A recent study that was widely disseminated by the press purported to show (in the authors’ conclusions and much of the media reports) that taking almost any vitamin C (and especially high doses) would interfere with chemotherapy treatment for cancer. The study had two arms, including both tissue culture and animal testing (using mice). I’ll get to the significance of the mice later, but for now, I think the data do not show that vitamin C interferes with cancer treatment, and it very likely has benefits for cancer patients.
This study has some serious flaws (Heaney ML, et al., Vitamin C antagonizes the cytotoxic effects of antineoplastic drugs. Cancer Res. 2008 Oct 1;68(19):8031-8). One of the most glaring is not found in the abstracts or in any of the media reports, but was noted to me by a colleague in Japan (Atsuo Yanagisawa, MD, a cardiologist and former medical college professor) when I was recently in Japan teaching at a conference.
Vitamin C is an antioxidant, and many of its benefits result from the protection that this action provides to cells and tissues. In this study, they pre-incubated the vitamin C with an enzyme, vitamin C oxidase, which produces the oxidized form of vitamin C, dehydroascorbate. Oxidized vitamin C does not have the same benefits that are found with the reduced ascorbate molecule. However, in a complex array of chemical reactions, vitamin C can act as a pro-oxidant in cancer cells, leading to the cells’ death.
Chemotherapy agents act by producing reactive oxygen species, which is why theories have been proposed that vitamin C would interfere with the treatment, but if you give the already-oxidized dehydroascorbate, the relationship becomes very complex, and I cannot see how it would be possible to draw valid conclusions.
Another fault with the study, and one that makes it unlikely to apply to humans, is that mice make their own vitamin C in relatively high amounts. Some estimates are that mice can make the equivalent of 10,000 mg daily (adjusted for human body weight). In this study they used 2000 mg of pre-oxidized vitamin C. Animals that make their own vitamin C (and that includes all but primates, guinea pigs, and fruit-eating bats) increase their production when they are under stress or are sick, such as when they have cancer or infections.
Given all these flaws, it is impossible to draw any conclusions from this study about the effects of vitamin C in cancer patients, with or without chemotherapy. Other studies show that vitamin C can have profound beneficial effects in patients with cancer. A study from the National Institutes of Health showed that very high doses of vitamin C, administered intravenously, slowed the growth of aggressive cancers, such as ovarian, pancreatic, or glioblastoma, even in mice. (Chen Q, et al., Pharmacologic doses of ascorbate act as a pro-oxidant and decrease growth of aggressive tumor xenografts in mice. Proc Natl Acad Sci U S A. 2008 Aug 12;105 (32):11105-9.) The treatment produced hydrogen peroxide and had cell-killing effects, but only in the tumors, not in the normal cells. This is unlike chemotherapy, which is also toxic to normal cells.
Linus Pauling and Ewan Cameron showed in 1976 and 1981 that high doses of oral vitamin C prolonged the lives of cancer patients. Some studies, but not all, show that vitamin C and other vitamins, such as vitamin E, are also helpful in preventing cancer. It would be tragic if patients with cancer were misled into thinking that they should not take vitamin C and other supplements along with their other treatments, or in some cases instead of the other treatments. Other studies have shown that high doses of many vitamins help cancer patients regardless of other treatments.
Vigorous exercise can reduce a woman’s risk of breast cancer. In a study of physical activity and risk, it was only vigorous exercise that had a statistically significant effect. Researchers followed 32,269 post-menopausal women for 11 years and found that overall, any physical activity appeared at first analysis to reduce risk, but all of the apparent benefits were attributable to those women in the vigorous exercise category. (Leitzmann MF, et al., Prospective study of physical activity and risk of postmenopausal breast cancer. Breast Cancer Res. 2008 Oct 31;10(5):R92. [Epub ahead of print])
The vigorous exercisers had a 32 percent lower risk of developing breast cancer than those who did the least physical activity. The benefit was limited to those women who had a normal body mass index (BMI) of 25 or less. For those women who exercised but had a higher BMI (over 25), the risk was actually 18 percent higher than baseline.
