Vitamins

Many people think taking lots of vitamins can be beneficial to our body’s health. This is not necessarily true. Several clinical studies have shown harmful effects of excessive vitamins.

 

Vitamin B6:
Many studies on association of vitamin B6 and colon cancer have yielded inconsistent results.

• A recent meta-analysis of nine studies showed low vitamin B6 intake and blood pyridoxal 5'-phosphate (PLP; the active form of vitamin B6) levels were associated with higher risk of colorectal cancer.
  
• However, this analysis requires further prospective study for confirmation.

 

Vitamin B12 and folic acid:

• For example, the recent publication in the Journal of American Medical Association (JAMA, November 18th 2009) of two studies performed in Norway showed that patients who take regular vitamin B12 or folic acid supplement had higher incidence of cancer and increased risk of all-cause mortality.

 

Vitamin D:

• Though other vitamins have been found to be unhelpful for long-term use, vitamin D is in a different category and its deficiency has been shown to be associated with a greater risk of developing cardiovascular disease for those with hypertension, according to a new finding from researchers with the Framingham Heart Study.
• It has also been found that many women with breast cancer have low vitamin D levels in their blood.
• Some studies even suggest that lack of vitamin D may be associated with increased risk of cancer relapse.
• Adequate vitamin D intake may help prevent breast cancer.
• There is some evidence suggesting that this protection is especially good for women who are exposed to sunlight and have higher dietary intake of sources of vitamin D during adolescence.

 

Checking vitamin D serum level can tell you if you have lower than the normal level and you may consider taking vitamin D supplement if it is low.

 

Vitamin D production requires sunlight and the function of kidneys and liver. In scientific research it has been shown that vitamin D helps cells to develop and grow appropriately.

 

However, caution needs to be taken and taking excessive vitamin D is not advised.

• You need to discuss the dosage with your doctor.
• Too much vitamin D can cause high blood calcium and lead to hypervitaminosis D, a serious but treatable medical condition.

 

The Institute of Medicine recommends that:

• Children and adults up to age of 50 receive 200 international units of vitamin D daily.
• Adults older than 50 is 400 to 600 units daily.
• However, many experts feel these recommended dosages too low.
• The American Academy of Pediatrics now recommends children and adolescents get 400 units a day.

Many experts even recommend that adults get as much as 1000 to 2000 units a day.

 

Vitamin E:

• Long-term vitamin E supplement is also not beneficial.
• A study (JAMA, March 16th 2005) showed that long-term vitamin E supplement in patients with diabetes or vascular disease not only did not improve cancer or major cardiovascular events but may increase the risk for heart failure. 

 

Selenium:
Selenium has been shown in a large study not to prevent prostate cancer, nor did vitamin E.  From a large clinical trial called SELECT, the following key points were drawn:

• SELECT stands for the Selenium and Vitamin E Cancer Prevention Trial, a prevention clinical trial to see if one or both of these dietary supplements prevent prostate cancer.
• SELECT is continuing to evaluate the effects of the supplements but participants are no longer taking study supplements.
• The independent Data and Safety Monitoring Committee for the trial found that selenium and vitamin E, taken alone or together for an average of five and one-half years, did not prevent prostate cancer.
• The SELECT data showed two concerning, but not statistically significant, trends:
• there were slightly more cases of prostate cancer in men taking only vitamin E and
• slightly more cases of diabetes in men taking only selenium.
• Neither of these findings proves an increased risk from the supplements and may be due to chance.