Vitamins have done wonder in our medical history. Vitamin D supplement has made Rickets a rare disease. Folic acid intake by pregnant women have reduced the incidence of spina bifida in newborns. These public health achievements led many of us thinking that if a little is good, then more is better. Some have speculated that antioxidants such as beta-carotene, vitamins A, C and E, may protect human cells from premature degradation. Thus, they may prevent or even cure cancers. Not surprisingly, many of us jump into conclusion of taking multivitamins is good for our health.
However, the science of vitamins is not very clear. The Women's health initiative study which followed 160,000 women for about 8 years showed that 42% of study subjects who took multivitamins suffered the same rates of cancers, heart attacks, and strokes as the study participants who did not take the multivitamins. A trial showed concerning increased rate of lung cancer in patients who took beta-carotene and other supplements. A randomized trial of 30,000 men was halted in 2008 when preliminary analysis of the study showed that selenium and Vit E supplements were increasing number of cancers.
From Uptodate, I found this statement: The US Preventive Services Task Force (USPSTF) clinical practice guideline provides several recommendations for vitamin supplementation and can be accessed through the website for the Agency for Healthcare Research and Quality at www.ahrq.gov/clinic/uspstfix.htm. The USPSTF recommends 400 to 800 micrograms/day Folic acid for all women planning of pregnancy. The USPSTF found insufficient evidence to recommend for or against the use of supplements of vitamins A, C, E, multivitamins with folate, or antioxidant combinations for the prevention of cancer or cardiovascular disease. The USPSTF also recommend against the use of beta carotene for the prevention of cancer or cardiovascular disease.
What shall we do? My suggestion is we should follow the USDA's dietary guidelines: for most of us, our vitamins should come from our foods rather than vitamin supplements. Our meals should consists of wide variety of fruits, vegetables and even some proteins (lean meat). I usually tell my patients that their meals should have variety of colors and variation. Foods are very complex with many undiscovered biologically active ingredients and we have evolved for many millions years adapting to them. A few single vitamins, recently discovered, are too simple solution to meet our dietary needs.
Reference:
However, the science of vitamins is not very clear. The Women's health initiative study which followed 160,000 women for about 8 years showed that 42% of study subjects who took multivitamins suffered the same rates of cancers, heart attacks, and strokes as the study participants who did not take the multivitamins. A trial showed concerning increased rate of lung cancer in patients who took beta-carotene and other supplements. A randomized trial of 30,000 men was halted in 2008 when preliminary analysis of the study showed that selenium and Vit E supplements were increasing number of cancers.
From Uptodate, I found this statement: The US Preventive Services Task Force (USPSTF) clinical practice guideline provides several recommendations for vitamin supplementation and can be accessed through the website for the Agency for Healthcare Research and Quality at www.ahrq.gov/clinic/uspstfix.htm. The USPSTF recommends 400 to 800 micrograms/day Folic acid for all women planning of pregnancy. The USPSTF found insufficient evidence to recommend for or against the use of supplements of vitamins A, C, E, multivitamins with folate, or antioxidant combinations for the prevention of cancer or cardiovascular disease. The USPSTF also recommend against the use of beta carotene for the prevention of cancer or cardiovascular disease.
What shall we do? My suggestion is we should follow the USDA's dietary guidelines: for most of us, our vitamins should come from our foods rather than vitamin supplements. Our meals should consists of wide variety of fruits, vegetables and even some proteins (lean meat). I usually tell my patients that their meals should have variety of colors and variation. Foods are very complex with many undiscovered biologically active ingredients and we have evolved for many millions years adapting to them. A few single vitamins, recently discovered, are too simple solution to meet our dietary needs.
Reference:
- U.S. Preventive Services Task Force. Ann Intern Med. 2009;150(9):626
-Routine vitamin supplementation to prevent cancer and cardiovascular disease: recommendations and rationale.Ann Intern Med. 2003;139(1):51
- Uptodate. Vitamin supplementation. November 2012
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