SEVERAL MEASURES OF IRON STATUS SHOW A SIGNIFICANT INVERSE ASSOCIATION WITH COLORECTAL CANCER

As part of the Alpha-tocopherol, beta-carotene cancer prevention (ATBC) study, a randomized, double-blinded, placebo-controlled 2 x 2 factorial design, researchers simultaneously assessed dietary iron, supplemental iron and serum markers of iron status relative to colorectal cancer risk.  Previous epidemiological studies have implicated red meat, possibly because of increased iron intake by higher meat consumers, as a risk factor, but no single study has simultaneously assessed all the factors.  Colorectal cases in 130 individuals qualified for analysis.  There were only two notable baseline differences between cases and controls: 6% of cases reported ever using daily aspirin compared to 20% of the controls, and mean serum C-reactive protein (CRP) was 30% higher in cases. Both controls and cases showed dietary and serum iron measures in the normal range. Serum iron indices did not correlate with dietary iron intake but supplemental iron intake correlated with serum iron and transferrin saturation.  Above average consumers of red meat showed higher serum ferritin levels.

Relative to colorectal cancer risk, results showed the suggestion of an inverse association with dietary iron and a significant inverse association with serum ferritin. The highest quartiles of serum ferritin, serum iron and transferrin saturation, compared to the lowest, were inversely associated with colon cancer risk. The only association with an elevated risk of colon cancer was serum unsaturated iron binding capacity (UIBC).  There was no association between any of the measured iron indices and rectal cancer.

There have been conflicting findings with regard to dietary iron and colorectal cancer risk: studies have reported no association and positive associations. This study found no correlation between dietary iron (or intake of meat) and iron stores. It should also be noted that in this ATBC study of Finnish males, no association was found for red meat as a risk factor for colorectal cancer. The authors suggest that several mechanisms could explain the significant inverse associations. In cases, low serum iron indices may be due to less iron being absorbed leaving more iron present in the gastrointestinal tract where damage may occur. Since 60% of newly diagnosed colorectal cancer cases show signs of iron deficiency, this may be evidence of the iron needs for tumor growth. There continues to be controversy about the effect of dietary iron on iron stores and iron intake on colorectal cancer risk. This study, however, found a significant inverse association between many serum iron indices and colon cancer risk.

Citation:
LIron and colorectal cancer risk in the alpha-tocopherol, beta-carotene cancer prevention study. Cross AJ, Gunter MJ, Wood RJ, Pietinen P, Taylor PR, Virtamo J, Albanes D, Sinha R. International Journal of Cancer.2006 Jan 19.

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Iron and colorectal cancer risk in the alpha-tocopherol, beta-carotene cancer prevention study

WALL STREET JOURNAL REPORT QUESTIONS EFFICACY OF DIETARY SUPPLEMENTS

The March 20, 2006 edition of the Wall Street Journal included a comprehensive report on vitamin supplementation by Health Journal columnist, Tara Parker-Pope.  For years dietitians have heralded "food first" as the best insurance for meeting dietary needs for micronutrients.  The WSJ report, "The Case Against Vitamins," not only reiterates that advice, it also suggests that some supplemental vitamin intake may cause harm. Highlights from Ms. Parker-Pope's report include:

• There is controversy on the role of free radicals in the body, which, some suggest, may serve to alert the body's immune system.  As increased intakes of antioxidants remove free radicals from the body, the immune system may not be alerted to repair damage, thus allowing disease to set in.

• High doses of antioxidants may be detrimental.  In test tubes, high doses of a single antioxidant can become a pro-oxidant, meaning they start to oxidize and create free radicals.

• Recent studies on higher intakes of vitamin E supplements (greater than 400 IUs) showed disappointing results including a 4-6% increase for risk of dying and a 13% higher risk for heart failure. Vitamin E supplementation during cancer treatment showed 30% reduction in side effects but a 37% increase in the rate of cancer recurrence.

• Although an association has been shown between diets rich in beta carotene and vitamin A with low cancer risk, supplements may be risky. Smokers taking 20mg daily of beta carotene showed an 18% higher rate of lung cancer. Another study among smokers and workers exposed to asbestos found a 28% higher rate for lung cancer and a 26% higher rate for death from heart disease for those taking combined vitamin A / beta carotene therapy. Vitamin A intake has also been shown to negatively impact the risk for hip fractures. In this study, dietary Vitamin A intake was also implicated which suggests that possibly too many foods are fortified with vitamin A.

• Twenty-three studies have not proven the benefit of vitamin C intake to prevent colds. Vitamin C has been shown to reduce colds by 50% for individuals exposed to extreme physical stress, but the benefits have not been replicated among the general population. Other studies have suggested that Vitamin C supplementation may slightly increase the risk of dying among elderly people. Recent research has shown that Vitamin C feeds cancer cells more rapidly than normal cells so vitamin C may actually protect tumors. In 2001, scientists showed that vitamin C intake may make cancer cells resistant to chemotherapy.

• A recent study suggests that supplementation with folic acid, vitamin B₁₂ and vitamin B₆ does not reduce the risk for heart attacks among patients with established heart disease. Their efficacy for healthy people remains undetermined. However, all scientific evidence continues to support the role of maternal folic acid in reducing the risk for neural-tube defects in babies.

• There is controversy on the role of calcium and vitamin D in reducing hip-fractures in women over 60. However, calcium supplementation may increase the risk for kidney stones. Medical advice still maintains the need for vitamin D supplementation among elderly people who drink little milk and have minimal exposure to sunlight.

• Though doctors may still advise a daily multivitamin, recent evidence found that multivitamin supplementation for a year did not decrease medical office visits or rates of infection among elderly people.

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