How green tea can kill cancer cells: compound destroys disease while leaving healthy cells unscathed

Author: Lizzie Parry

A compound in green tea has been found to kill mouth cancer cells while leaving healthy cells undamaged. While it was known the drink could help fight the disease, scientists say they have now worked out why. The breakthrough involved identifying the process by which the substance attacks cancer cells. This, it is hoped, will lead to new treatments for oral cancer, as well as other forms of the disease.

A compound found in green tea has been found to kill off oral cancer cells, while leaving healthy cells undamaged. Scientists at Penn State have now identified how the process targets the disease

A compound found in green tea has been found to kill off oral cancer cells, while leaving healthy cells undamaged. Scientists at Penn State have now identified how the process targets the disease

Scientists at Penn State University, in the US, explored the specific mechanism by which the green tea compound is able to target the diseased cells. Earlier studies have shown that epigallocatechin-3-gallate (EGCG), a compound found in green tea, killed mouth cancer cells without harming normal cells. But researchers did not understand the reasons behind the substance’s ability to kill the cancer cells. Scientists now believe EGCG may trigger a process in the mitochondria – the powerhouse of a cell that produces energy – that leads to cell death.

Professor Joshua Lambert, a specialist in food science and co-director of Penn State’s Center for Plant and Mushroom Foods for Health, said: ‘EGCG is doing something to damage the mitochondria.

‘That mitochondrial damage sets up a cycle causing more damage and it spirals out, until the cell undergoes programmed cell death.

‘It looks like EGCG causes the formation of reactive oxygen species in cancer cells, which damages the mitochondria, and the mitochondria responds by making more reactive oxygen species.’

Reactive oxygen species are chemically reactive molecules containing oxygen. They play an important role in cell signalling and homeostatsis – the control of internal conditions including temperature. When reactive oxygen species levels increase dramatically, it can cause significant damage to cell structures – this is known as oxidative stress. As this mitochondrial demise continues, the cancer cell also reduces the expression of antioxidant genes, further lowering its defences.

‘So, it’s turning off its mechanism of protection at the same time that EGCG is causing this oxidative stress,’ Professor Lambert added.

His team discovered the EGCG did not cause the same reaction in normal cells. In fact, the compound appeared to increase the healthy cell’s protective capabilities.

The researchers studied normal human oral cells, alongside human oral cancer cells, to determine how the compound was targeting the cancer cells differently to those healthy tissues. They grew the normal and cancer cells on petri dishes, before exposing them to EGCG – the major polyphenol found in green tea. They used concentrations of the compound typically found in the saliva after a person chews green tea gum. At specific times the scientists collected the cells to check for oxidative stress and signs of antioxidant response.

Professor Lambert, said: ‘We also took a lot of pictures, so we could use fluorescent dyes that measure mitochondrial function and oxidative stress and actually see these things develop.’

His team identified a protein called sirtuin 3 (SIRT3) is critical to the process.

‘It plays an important role in mitochondrial function and in antioxidant response in lots of tissues in the body, so the idea that EGCG might selectively affect the activity of sirtuin 3 in cancer cells – to turn it off – and in normal cells – to turn it on – is probably applicable in multiple kinds of cancers,’ said Professor Lambert.

This study builds on past research into how the compound affects oral cancer, a disease expected to kill more than 8,000 people in the US this year.

‘We’ve published one paper previously just looking at the effect of these green tea polyphenols on oral cancer cells in cultures,’ said Professor Lambert.

‘And there have been other papers published using oral cancer cells and at least a couple of animal model studies that have looked at oral cancer and prevention of oral cancer.’

He said the next step would be to study the mechanism in animals. If those tests and human trials were then successful, the scientists hope to create cancer treatments that are as effective as current ones, but without the harmful side effects.

Professor Lambert added: ‘The problem with a lot of chemotherapy drugs – especially early chemotherapy drugs – is that they really just target rapidly dividing cells, so cancer divides rapidly, but so do cells in your hair follicles and cells in your intestines, so you have a lot of side effects.

