA-A120B9BE/ada/hs.xsl/nutrition_5328_ENU_HTML.htm). The examples are endless, and they all stem from the thought that because antioxidants are supposed to prevent cellular aging and wear, then the hypothesis is that the body and its immune defenses becomes more resistant to infection and chronic diseases such as diabetes, heart disease, cancer, and others.
Is there scientific evidence to support these claims?
Numerous studies have been conducted in order to provide confirmation, or in some cases doubts, as to whether or not antioxidants do all they are claimed to. In a 1995 Harvard University study conducted with 47,894 men, researchers found that eating 10 or more servings a week of tomato products was associated with a reduced risk of prostate cancer by as much as 34 percent. (http://www.eatright.org/cps/rde/xchg/SID-5303FFEA-A120B9BE/ada/hs.xsl/nutrition_5328_ENU_HTML.htm) However, there was no mention of their exercise habits or whether or not they participated in unhealthy risky behaviors that would affect their susceptibility to cancer.
The initial findings of another study, the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (ATBC Study) indicated, however, that lung cancer incidence was increased among participants who received beta-carotene as a supplement. Researchers examined the effects of alpha-tocopherol and beta-carotene supplementation on the incidence of lung cancer across subgroups of participants in the ATBC Study defined by base-line characteristics (e.g., age, number of cigarettes smoked, dietary or serum vitamin status, and alcohol consumption), by study compliance, and in relation to clinical factors, such as disease stage. A total of 29,133 men aged 50-69 years who smoked five or more cigarettes daily were randomly assigned to receive alpha-tocopherol (50 mg), beta-carotene (20 mg), alpha-tocopherol and beta-carotene, or a placebo daily for 5-8 years (median, 6.1 years). Data regarding smoking and other risk factors for lung cancer and dietary factors were obtained at study entry, along with measurements of serum levels of alpha-tocopherol and beta-carotene. No overall effect was observed for lung cancer from alpha-tocopherol supplementation ( because relative risk [RR] = 0.99; 95% confidence interval [CI] = 0.87-1.1). beta-Carotene supplementation was associated with increased lung cancer risk ( because RR = 1.16; 95% CI = 1.02-1.33). The beta-carotene effect appeared stronger, but not substantially different, in participants who smoked at least 20 cigarettes daily (RR = 1.25; 95% CI = 1.07-1.46) compared with those who smoked five to 19 cigarettes daily (RR = 0.97; 95% CI = 0.76-1.23) and in those with a higher alcohol intake (> or = 11 g of ethanol/day [just under one drink per day]; RR = 1.35; 95% CI = 1.01-1.81) compared with those with a lower intake (RR = 1.03; 95% CI = 0.85-1.24) (1996). The conclusion that was come to is that supplementation with alpha-tocopherol or beta-carotene does not prevent lung cancer in older men who smoke. However, it may play a role in the prevention of lung cancer for younger men. It must be kept in mind that the study was done only on men aged 50-69, who probably had undergone years of smoking, drinking, and other unhealthy behaviors. Antioxidants may in fact play a role in prevention in younger men, but if course, more research is needed to determine that. Beta-Carotene supplementation at pharmacologic levels may modestly increase lung cancer incidence in cigarette smokers, and this effect may be associated with heavier smoking and higher alcohol intake.
In another study testing the feasibility and efficacy of a dietary intervention based on daily intake of flavanol-containing cocoa for improving vascular function of medicated diabetic patients, it was found that flavonoids do in fact reduce cardiovascular risk. In a feasibility study with 10 diabetic patients, researchers assessed vascular function as flow-mediated dilation (FMD) of the brachial artery, plasma levels of flavanol metabolites, and tolerability after an acute, single-dose ingestion of cocoa, containing increasing concentrations of flavanols (75, 371, and 963 mg). In a subsequent efficacy study, changes in vascular function in 41 medicated diabetic patients were assessed after a 30-day, thrice-daily dietary intervention with either flavanol-rich cocoa (321 mg flavanols per dose) or a nutrient-matched control (25 mg flavanols per dose). Both studies were undertaken in a randomized, double-masked fashion. Primary and secondary outcome measures included changes in FMD and plasma flavanol metabolites, respectively. A single ingestion of flavanol-containing cocoa was dose-dependently associated with significant acute increases in circulating flavanols and FMD (at 2 h: from 3.7 +/- 0.2% to 5.5 +/- 0.4%, p < 0.001). A 30-day, thrice-daily consumption of flavanol-containing cocoa increased baseline FMD by 30% (p < 0.0001), while acute increases of FMD upon ingestion of flavanol-containing cocoa continued to be manifest throughout the study. A resulting conclusion of the study showed that diets rich in flavanols reverse vascular dysfunction in diabetes, highlighting therapeutic potentials in cardiovascular disease (2008), however it is important to remember that this study was done on diabetic patients, and not on disease-free patients. By excluding diabetes free patients in this study, unintended theories have resulted. It could be inferred that flavonoids only have this effect on diabetics and not the greater healthy population. However, if antioxidants can improve the vascular function that is so greatly compromised by diabetes, then it more than likely can help prevent or reduce the risk of damage in a healthy system.
So, are antioxidants worth the hype?
While scientific research has found overall health benefits to the consumption of antioxidants, there is no reason to believe that deliberate consumption of antioxidant supplements alone will prevent the onset of chronic disease. However, it is important to couple antioxidant consumption with exercise, avoidance of unhealthy behaviors, and a diet rich in micronutrients needed to continue healthy body function. As seen in the aforementioned lung cancer study, antioxidants can have an adverse affect on health. There has been suggestion that while too many free radicals in the body are dangerous, too many antioxidants are dangerous as well. It is important to maintain balance in the body, and a shift in either direction could be harmful to the body. Antioxidant vitamins do indeed have potential health-promoting properties. However, it is important to remember to couple a diet rich in antioxidants to lead an overall healthy lifestyle, and to not follow the hype behind the antioxidant craze, and oversupplement the body with antioxidants. Though the data are incomplete, up to 30 percent of Americans are taking some form of antioxidant supplement (http://www.americanheart.org/presenter.jhtml?identifier=4452), which is indicative of the extent to which consumers are buying into the hype of antioxidants.
Albanes, D., Heinonen, O.P., Taylor. P.R., Virtamo, J., Edwards, B.K., Rautalahti, M., Hartman, A.M., Palmgren, J., Freedman, L.S., Haapakoski, J., Barrett, M.J., Pietinen, P., Malila, N., Tala, E., Liippo, K., Salomaa, E.R., Tangrea, J.A., Teppo, L., Askin, F.B., Taskinen, E., Erozan, Y., Greenwald, P., Huttunen, J.K. (1996) Alpha-Tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene cancer prevention study: effects of base-line characteristics and study compliance. Journal of the National Cancer Institute, (88)21, 1560-1570.
Balzer, J., Rassaf, T., Heiss, C., Kleinbongard, P., Lauer, T., Merx, M., Heussen, N., Gross, H., Keen, C., Schroeter, H. (2008) Sustained benefits in vascular function through flavanol-containing cocoa in medicated diabetic patients a double-masked, randomized, controlled trial. Journal of the American College of Cardiology, (51)22, 2141 – 2149.
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