Written by: Haroun Zayed
The word antioxidant contains the prefix “anti: which means against or in opposition to. In this case it refers to oxidants or oxidation (Valko, et al, 2004). This infers that antioxidants are molecules with in our body that slow down or prevent the oxidation of other molecules. Examples of antioxidants include vitamin C, (ascorbic acid), a-tocopherol (vitamin E), Beta carotene, and lycopene. Although oxidation reactions are crucial for the life, they also can be damaging. This is because oxidation reactions could create free radicals. Free radicals are very unstable molecules that react very quickly with other compounds by means of stealing electrons (Valko, et al, 2004). This causes the attacked compound to become an unstable free radical. This begins a chain reaction that can cascade through molecules with in our body and finally result in the disruption of a living cell. Normally the human body would be able to control free radicals, but if antioxidants are unavailable, or there is an excess of free radicals then oxidative stress can occur which can damage cells (Valko, et al, 2004).
Oxidative stress describes the steady state level of oxidative damage to a cell tissue, or organ, cause by Reactive Oxygen Species (ROS) (Block, 2004). Oxidative stress is determined by the balance between the rate at which oxidative damage is induced, and the rate at which it is effectively repaired or removed: table 1 (Block,2004). Examples of ROS’s include Hydrogen peroxide (H2O2), hypochlorus acid (HCLO), hydroxyl radical (·OH), and the superoxide anion (O2−). These ROS’s can damage cells by starting chemical chain reactions such as lipid peroxidation, DNA oxidation and protein oxidation (Block, 2004). DNA oxidation can cause harmful damage that may lead to mutations, and possibly cancer. On the other hand protein oxidation can cause the inhibition of vital enzymes.
Theory
Cancer is the second leading cause of death in the U.S and Canada. The American Cancer Society estimates around 553 888 deaths in 2004. While in Canada it is estimated that 66 947 people died from cancer in 2004. Cancer can be caused by reactive oxygen species (ROS) which can increase inflammation and exposure to exogenous sources (Collins, 2005). This includes nitrogen oxide pollutants, smoking, certain drugs and radiation. All can induce cancer causing mutations by the oxidation of lipids, proteins, and the alteration of signal transduction pathways that enhance cancer risk (Borek, 2004). The idea is that an increase intake of antioxidants will prevent ROS from oxidizing and mutating cells to form cancer. However if a cancer patient is treated with radiation or chemotherapy and undergoes supplementation of antioxidants, problems may occur. can induce apoptosis (programmed cell death, suicide) to only cancerous cells (Borek, 2004) .
On the other hand Cardiovascular Disease (CVD) is the number one cause of death in the U.S and Canada. The American Heart Association estimates a total death count of 945 836 from CVD in 2004. Stats Canada estimates a total death count of 74 626 in 2002 from CVD in 2002. CVD is caused by atherosclerosis, an arterial disease which causes plaques with in medium sized arteries causing a heart attack or stroke (Vivekananthan, et al, 2003). The build up of plaque in atherosclerosis consists of foam cells whose cytoplasms are filled with cholesterol. These plaques are usually narrow and longitudinally oriented. Now it is believed that the oxidative modification of Low-Density Lipoproteins (LDL) by free radicals will result in their consumption by macrophages (Clarke, Armitage, 2002). This causes the macrophages to become foam cells that release cell agitating cytokines and free radicals which promote death and ruptures with in atherosclerosis plaques (Clarke, Armitage, 2002). The plaques would then begin to break up and form other plaques with in the same or smaller arteries. Repetition of this process will cause complete obstruction of the blood thus causing a stroke or a heart attack. Therefore the intake of antioxidants would prevent the free radicals from oxidizing LDL and help prevent heart attacks and strokes.
Discussion
In total 138 133 patients who were given Beta Carotene or a control treatment showed no effect on preventing all cause mortality or cardiovascular death. If anything it showed that Beta Carotene might in fact increase the rate of all cause mortality and cardiovascular death. This is shown in tables 2 and 3 were the absolute even rates of all most all of the trials presented a higher beta- carotene rate then the control rate. The CI value also indicates that the results were either insignificant or a slight increase because of the usage of beta carotene. As for the 82 000 patients who were given vitamin E there was no significant increase or decrease in all cause mortality or cardiovascular death. Finally through the little information on vitamin C and its ability to prevent cardiovascular death, there was no significant increase or decrease in cardiovascular disease.
