The Vitamin D Debate

Vitamin D is quite the popular nutrient these days.

We know most Americans have blood vitamin D concentrations low enough to be considered insufficient or deficient. The cause is two-fold.

  • Most people eat less than the recommended 600 IU of vitamin D per day. It’s difficult to receive this amount of vitamin D through food alone, particularly if you do not regularly consume milk/dairy or fatty fish.

  • Vitamin D is also manufactured by our skin when we’re exposed to sunlight, but most people do not receive adequate sun exposure. 15 minutes of sun exposure is enough to fill vitamin D stores, but we must also consider the risk of skin cancer. For those at risk for skin cancer, those that wear sunscreen or stay indoors regularly, and those with dark pigmented skin, food or supplemental vitamin D may be necessary.

Since vitamin D deficiency has been recognized as a problem among most Americans – children and adults of all races and ethnicity – a lot of research has been conducted to understand how this deficiency might cause chronic disease, like cancer.

NCI has gathered evidence on vitamin D and cancer. Some of the first studies suggested those who live in southern latitudes have a lower risk of cancer, prompting the belief that more sunlight exposure = higher vitamin D levels = lower cancer risk. Other studies have suggested those with higher vitamin D levels, regardless of where they live, have a lower risk of cancer, possibly because vitamin D slows or prevents the development of cancer.

But, no studies have examined the impact of dietary vitamin D on actually developing cancer, so we cannot make any accurate conclusions about the relationship between the two. The latest study, published in Lancet on January 24, looked at all of the evidence on vitamin D and suggests vitamin D intake (with or without calcium), does not lower the risk of any chronic condition, including cancer, by more than 15%.

This conclusion has made headlines and is another example of the difficulty of nutrition research. We are always looking for a magic pill or nutrient, a simple and easy way to prevent and treat disease. Instead, it’s more and more evident that we are complex human beings and an easy fix is unrealistic.

So. What can we take away from the vitamin D debate?

  • Making sure we meet vitamin D recommendations for age and gender will certainly not hurt
  • If you do not regularly eat foods containing vitamin D, but spend time outside each day, you probably do not need a vitamin D supplement.
  • If you are not outside regularly, and do not eat vitamin-D containing foods, you may benefit from a vitamin D and/or calcium supplement to improve overall health.
  • The debate is still on about whether vitamin D impacts cancer development, treatment, or recovery.
  • Instead of focusing on single or combinations of nutrients, focus on improving your overall diet during treatment and recovery.
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