‘But you don’t see these sorts of side effects with green tea consumption.’

The study, supported by the American Institute for Cancer Research, was published in the online issue of Molecular Nutrition and Food Research.

February, 2015|Oral Cancer News|

Antioxidants May Cause More Harm Than Good in Cancer Patients

Author: Zosia Chustecka

While alternative health gurus often encourage increasing antioxidants in the diet and the taking of antioxidant nutritional supplements such as beta-carotene, vitamins A, C, and E, and selenium, new research findings suggest that antioxidants could do more harm than good, especially in cancer patients.

The idea is discussed in a perspective article on the promise and perils of antioxidants for cancer patients in the July 10 issue of the New England Journal of Medicine.

Coauthor David Tuveson, MD, PhD, professor and deputy director of the Cold Spring Harbor Laboratory Cancer Center in New York, explained in an interview with Medscape Medical News that the idea that antioxidants could be useful in cancer goes back to Linus Pauling, and is based on observations that oxidation within cells is needed for cell growth. “As cancer cells growth rapidly, a cancer cell would have more oxidation within it than a normal cell,” he added, and the hope was that antioxidants would interfere with these cellular oxidative processes and would suppress the growth.

“Although some early preclinical studies supported this concept,” the authors write, there have now been several clinical trials that have shown no effect of antioxidants on reducing the incidence of cancer, and there have even been suggestions of harm in persons who are at risk for cancer.

Dr. Tuveson noted a clinical trial from Scandinavia in the early 1990s, which found that high doses of antioxidants, particularly beta-carotene, were associated with more lung cancer rather than less as had been hoped for.

There was a similar finding from the Selenium and Vitamin E Cancer Prevention Trial (SELECT), which found that the antioxidants did not reduce the risk for prostate cancer, as had been hoped, and in fact increased the risk in some men.

Dose-dependent Harmful Effect

The perspectives article was prompted by new findings reported earlier this year, he said. An animal study carried out by Swedish researchers showed that the harm from antioxidants was dose-dependent (Sci Transl Med. 2014;6:221ra15). The study was conducted in a genetically engineered mouse model that mimics early human non-small-cell lung cancer. The researchers studied N-acetylcysteine (which is used in patients with chronic obstructive pulmonary disease) and also derivatives of vitamin E, and they found that these antioxidants “actually increased cancer burden and mortality in a dose-dependent manner.”

“The mice got lung cancer faster and they died more quickly of the disease,” Dr. Tuveson said.

In their perspective article, Dr. Tuveson and coauthor Navdeep Chandel, PhD, from Northwestern University in Chicago, address the question of why.

It turns out that all cells have not only oxidative mechanisms producing reactive oxygen species, they also have a mechanism by which they produce antioxidants, and so there is a balance between the 2 in each cell. “And cancer cells, because they make more oxidants, also make more antioxidants,” Dr. Tuveson explained.

“So when adding an antioxidant as a supplement, all you are doing is increasing a pool of what is already there,” he said. “But you are not actually stopping the oxidative mechanisms, and you are not stopping the production of oxidants in the first place, and the pathways that are fuelling cell growth,” he added.

“All you are doing is helping the cancer cell deal with the toxic effects of the oxidants, and by doing so you may be actually making the cancer cell even stronger,” Dr. Tuveson said.

“The antioxidants that we take as a supplement or in our diet don’t go after the root cause of how oxidants promote cancer cell biology,…and our suggestion is that we need to look much more carefully at these mechanisms if we are to truly develop strategies to prevent cancer,” he said.

In their article, the authors propose 2 strategies for further research — the development of antioxidants that target specific intracellular sites of oxidant production, and also a synthetic lethal strategy directed at antioxidants produced within the cell. Both of these strategies are currently at the research stage, with work focused on developing compounds that could be tested in humans.