From the 29 133 male smokers in the ATBC trial all the risk ratios were calculated for lung, colorectal, urothelial, prostate, and renal cell cancers. Although prostate cancer had the greatest relative risk reduction none of the studies individually showed a statistically significant result. The same trend was observed in the linxian and linxian dysplasia trials. In these trials supplements were given in combination and alone and still there was no statistically significant result to whether they have a benefit of survival. As for other trials that tested the efficiency of vitamin C on cancer there was no statistically significant result to show a benefit for survival. Finally there has been much speculation over the effect of lycopene on cancer. From the results in table 10 there seems to be a significant reduction in prostate, pancreatic, lung, breast, stomach, and colorectal cancer. Most notable is the protective effect of lycopene on prostate cancer. In a study of 47000 men, those who consumed 10 half-cup servings of tomato products per week had a 35% lower risk of developing prostate cancer compared to men who never ate tomato products (Hwang, Bowen, 2002). As for the other cancer sites there is significant reduction because of lycopene but till of now there hasn’t been large randomised clinical trials to further prove the protective effects of lycopene.
Note: All tables can be found at the end of the magazine. Found on p.58-64
Conclusion
In conclusion the results support the null hypothesis. Antioxidants do not have an effect on cardiovascular disease or cancer. In fact some antioxidants such as B-carotene increase the risk of Cardiovascular disease. As for the rest of the results there were no significant results to show any benefit of antioxidants on cardiovascular disease. The same was seen for cancer where there was no significant effect of antioxidants on many types of cancers. The only significant effect that occurred to cancer was from lycopene, an antioxidant found in tomatoes. There was a reduction in all cancer sites but most noticeably in prostate cancer. Therefore the following recommendations should be taken after consulting you family physician:
1.Stop the intake of antioxidant supplements in the favour of fruit and vegetable intake.
2.Increase the consumption of fruits and vegetables to more than 5 serving a day.
3.Stop the intake of B-carotene for previous or present smokers.
4.Those at risk or currently have prostate cancer should increase the intake of tomato products to provide more than 6 mg of lycopene a day5.Include better life style habits into your daily routine such as regular physical exercise, avoidance of cigarette smoke etc.
In all we still don’t know how fruits and vegetables have a protective effect against cancer but it seems that it isn’t because of their abundance of antioxidants. Further studies would have to be done to look into the combination of substances with in fruits and vegetables that have a protective effect against cancer.
Bibliography
Block, Keith I. "Antioxidants and Cancer Therapy:Furthering the Debate." Integrative Cancer Therapies (2004): 342-348.
This was primarily used for information on antioxidants and their mechanism of function
Borek, Carmia. "Dietary Antioxidants and Human Cancer." Integrative Cancer Therapies (2004): 333-341.
This article was not used extensively. Only minor sections pertaining to the effect of antioxidants was looked at.
Collins, Andrew R. "Antioxidant intervention as a route to cancer prevention." European Journal of Cancer (2005): 1923–1930.
Similar to the one above, only small sections were used that looked at reactive oxygen species.
Deepak. P. Vivekananthan, et al. "Use of antioxidant vitamins for the prevention of cardiovascular." The Lancet (2003): 2017-2022.
One of the most looked at articles. Results were used from this particular article as well as extensive information on atherosclerosis.
Eun-Sun Hwang, Phyllis E. Bowen. "Can the Consumption of Tomatoes or Lycopene Reduce Cancer Risk." Integrative Cancer Therapies (2002): 121-132.
Another well used article for results , and information on one of the few promising antioxidants. Very informative and helpful information on cancer trials.
Ian D. Coulter, et al. "Antioxidants Vitamin C and Vitamin E for the Prevention and Treatment of Cancer." Journal of General Internal Medicine (2006): 735-744.
This was mostly used for its extensive results on the affect of vitamins on a variety of cancers. However some information was obtained regarding future recommendation for cancer patients.
Marian Valko, et al. "Role of oxygen radicals in DNA damage and cancer incidence." Mollecular and Cellular Biochemistry (2004): 37-56.
This article was thoroughly used for its information on free radicals. Helped a lot in providing the reader with a better understanding of free radicals and cancer.
Robert Clarke, Jane Armitage. "Symposium: Vitamin Therapy and Ischemic Heart Disease: Antioxidant Vitamins and Risk of Cardiovascular Disease." Cardiovascular Drugs and Therapy (2002): 411-415.
This article was one of the most used. It provided a great deal of results as well as information on cardiovascular disease and possible explanations for antioxidant use.
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