In a Japanese behavioral study, body weight was influenced by specific eating patterns (as opposed to the content of the diet, which also plays a role). It appears that eating fast and eating until feeling full contributed to being overweight. (Maruyama K, et al., The joint impact on being overweight of self reported behaviours of eating quickly and eating until full: cross sectional survey. BMJ. 2008 Oct 21;337:a2002. doi: 10.1136/ bmj.a2002.)
Researchers observed 3287 men and women aged 30 to 69 and evaluated their eating habits through questionnaires. Eating until full or eating quickly doubled the likelihood that the subject would be overweight. If the participants had both eating habits the risk of high BMI was triple the rate of those with neither habit.
Chocolate is rich in antioxidants, but most of it is highly laced with sugar (and often a number of other highly processed ingredients). For darker chocolates the sugar level is lower, but still significant. One beneficial effect of dark chocolate appears to be a lowering of CRP, the inflammatory marker that is an indicator of cardiovascular risk.
In a study of 4849 subjects, those who consumed dark chocolate regularly had a 1.1 CRP level, while those who were non-consumers had a 1.32 level. This was a significant difference, and put dark-chocolate consumers at a significantly lower risk of heart disease. (di Giuseppe R, et al., Regular consumption of dark chocolate is associated with low serum concentrations of C-reactive protein in a healthy Italian population. J Nutr. 2008 Oct;138(10):1939-45.)
The amount of dark chocolate that provided the benefits was surprisingly small. Those who consumed 20 grams of dark chocolate once every three days had the benefits, but these disappeared with any higher amounts. (A common chocolate bar has 90 grams of chocolate.) This means that consuming just 2/3 of an ounce two to three times a week is enough to get the benefits. (It is not clear whether smaller amounts more frequently would have the same benefits. Also, I recommend only organic chocolate to avoid the pesticide residues that may be in conventional chocolate.)
The problems arise when people choose to consume higher amounts or eat commercial chocolates that are either full of additives or are much higher in sugar and fat. (Typical dark chocolates are 55-80 percent cocoa.) Another problem is the addictive nature of chocolate and sweets in general. If these issues can be overcome, then consuming these small amounts can be a healthy pleasure.
Green tea contains phytochemicals that have numerous health benefits. The most abundant of these substances is a polyphenol called epigallocatechin gallate (EGCG). In an animal study, administration of EGCG helped the immune system and reduced the incidence of diabetes. (Gillespie K, et al., Effects of oral consumption of the green tea polyphenol EGCG in a murine model for human Sjogren's syndrome, an autoimmune disease. Life Sci. 2008 Oct 24;83(17-18):581-8.)
The mice in this study had an animal model of an auto-immune disease (Sjogren’s syndrome), in which glandular secretions are compromised, leading to dry mouth and dry eyes. At 22 weeks, the control animals had significantly more evidence of the immune disorder than those treated with EGCG. The treated animals had healthier salivary glands than the control group.
In addition, treatment with EGCG led to a striking decline in diabetes. These mice are prone to diabetes. After 16 weeks, almost three times as many of the control mice developed diabetes as those fed the EGCG. After 22 weeks, the controls still had a much higher rate of diabetes. One of the effects of EGCG is to reduce inflammation, which is a characteristic of auto-immune diseases.
Eating whole grains can reduce the risk of heart failure. Researchers evaluated 14,153 subjects aged 45 to 64, for an average of 13 years. They examined their dietary habits with a food frequency questionnaire and divided the foods into 7 categories. (Nettleton JA, et al., Incident heart failure is associated with lower whole-grain intake and greater high-fat dairy and egg intake in the Atherosclerosis Risk in Communities (ARIC) Study. J Am Diet Assoc. 2008 Nov;108 (11):1881-7.)
They found that for every daily portion increase of whole grains in the diet heart failure risk was decreased by 7 percent. For each portion of egg in the daily diet, heart failure was increased by 23 percent, and for high-fat dairy products each portion increased the risk by 8 percent.
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