Vitamin Information Center

Long-term supplementation with vitamin E and vitamin C may not prevent cancer, according to data from the Physician’s Health Study II that was presented at the American Association for Cancer Research’s Seventh Annual International Conference in Washington, D.C. on November 16, 2008.[1]

The role of diet in cancer incidence remains a major focus among researchers, as it is becoming more evident that diet may reduce the risk of developing certain types of cancers. For example, vitamin D appears to have a protective effect against pancreatic cancer and also colorectal adenomas.[2][3] In addition, several studies have linked vitamin E, selenium, and lycopene with a reduction in prostate cancer. However, it has also been discovered that supplementation with specific vitamins and minerals often does not have the same protective role as obtaining the nutrients from foods. In other words, there is still much to be learned about the role of nutrients in the prevention of cancer.

The Physician’s Health Study II is a large-scale, long-term, randomized clinical trial involving over 14,000 physicians over the age of 50. The physicians were given either a) 400 IU of vitamin E every other day or placebo or b) 500 mg of vitamin C daily or placebo and were then followed for up to 10 years. The primary endpoint of the vitamin C group was the development of cancer. The primary endpoint of the vitamin E group was the development of prostate cancer, with a secondary endpoint being the development of any type of cancer.

After nearly 10 years of supplementation, there was no evidence that vitamin E or vitamin C played a protective role against cancer. Thus far, there have been 1,929 cancer cases in the group, including 1,013 cases of prostate cancer. The researchers concluded that neither vitamin E nor vitamin C offers any beneficial effect against cancer.

Research in this field is ongoing; however, the results from this study indicate that vitamin supplements may not provide the same benefits as vitamins included as part of a healthy, balanced diet.

References:

[1] Buring JE, Sesso HD, Gaziano JM, et al. A randomized factorial trial of vitamins E and C in the prevention of cancer in men: the Physicians’ Health Study II. Proceedings from American Association for Cancer Research Annual Meeting. Abstract #PR-1.

[2] Skinner HG, Michaud DS, Giovannucci E, Willett WC, Colditz GA, Fuchs CS. Vitamin D Intake and the Risk for Pancreatic Cancer in Two Cohort Studies. Cancer Epidemiology, Biomarkers, and Prevention. 2006;15:1688-95.

[3] Wei MY, Garland CF, Gorham ED. Vitamin D and prevention of colorectal adenoma: A meta-analysis. Cancer Epidemiology, Biomarkers and Prevention. 2008;17(11):2958-2969.

An abundance of vitamin C in the diet may help lower a person’s risk of developing type 2 diabetes, new research suggests.

In a study of middle-aged and older men and women, those with the highest blood levels of vitamin C were significantly less likely to develop diabetes over 12 years than those with the lowest levels, researchers found.

Fruits and vegetables are the main source of vitamin C in Western diets, and blood levels of vitamin C are good markers of fruit and vegetable intake, Dr. Nita G. Forouhi, at the Institute of Metabolic Science at Addenbrooke’s Hospital, Cambridge, England, and colleagues note.

The current findings “re-endorse the public health message of the beneficial effect of increasing total fruit and vegetable intake,” the investigators wrote in Archives of Internal Medicine.

Forouhi’s team followed 21,831 healthy men and women who were 40 to 75 years old for the development of type 2 diabetes. At study entry, all participants provided detailed health and lifestyle information, as well as blood samples, which investigators used to determine vitamin C levels.

Over the course of the study, 423 men and 312 women developed type 2 diabetes, an overall rate of 3.2 percent.

According to the investigators, the likelihood of developing diabetes was 62 percent lower in men and women with the highest circulating vitamin C levels, relative to men and women with the lowest vitamin C levels.

Factoring out other characteristics associated with diabetes risk, such as older age, gender, family history, alcohol intake, physical activity, smoking status and body weight did not significantly alter these associations.

These data offer “persuasive evidence of a beneficial effect of vitamin C and fruit and vegetable intake on diabetes risk,” Forouhi and colleagues conclude.

New research has concluded vitamin K2 consumption can aid recovery from hip fractures as well as have potential osteoporosis benefits.

Published in the European Journal of Epidemiology, Japanese researchers found a positive link between vitamin K2 and hip fractures and osteoporosis, and suggested a review of the, “dietary reference value of vitamin K from the perspective of osteoporosis would be useful.”

The current Japanese reference value is 55mcg for women and 65mcg per day for men. In the US and Canada it is 120mcg per day for men and 90mcg per day for women. In France the limit is 65mcg per day for both men and women.

“Since regions which consumed a lot of vitamin K, especially vitamin K2, showed a low incidence of hip fracture, we considered that vitamin K intake, not absorption, of over 300 mcg/day would be helpful to reduce the incidence of hip fracture,” the researchers concluded.

Family K

The vitamin K family includes the forms phylloquinone (K1) that are typically found in cruciferous vegetables and menaquinone (K2), which are sourced from bacteria. Studies have shown K2 to be the more important nutrient in regard to bone health.

“Menaquinone-7 (K2) showed a very long half-life time compared to vitamin K1,” the researchers wrote. With this in mind they recommended higher doses in regions like Europe and North America, where vitamin K1 consumption is higher.

The study also investigated vitamin D, calcium and magnesium, which have strong clinical bone health backing, and found when these were adjusted for, vitamin K2 continued to reveal a beneficial effect.

Dietary sources

The study assessed population diets in various regions of Japan as well as dietary differences, and found that those regions where certain vitamin K-rich fruits and vegetables were prominent had reduced rates of hip fracture.

“There was also a striking pattern of high intake of vitamin K and low incidence of hip fracture in eastern areas of Japan, with the opposite pattern-a low intake of vegetables rich in vitamin K and a high incidence of hip fracture-in western areas,” they wrote.

“These findings lend support to the idea that vitamin K is an important factor explaining regional differences in the incidence of hip fracture.”

Natto, a food made from fermented soy beans, was singled out as being a particularly abundant vitamin K source.

K for bones

The researchers recognised that the role of Vitamin K role in assisting bone health is relatively new.

“Calcium, the most studied nutrient in the area of bone health, is known for its effectiveness in retarding bone loss in postmenopausal women,” they said. “Magnesium and vitamin D play important roles in calcium and bone metabolism. Vitamin K, originally recognised as a factor required for normal blood coagulation, is beginning to receive more attention for its role in bone metabolism.”

Due to the ecological nature of the study, a “causal linkage between the incidence of hip fracture and intake of vitamin K” could not be confirmed but the researchers said, “further research using more robust epidemiological methods is warranted.”

Estimates suggest that in the absence of primary prevention the number of hip fractures worldwide will increase to approximately 2.6 million by the year 2025, and 4.5 million by the year 2050.

Osteoporosis weakens bone strength which increases the likelihood of hip fracture, a problem that increases with age.