Benefits Outweigh Risks
The recent review of vitamin D for cancer prevention (1) was based on the IARC review [Ref. 6 in (1)]. My critical review of the IARC review pointed out that the evidence for beneficial effects of solar UVB and vitamin D was much stronger than concluded in the review (2).
Ecological studies (epidemiological studies researching disease outcome and risk-modifying factors averaged by geographical region) are better for studying the effects of UVB and vitamin D in reducing the risk of cancer than observational studies and randomized controlled trials (RCTs) for several reasons:
- solar UVB is the primary source of vitamin D for most people
- there is a long lag time between cancer initiation and detection or death
- RCTs and observational studies often use too little vitamin D
- too short a time period, and too few people.
An ecological study for Spain illustrates this. The two factors used for vitamin D were nonmelanoma skin cancer (NMSC) mortality rate and latitude, for 48 provinces. NMSC was inversely correlated and/or latitude directly correlated with mortality rates for 15 types of cancer after adjustment for lung cancer mortality rates, included to account for the effect of smoking (3). Death rates were much higher for internal cancers than for NMSC.
William B. Grant, Ph.D.
Sunlight, Nutrition, and Health Research Center (SUNARC)
P.O. Box 641603
San Francisco, CA 94164–1603, USA
Conflict of interest statement
The author receives or has received funding from the UV Foundation
(McLean, VA), the Sunlight Research Forum (Veldhoven), Bio-Tech-Pharmacal (Fayetteville, AR), and the Vitamin D Council (San Luis Obispo, CA), and the Danish Sunbed Federation (Middelfart, Denmark).
1: 25–33. MEDLINE
|1.||Zeeb H, Greinert R. The role of vitamin D in cancer prevention: Does UV protection conflict with the need to raise low levels of vitamin D? Dtsch Arztebl Int 2010; 107(37): 638–43. VOLLTEXT|
|2.||Grant WB: A critical review of vitamin D and cancer: a report of the IARC Working Group on vitamin D. Dermato-Endocrinology 2009;|
1: 25–33. MEDLINE
|3.||Grant WB: An ecologic study of cancer mortality rates in Spain with respect to indices of solar UV irradiance and smoking. Int J Cancer 2007; 120: 1123–7. MEDLINE|