As for the clinical implications of the research so far, Dr. Tuveson said: “We don’t firmly say that taking antioxidants is dangerous for cancer patients…but I do believe that our article will cause those discussions to begin.”

However, others have already warned cancer patients not to take antioxidants; for instance, prostate cancer patients have been warned against taking selenium, as previously reported by Medscape Medical News.

In addition, there is a question of whether antioxidants may interfere with common cancer treatments, such as chemotherapy and radiotherapy, as these work by increasing oxidation within cancer cells, Dr. Tuveson commented. This is an area that needs to be studied more, he said.

This issue of antioxidants being harmful to cancer patients was raised last year by Nobel laureate James Watson, PhD, who is chancellor emeritus at the Cold Spring Harbor Laboratory. He described a new hypothesis on reactive oxygen species that he considers is “among my most important work since the double helix.”

Dr. Watson proposed that antioxidant levels within cancer cells are a problem and are responsible for resistance to treatment, and that the untreatability of late-stage cancer might be the result of “its possession of too many antioxidants.”

“The time has come to seriously ask whether antioxidant use more likely causes than prevents cancer,” Dr. Watson said. Nutritional intervention trials have shown no obvious effectiveness in preventing cancer or in lengthening mortality, and, “in fact, they seem to slightly shorten the lives of those who take them.”

Dr. Tuveson, who works at the same institution, commented at the end of the interview that “Dr. Watson is usually a few steps ahead of the rest of us.”


 *This news story was resourced by the Oral Cancer Foundation, and vetted for appropriateness and accuracy.
July, 2014|Oral Cancer News|

Berry Nutrition

Author: Marie Spano, M.S., R.D., Contributing Editor

Nutritionally speaking, good things come in sweet—and tart—little packages. Research is discovering berries pack a nutritional punch due to their vitamin, fiber and antioxidant content.

Botanically speaking, berries are indehiscent fruits (they don’t need to be opened to release their seeds) that ripen through the ovary wall. However, any small, edible fruit with multiple seeds is typically considered a berry.

In addition to lending flavor and brilliant colors to a wide variety of dishes, all berries are packed with an array of antioxidants, nutrients and potential health benefits. Berries that are especially antioxidant-rich include fresh crowberries, bilberries, black currants, wild strawberries, blackberries, blueberries, goji berries, sea buckthorn, blueberries and cranberries. However, the antioxidant content of berries varies based on the geographical growing condition. And, while fresh berries are an excellent source of antioxidants, total phenol content drops during processing. In fact, processed berry jams and syrup contain approximately half the antioxidant capacity of fresh berries, and juices show the greatest loss of anthocyanins and tannins due to the removal of seeds and skin (Nutrition Journal, 2010; 9:3; Journal of Agricultural and Food Chemistry, Jan 13, 2012).

Botanical berries
Shiny, scarlet-colored cranberries are rich in vitamin C, loaded with antioxidants, including flavonoids, and score higher in their ORAC score than many other fruits (“Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods—2007”, USDA ARS). Cranberries are perhaps best known for the role their juice plays in the prevention of urinary tract infections (UTI) in women, particularly those with recurrent UTIs (Cochrane Database Systems Review, 2008; 23:CD001321). However, cranberries may also inhibit the growth and proliferation of some types of cancer cells (Journal of Nutrition, 2007; 137:186S-193S), reduce low-density lipoprotein (LDL) oxidation and platelet aggregation, and improve vascular function (Nutrition Reviews, 2010; 68:168-177; Nutrition Reviews, 2007; 65:490-502). In addition, polyphenols isolated from cranberries appear to inhibit the formation of cariogenic bacteria and reduce both inflammation and the production of enzymes that contribute to the destruction of the extracellular matrix in periodontal disease, making them beneficial for oral health (Journal of the Canadian Dental Association, 2010; 76:a130).

Processing and storage affects the phytochemicals found in cranberries. Anthocyanins are present at much higher levels than flavonols in cranberries, but the reverse is true for cranberry juice, due, in part, to the instability of anthocyanins. Some flavonols are also degraded during processing but to a lesser extent than anthocyanins (Critical Reviews in Food Science and Nutrition, 2009; 49:741-781).

