Beta carotene and vitamin B12 are both common antioxidants. The National Cancer Institute notes that antioxidants are thought to help in the treatment and prevention of certain cancers; however, some studies suggest that these substances are either ineffective against lung cancer, or actually speed its rate of growth. For example, the 1994 results of a study involving male smokers in Finland found that beta carotene significantly increased incidents of lung cancer.
Beta Carotene and Lung Cancer in Smokers
The prevention trial conducted by the National Institute for Health and Welfare of Finland, along with the United States National Cancer Institute, studied the effects of beta carotene in subjects from 1985 to 1993. A total of 29,100 male smokers took supplements during this time, and were observed after the trial to record the long-term effects. The significant increase in lung cancer occurrences among subjects who took beta carotene suggested a causal link between beta carotene supplements and lung cancer. Researchers went on to comment that it was conceivable that the dose used in the study was too low, but that this was unlikely since the dose was much higher than average dietary levels.
Beta Carotene for Nonsmokers
Research cited by Dole indicates that beta carotene lowers the risk of all cancers in subjects who have never smoked. In these studies, the beneficial preventive effects of beta carotene supplements surpassed those of average dietary consumption. However, as with the Finland study, former and current users of tobacco were significantly more likely to develop tobacco-related cancers, including lung cancer, due to supplemental beta carotene intake. For former smokers, these results indicated that supplements were not recommended.
Dietary Beta Carotene vs. Supplements
In a Dutch study, dietary beta carotene intake was found to reduce mortality overall, extending both quantity and quality of life and preventing a number of fatal conditions, which include cancer, according to Dole. This study analyzed 1,100 elderly subjects and found that those with the highest plasma concentrations of alpha carotene and beta carotene had a lower risk of dying from cancer. These findings also adjusted for past smoking, although the research did not produce results pertaining to current smokers. Similar epidemiological studies, which showed an inverse association between lung cancer and carotene-rich food consumption, were referenced in the Finland study, which indicated that beta carotene supplements increased the risk of lung cancer while dietary intake decreased the risk in nonsmokers and former smokers.
Vitamin B12 and Lung Cancer
MayoClinic.com cites preliminary evidence that suggests no connection, either positive or negative, between vitamin B12 and lung cancer. However, vitamin B12 deficiency is a common occurrence in patients suffering from other cancers, including breast cancer. Because of this, researchers hypothesized that vitamin B12 deficiency may result in lower availability of folate, which ensures healthy DNA reproduction and repair. So, higher dietary folate intake tends to be associated with a reduced risk of other cancers, and the proper functioning of your DNA is integral to preventing all cancers.
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