May 29, 2007 – Increasing the daily intake of vitamin D could help reduce the number of cases of colorectal cancer in the population, say American researchers.
The results of an analysis1 five studies conducted between 1989 and 2006 indicate that a daily intake of 1000 IU to 2000 IU (25 mcg to 50 mcg) of vitamin D3 (cholecalciferol) is to reduce the risk for this cancer.
The University of California team compared vitamin D levels in the blood of 1,448 subjects, including 535 people with colorectal cancer. According to the results, the number of people with this type of cancer decreases as the amount of vitamin D in the blood increases.
The authors of the study believe that the low intake of vitamin D may well be related to the high number of colorectal cancer in the West.
It does appear that the chances of contracting colon cancer are higher in areas of the world where people are less exposed to natural light. Regular sun exposure would prevent the growth of cancer cells in the colon and substantially reduce the mortality associated with colon cancer2. It is believed that the protective effect is due to the mechanism by which the sun causes the production of vitamin D.
The vitamin D debate
These results have fueled the debate that has been going on for several years around the intake considered sufficient.3 in vitamin D.
This intake varies from 200 IU (5 µg) to 600 IU (15 µg), depending on age. (See table below). Maximum tolerable intakes4 are estimated at 1000 IU (25 µg) for infants up to six months, and 2000 IU (50 µg) for the rest of the population.
Some researchers also suggest that a daily dose of 4000 IU (100 µg) is quite safe. The National Academy of Sciences (United States) estimated, as early as 1997, that a daily dose of 2000 IU was safe, even reporting that daily dosages of 3800 IU did not cause any toxicity.
Adequate intake of vitamin D
age |
µg |
UI |
from 0 to 50 years old |
5 µg |
200 IU |
from 51 to 70 years old |
10 µg |
400 IU |
over 70 years |
15 µg |
600 IU |
Pierre Lefrançois – PasseportSanté.net
1. Gorham ED, Garland CF, et al. Optimal vitamin D status for colorectal cancer prevention: a quantitative meta analysis. Am J Prev Med. 2007 Mar; 32 (3): 210-6.
2. See our Colorectal Cancer fact sheet on this subject.
3. In the absence of sufficient scientific data, the Canadian and American authorities have set, not a recommended nutritional intake (RDA), but a sufficient intake (AS). SA is based on estimated average intakes in healthy North Americans.
4. Maximum amount of a nutrient that the majority of the population can ingest continuously without risking adverse health effects.