Does it make sense to take vitamin D supplements?
The benefits of vitamin D supplements are controversial. Japanese researchers have now found that vitamin D appears to protect the body from cancer. This leads to the question of whether food supplements with vitamin D are useful in the sense of cancer prevention.
Scientists at the Center for Public Health Sciences at the National Cancer Center in Tokyo found that vitamin D appears to protect against cancer. The doctors published the results of their study in the English-language journal "British Medical Journal" (BMJ).
How does vitamin D get into the body?
Vitamin D plays an important role in the body, the vitamin protects, for example, bones and muscles and prevents diseases such as rickets. Vitamin D is produced when human skin is exposed to sunlight. It can also be ingested with certain foods, such as eggs and oily fish. It is also possible to take vitamin D in food supplements.
Vitamin D protects against liver cancer
The Japanese researchers say that higher levels of the vitamin are associated with a lower risk of cancer, especially liver cancer. Vitamin D also has a weak effect on several types of cancer, explains study author Taiki Yamaji from the National Cancer Center in Tokyo.
Doctors analyzed blood samples from more than 30,000 subjects
This was not the first study to suggest that people with low levels of vitamin D may have an increased risk of a range of cancers. However, the results are not clear, as some studies have found no such effect and other protective effects against certain types of cancer are suspected. The current study looked at this problem. The team examined the levels of the biologically active form of vitamin D in blood samples from more than 30,000 middle-aged people in health centers across Japan during the early 1990s. The study participants were medically monitored over a median of 16 years. The researchers based their analysis on the data from a total of 3,301 participants who developed cancer after registering for the study. In addition, a further 4,044 randomly selected participants were selected for the examination, of whom 450 had cancer.
Vitamin D lowers the risk of cancer
Taking factors such as age, gender, smoking and family history of cancer as well as seasonal differences in circulating vitamin D into account, the team found that higher circulating levels of vitamin D in the blood were associated with a lower risk of cancer. Compared to the quartile of the participants with the lowest circulating vitamin D levels, the quartile with the highest levels had a 22 percent lower risk of cancer. The experts explain that there is no difference in the effects of vitamin D based on gender.
What types of cancer does vitamin D protect against?
When investigating certain types of cancer, the Japanese research team found that the group with the highest levels of vitamin D had a risk of liver cancer reduced by around 50 percent compared to the lowest levels. A weaker effect was also found in so-called premenopausal breast cancer, but there was no clear impact on other types of cancer, including lung cancer, colon cancer, prostate cancer or breast cancer
Were there any restrictions in the study?
The authors point out that the study is subject to restrictions, for example because vitamin D was only taken at certain times. In addition, the participants may simply have been more health conscious than the general public.
The overall cancer risk was reduced
The team found that there was a link to lower overall cancer risk even when liver cancer was excluded from the analysis. The reason for this could be that smaller effects of vitamin D on other types of cancer could add up when viewed together, explains Yamaji.
The protective effect is probably quite modest
The results of the current study are in agreement with other studies, which also found a protective effect of vitamin D against cancer deaths. However, the effect of vitamin D is probably relatively modest and the aim is to avoid a low level rather than to reach high levels, the researchers conclude.
Are the sun's rays enough to get enough vitamin D?
Critics of the study claim that the study does not clearly demonstrate whether a lack of vitamin D has a direct impact on cancer risk or whether this risk is due to poor health. People should simply enjoy the sun and be careful not to get sunburned, this should be enough to get enough vitamin D in summer and to avoid a vitamin D deficiency. (as)