Also leading the nutritional way is the tiny blueberry. According to the U.S. Highbush Blueberry Council, Folsom, CA, blueberries are packed with vitamin C, dietary fiber, potassium and antioxidants, with a total of 6,552 ORAC units per 100 grams. Further, many studies have indicated blueberry supplementation can help mitigate age-related neurodegenerative diseases. In one study, for example, rats fed 18.6 grams of dried blueberry extract per kilogram of diet for eight weeks showed a reversal of age-related deficits in brain and behavioral function (The Journal of Neuroscience, 1999; 19:8,114-8,121). The phytochemicals in blueberries also may help protect against some cancers. A study that identified blueberry anthocyanins also determined their ability to inhibit the growth of colon, breast, oral and, especially, prostate cancer cell lines. The same study showed blueberries were effective in inducing cell death of colon-cancer cells (Journal of Agricultural and Food Chemistry, 2006; 54:9,329-9,339).

Other less commonly consumed berries show promising health benefits. Though relatively few health-related studies have been conducted using black, white and red currants, one study using mixed berries, including currants, found that consumption of two portions of berries daily (including black currant purée on alternating days) resulted in favorable changes in high-density lipoprotein (HDL) cholesterol, blood pressure and platelet functioning (American Journal of Clinical Nutrition, 2008; 87:323-331). Red and black currants are an excellent source of vitamin C, and black currants are also an excellent source of fiber and good source of manganese and potassium.

Wolfberries, otherwise known as goji berries, contain several antioxidants, notably zeaxanthin, one of the two antioxidants found in the retina of the eye. One double-blind, placebo-controlled study in healthy elderly subjects found that, compared to placebo, daily supplementation with goji berry (13.7 grams per day) for 90 days increased plasma zeaxanthin and antioxidant levels while protecting from hypopigmentation and soft drusen accumulation (yellow deposits under the retina) in the macula of the eye (Optometry & Vision Science, 2011; 88:257-262). Additional studies have found that goji berry juice improves antioxidant biomarkers in healthy humans (Nutrition Research, 2009; 29:19-25), subjective feelings of well-being, neurologic and psychologic performance and gastrointestinal functioning (Journal of Alternative and Complementary Medicine, 2008; 14:403-412).

More research needs to be done on the health benefits of gooseberries and muscadine grape berries, but they, too, have a great nutrition profile. Gooseberries are an excellent source of vitamins A and C, and a good source of potassium and fiber. Muscadine grape berries are an excellent source of manganese, a good source of fiber and contain reseveratrol (American Journal of Enology and Viticulture, 1996; 47:57-62).

Non-botanical berries
In addition to the nutrition attributes for botanical berries, non-botanical berries, including strawberries, chokeberries, blackberries and raspberries, are also loaded with nutrients and antioxidants.

Strawberries are an excellent source of vitamin C and also contain fiber, vitamins, potassium and phytonutrients. Animal research has shown that strawberries improve indices of memory and cognitive functioning (Current Opinion in Clinical & Metabolic Care, 2009; 12:91-94), while human intervention studies indicate that strawberries (in addition to chokeberries, cranberries and blueberries; fresh, as juice or freeze-dried) lead to significant improvements in LDL oxidation, lipid peroxidation, dyslipidemia and glucose metabolism (Nutrition Reviews, 2010;6 8:168-177).

Chokeberries (Aronia melanocarpa) contain a mix of many antioxidants, including procyanidins, anthocyanins and phenolic acids. A review of studies to date on chokeberries indicate they may be a promising functional food for diseases related to oxidative stress, but more rigorous scientific research is necessary (Phytotherapy Research, 2010; 24:1,107-1,114).

