Vitamin B6 for Colon Cancer: Another Potential Benefit from This Critical Nutrient

Résultat de recherche d'images pour "Colon Cancer"Last year, researchers in Scotland demonstrated that increased blood levels of vitamin B6’s active form, pyridoxal 5´-phosphate (PLP), were correlated with a decreased incidence of colorectal cancer. (Theodoratou E, et al. Dietary vitamin B6 intake and the risk of colorectal cancer. Cancer Epidemiol Biomarkers Prev.;17[1]:171-82)

This year, scientists at Brigham and Women’s Hospital and Harvard Medical School showed similar results in a prospective study that involved nearly 15,000 people. (Lee J, et al. Prospective study of plasma vitamin B6 and risk of colorectal cancer in men. Cancer Epidimiol Biomarkers Prev. 18[4]:1197-1202)

These studies suggest that increased intake of vitamin B6 may decrease the risk for acquiring colorectal cancer—a disease that accounts for nearly 500,000 deaths worldwide every year—by as much as 50%.

Since vitamin B6 in its several forms (pyridoxine, pyridoxal, and pyridoxamine) is not present in high amounts in many foods, and since it is lost in cooking and in the refining of foodstuffs, B6 is not the easiest vitamin to obtain in high amounts from food sources. (Elson M Haas. Staying Healthy with Nutrition: Vitamin B6 (Pyridoxine). Celestial Arts, 121-124)

And, because many Americans eat a lot of processed foods, the average U.S. citizen may be missing the anti-cancer benefits conferred by higher levels of PLP in the bloodstream.

How Does Vitamin B6 Protect Us from Colon Cancer?

While the precise anti-cancer mechanism of vitamin B6 has yet to be described (the vitamin manifests its influence in protean ways) the anti-inflammatory and free-radical scavenging actions of PLP may play a role.

Harvard researchers found a positive correlation between blood levels of PLP and blood levels of folic acid and cobalamin, two other B vitamins. Further, PLP levels are inversely correlated with homocysteine, C-reactive protein, tumor necrosis factor-alpha, and interleukin-6, all of which are inflammatory molecules or markers for inflammation.

Thus, higher intake of vitamin B6 leads to higher blood levels of its active form, PLP, which is in turn associated with lower levels of inflammatory molecules. Although this might seem serendipitous at first, these associations become clearer when one understands that PLP plays a vital role as a coenzyme in metabolizing harmful inflammatory molecules, such as homocysteine, to less toxic substances.

It is intriguing that the majority of colon cancers express the cyclooxygenase-2 (COX-2) enzyme, which is not only instrumental in helping the cancer to grow and metastasize, but is also responsible for creating a variety of prostaglandins and other inflammatory molecules.

What are Good Food Sources of Vitamin B6?

While vitamin B6 is widely available in nature, not many foods contain high levels. Nor is this vitamin replaced in enriched flour products.

  • Meats, particularly organ meats (e.g., liver and heart), and whole grains are the best sources of vitamin B6. Wheat germ is one of the richest sources.
  • Since vitamin B6 is vital for the formation and metabolism of proteins, other protein-rich foods contain reasonably good levels, too: peanuts, walnuts, eggs, fish, poultry, and legumes are all good sources.
  • Raw sugar cane and unrefined sugar contain some vitamin B6, but refined sugar has none.
  • Good vegetable and fruit sources include collard and mustard greens, bell peppers (ripened), cabbage, cauliflower, avocados, spinach, potatoes, garlic, turnips, prunes and bananas.
  • Mushrooms also contain vitamin B6.

Supplementation with Vitamin B6 and Recommended Daily Intakes

Needs for vitamin B6 change in a variety of situations. Higher protein intake necessitates a higher dosage; stress, hormonal status, alcohol consumption, pregnancy, illness, and other variables also increase one’s need for PLP.

In general, 10 – 15 mg of vitamin B6 daily is a quite reasonable adult dose (since B6 is a water-soluble vitamin, fairly large doses can be tolerated without any ill effects in most individuals). Doses up to 1,000 mg daily can be tolerated for short periods of time (a few weeks), and many people supplement with 500 mg daily on an ongoing basis.

Vitamin B6 should be taken with other B vitamins and adequate magnesium to avoid imbalance and provide optimal benefit.

The National Academy of Sciences established age-related, daily Recommended Dietary Allowances (RDAs) for vitamin B6:

  • Infants, 0 – 6 months 100 mcg
  • Infants, 7 – 12 months 300 mcg
  • Children, 1 – 3 years 500 mcg
  • Children, 4 – 8 years 600 mcg
  • Males, 9 – 13 years 1.0 mg
  • Males, 14 – 50 years 1.3 mg
  • Males, over 50 years 1.5 mg
  • Females, 9 – 13 years 1.0 mg
  • Females, 14 – 50 years 1.2 mg
  • Females, over 50 years 1.5 mg
  • Pregnant women, any age 1.9 mg
  • Lactating women 2.0 mg

Some scientists have long questioned whether these recommendations were high enough. Given the information that higher blood levels of PLP, B6’s active coenzyme form, may prevent colon cancer, it is possible that new RDAs will be forthcoming.

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