VITAMIN D

What May Be The Benefit Of Giving Supplements Of Vitamin D To The Elderly?

What May Be The Benefit Of Giving Supplements Of Vitamin D To The Elderly?

Introduction

There is mounting evidence that vitamin D reduces the risk of cancer and increases the rate of survival in elderly people. The evidence includes results of observational studies, including ecologic, case-control, and cohort; laboratory studies using cancer cells; and animal studies. There are 22 cancers that appear to be more likely to occur in people who are deficient in vitamin D or have limited solar ultraviolet B (UVB) exposure. (Cui and Rohan, 2005, 14-27) Dose-response relationships have been delineated cancers of the colon and breast. Despite these findings, there is only limited acknowledgement at the national policy level that solar UVB (290-315 nm) and vitamin D reduce the risk of many common cancers, and vitamin D recommendations do not yet reflect the findings that 1000-2000 IU/day of vitamin D3 is needed, which is several times the recommended daily allowance, of about 400 IU/day, to reduce incidence of colon and breast cancer by 33-50 percent.

Observational Studies

The concept that vitamin D reduces the risk of cancer was originally proposed by Cedric and Frank Garland in 1980 after they observed the geographic variation of colon cancer mortality rates in the United States for the period 1950-69 and noted that the mortality rates were much lower in the southwest than in the northeast. The inverse correlation with annual sunlight hours was easily demonstrated; identifying vitamin D as the cancer-prevention agent was based on realizing that vitamin D production is the most important physiological effect of solar irradiation. This hypothesis gained support when the researchers were later able to show that risk of colorectal cancer was inversely correlated with oral vitamin D intake and serum 25-hydroxyvitamin D (calcidiol) levels. Subsequently, the Garlands added breast and ovarian cancer to the list of vitamin D-sensitive cancers via ecologic studies in Canada, the United States, and the former Soviet Union, and Gary Schwartz and coworkers added prostate cancer to the list through an ecologic study in the United States.

It was not until quite recently that many more cancers were identified as being vitamin D sensitive. When the Cancer Atlas for the U.S. was updated in 1999 to incorporate data from the period 1970-94, William Grant noticed that many cancers had geographic distributions similar to those for breast, colon, ovarian, and, to a lesser extent, prostate cancer. He was also aware of the July 1992 solar UVB dose map for the United States, developed using data from a NASA satellite instrument, the Total Ozone Mapping Spectrometer (TOMS). Solar UVB has an asymmetrical geographic variation in the United States, with UVB dose contours east of the Rocky Mountains shifted about 400 miles south of those to the west because of two factors: first, surface elevations are generally higher in the west, thereby producing less atmospheric attenuation of solar UVB; and second, the stratospheric ozone layer is thinner in the west because the prevailing westerly ...