Blackberries are an excellent source of vitamin C and fiber. Studies show anthocyanin-rich fractions of blackberry extracts reduce UV-induced free radical damage to skin cells (Phytotherapy Research, 2012; 26:106-112), and freeze-dried blackberries reduce esophagus and colon cancer development in rodents (Nutrition and Cancer, 2006; 54:69-78).

Raspberries are an excellent source of vitamin C, manganese and dietary fiber, and a good source of vitamin K. However, much of the interest in raspberries stems from their anthocyanin and ellagic acid content. In vitro studies show ellagic acid is protective against cancer (Journal of Nutrition and Biochemistry, 2004; 15:672-678). And this antioxidant, as well as the overall antioxidant capacity of raspberries, is similar in fresh commercial, freshly picked and frozen raspberries (Journal of Agricultural and Food Chemistry, 2002; 50:5,197-5,201).

All berries are full of antioxidants and nutrients. And, the various colors, textures and different forms of berries, including frozen, fresh, dried and pulp, make berries a versatile, nutritious, eye-appealing and tasty addition to a variety of foods and beverages.

About the author:
Marie Spano, M.S., R.D., CSCS, is a nutrition communications expert whose work has appeared in popular press magazines, e-zines and nutrition-industry trade publications. She has been an expert guest on NBC, ABC and CBS affiliates on the East Coast.

February, 2012|Oral Cancer News|

Meat ups cancer risk while fruit/vegetables reduce it

Author: staff

In 1976, the Senate Select Committee on Nutrition and Human Needs, led by Senator George McGovern found that meat-based diets are responsible for more than half of total cases of cancer. In 1980, the U.S. National Cancer Institute directed the National Research Council to collect and study the literature on nutrition and cancer. It found that eating meat causes 40 percent of cancers in males and 60 percent of total cancers in women.

International research institutions confirmed that the more the meat intake, the higher the risk for the cancer, particularly in the digestive system. Harvard University public health experts found 70 percent of human cancers are associated with meat consumption. U.S. National Institutes of Health studied fifty thousand vegetarians and found they had much lower risk for cancer than meat eaters.

At the University of Colorado Denver Health Sciences Center, Tim Bayer, Professor of Preventive Medicine, said fruits and vegetables are preventative against all gastrointestinal cancers and cancers induced by smoking. He also said it has been fully scientifically confirmed that eating fruits and vegetables prevents oral cancer , throat, esophagus, lung, stomach, colon and bladder cancer.

Chairman of the U.S. National Academy of Sciences Research Group and University of California biologist Dr. Clifford Grobstein said: “By controlling the food we eat, the diet can prevent sensitive cancers, such as esophagus, breast, stomach, colorectal and prostate cancer.”

Why does a vegetarian diet prevents cancer?

1. Fruits and vegetables contain anti-cancer ingredients

In 1978, the University of Minnesota researchers found that cauliflower ingredients like Indole can help prevent breast cancer and stomach cancer.

In 1992, University of California at Berkeley scholars reviewed 200 published studies of cancer published since 1980 and found that eating a lot of fresh fruits and vegetables can reduce the risk of liver cancer, stomach cancer, pancreatic cancer, colon cancer, bladder cancer, cervical cancer, ovarian cancer and endometrial cancer risk. People eating lots of fruits and vegetables are at 50 percent reduced risk for cancer, compared to those who do not eat fruits and vegetables often.

In 1997, the American Health Foundation confirmed that lycopene (lycopene) found in tomatoes is a powerful anti-oxidant, which helps prevent breast, prostate and gastrointestinal cancer. Harvard Medical School studies showed that lycopene may reduce the risk of breast, prostate and other cancer risk. Italian research found that people eating at least seven servings of tomatoes per week were at 50 percent reduced risk of cancer, compared with those eating four servings or less per week.

In 2003, University of Minnesota researchers found that ginger root contains an ingredient called “gingerol 6”, which plays a role in the prevention and treatment of colon cancer.

In 2003, the Cancer Council Victoria in Melbourne, Australia published a study of forty thousand men and women with different dietary habits suggesting eating more tomatoes, onions can prevent prostate cancer, eating sausages and red meat significantly can increase risk of cancer.

In 2004, Texas A&M University found that cauliflower, broccoli, turnip and mustard greens contain a substance called Diindolymethane, which inhibits the growth of breast cancer, pancreas cancer, colon cancer, bladder cancer and ovarian cancer.

In 2004, the French Association for International Health and Medicine found that apple peel contains a substance with antioxidantive activity can prevent colon cancer.

In 2005, a University of California study showed that regularly eating fruit, vegetables and grain products can help slow the progression of prostate cancer. University of California in conjunction with a cancer treatment center in New York analyzed 93 prostate cancer patients and found that they who chose to eat a vegetarian diet significantly improved their conditions.

In 2005, Dr. Farah Scarborough of University of London Sackler Institute found that eating beans, nuts and grains, can help prevent cancer, this is so because lentils and peas contain a natural compound called phosphate inositol inhibiting tumor growth. Researchers suggest that people should eat more beans, nuts, and grain products to help them prevent cancer.

In 2005, the University of Wisconsin School of Medicine Hassan? Professor Mukhtar series of experiments confirmed that the pomegranate is very rich in anti-cancer substances, inhibit cancer cells, prostate cancer is particularly effective.

In 2006, Professor Leibei Carrie at the University of Michigan Comprehensive Cancer Center conducted a study and found that ginger can kill cancer cells in two ways inducing apoptosis and cell autophagy.

In 2006, a University of Pittsburgh School of Medicine study found that capsaicin in peppers can cause death of cancer cells, the tumor is much narrower, and the spicy ingredient in chili capsaicin can kill pancreatic cancer cells, but does not affect the healthy pancreas cells.

In addition, the Singapore National Cancer Center researchers found that fruit and vegetables including tomatoes, apples, onions, peppers and other red grapes contain kaempferol, certain flavinoids and other ingredients that can prevent angiogenesis of cancer cells and can prevent breast cancer and other cancers. It is suggested that daily consumption of two ladies to the three red fruits and vegetables.

Researchers around the world also found that soy contains isoflavones (Isoflavones) which can inhibit breast cancer, colorectal cancer, oral cancer, lung cancer and liver cancer; carrots containing vitamin A help fight liver cancer. In addition, the polysaccharide Hericium (Hericium Erinaceus polysauharides, HEP), isothiocyanate salts (Isothiocyanates) in cabbage, elagic acid in grapes, gum in watermelon, Glucarase in citrus fruits, lemon limonene (limonene ) and green tea polyphenols (Polyphenols) have anti-tumor properties. Meanwhile, garlic can not only block the formation of cancer-causing nitrosamines in the body, but also stimulate macrophage phagocytosis of human cancer cells.

2. Fruits and vegetables contain low-fat and high-fiber

Large amounts of vegetarian cellulose can stimulate the bowel movement, which will help purge feces and get rid of harmful substances quickly, reducing the risk of rectal cancer and colon cancer.

One American cancer expert said: “The vegetarian diet is low in protein and fat and high in fiber, so vegetarians have nearly a zero risk of colon cancer!”

David Jenkins. a fiber expert at University of Toronto in Canada also said: “The fiber is very effective in the prevention of colon cancer.”

3. sodium and potassium ratio

At M.D. Anderson Cancer Center of University of Texas, Dr. Jansson found that intakes of potassium and sodium may affect the development of cancer. An analysis of data from 20 countries shows that incidence of cancer is low in the area where people had high intake of potassium. Potassium is very rich in vegetables and legumes.

University of Texas M.D. Anderson Cancer Center researchers pointed out that the intracellular potassium is about 10 times higher than sodium. In order to maintain normal cell function, cells must absorb sufficient potassium. If damaged cells lose potassium, it will immediately begin to reproduce division. If the ratio of potassium to sodium is lower than that of normal cells, the growth of cells will continue. The growth of cancer cells is directly related to the ratio of potassium to sodium.

Potassium rich foods include dried herbs, avocados, paprika/red chili powder, cocoa power and chocolate, dried apricots, prunes, zante currants and raisins, pistachios, seeds such as pumpkin seeds, squash, sunflower and flaxseed,fish such as pompano, salmon, halibut and tuna, beans and dates. Other potassium rich foods include bananas, orange juice, sun dried tomatoes, palm hearts, baked potatoes, molasses, rice bran, sweet potatoes, and Brussels Sprouts.

Meats contain lower ratios of potassium to sodium.

Studies suggest that the normal intake ratio of potassium to sodium should be 2 t 1. Data from U.S. Department of Agriculture show that ratios of potassium to the sodium in banana, pumpkin, soy, orange, and ordinary fruit and vegetables are 380, 360, 331, 221; and more than 200 respectively. Conversely, the ratios for chicken, duck, fish are no more than 3-5. There is no doubt that the high sodium low potassium meat greatly increased the chances of human cancer.

4. research findings from China

A panel of researchers at Beijing Union Medical College Hospital and other organizations conducted a survey and found meat and cancer are related. The survey found the incidence of cancer in Beijing in 1996 was 5.2 times as high as that in 1955. The high cancer risk was associated with a diet with increasing intake of meat and decreasing intake of fiber-rick vegetables.

Another medical report by the Panel said: “Our country had originally low incidence of colorectal cancer, less than ten hundred thousandths (10/100,000). But in the last two to three years with the changes in the structure of food, an increase in meat consumption, the cancer incidence has risen since 2000 to the twenty-four hundred thousandths (24.31/100,000), equivalent to moderate incidence in other countries.

Experts believe that the increased incidence of bowel cancers has something to do with environmental factors including diet, increasing consumption of meat, refined food products and lack of cellulose and fiber rich foods such as grains, cereals. High-fat, high protein diet is associated with increased risk of breast cancer, colorectal cancer.

People who really want to reduce their risk of cancer should reduce their intake of meats and increase dietary intake of fruit and vegetables.

1. This article is a work of translation and names of people and organizations may not be entirely accurate.

December, 2011|Oral Cancer News|

Effects of antioxidant supplements on cancer prevention: meta-analysis of randomized controlled trials

Source: Ann. Onc., July 21, 2009
Author: S-K Myung et al.

This meta-analysis aimed to investigate the effect of antioxidant supplements on the primary and secondary prevention of cancer as reported by randomized controlled trials.

We searched Medline (PubMed), Excerpta Medica database, and the Cochrane Review in October 2007.

Among 3327 articles searched, 31 articles on 22 randomized controlled trials, which included 161 045 total subjects, 88 610 in antioxidant supplement groups and 72 435 in placebo or no-intervention groups, were included in the final analyses. In a fixed-effects meta-analysis of all 22 trials, antioxidant supplements were found to have no preventive effect on cancer [relative risk (RR) 0.99; 95% confidence interval (CI) 0.96-1.03). Similar findings were observed in 12 studies on primary prevention trials (RR 1.00; 95% CI 0.97-1.04) and in nine studies on secondary prevention trials (RR 0.97; 95% CI 0.83-1.13). Further, subgroup analyses revealed no preventive effect on cancer according to type of antioxidant, type of cancer, or the methodological quality of the studies. On the other hand, the use of antioxidant supplements significantly increased the risk of bladder cancer (RR 1.52; 95% CI 1.06-2.17) in a subgroup meta-analysis of four trials.

The meta-analysis of randomized controlled trials indicated that there is no clinical evidence to support an overall primary and secondary preventive effect of antioxidant supplements on cancer. The effects of antioxidant supplements on human health, particularly in relation to cancer, should not be overemphasized because the use of those might be harmful for some cancer.

S-K Myung, Y Kim, W Ju, H J Choi, and W K Bae

Authors affiliation:
Center for Cancer Prevention and Detection, National Cancer Center, Goyang