Vitamin D is the name of a group of fat-soluble prohormones (substances that normally have little hormonal activity but can be converted into hormones by the body).
Vitamin D helps the body use calcium and phosphorus to build healthy bones and teeth.
Skin exposed to sunlight can produce vitamin D, and vitamin D can also be obtained from certain foods.
Vitamin D deficiency can cause bone loss called rickets in children and osteomalacia in adults.
The two main forms of vitamin D that are important for humans are vitamin D2, or ergocalciferol, and vitamin D3, or cholecalciferol. Most people get at least some of the vitamin D they need from sun exposure.
Food sources include some foods that naturally contain vitamin D, such as oily fish, fish liver oil, and eggs.
Why are cancer researchers investigating the possible link between vitamin D and cancer risk?
Early epidemiological studies have shown that morbidity and mortality from some types of cancer are lower in people living in southern latitudes, where solar radiation is relatively high, than in people living in northern latitudes.
Because exposure to ultraviolet light from sunlight causes vitamin D production, the researchers suggest that fluctuations in vitamin D levels might explain this relationship.
However, more research is needed based on more robust studies to determine whether higher vitamin D levels are associated with lower cancer morbidity or mortality.
Experimental evidence also suggests a possible link between vitamin D and cancer risk.
Studies on cancer cells and tumors in mice have shown that vitamin D has several effects that can slow or prevent cancer progression, including promoting cell differentiation, reducing cancer cell growth, stimulating cell death (apoptosis) and blood vessel formation (angiogenesis).
What is the evidence that vitamin D can help reduce cancer risk in humans?
A number of epidemiological studies have examined whether people with higher intakes of vitamin D or blood levels of vitamin D have a lower risk of developing certain types of cancer.
The results of this study are contradictory, perhaps because of the challenges in conducting such research.
For example, dietary studies do not take into account the vitamin D produced in the skin from sun exposure, and vitamin D levels measured in the blood at any given time (as in most studies) may not reflect a person’s actual vitamin D level.
stand up. . . It’s also possible that people with higher intakes of vitamin D or blood levels have other healthy behaviours.
Perhaps one of these behaviours, in addition to taking vitamin D, affects cancer risk.
Several randomized trials of vitamin D have been conducted, but these were designed to evaluate bone health or other non-cancerous outcomes.
Although some of these studies provide information on cancer incidence and mortality, their results need to be confirmed by additional studies because these studies were not designed to investigate cancer.
The most common types of cancer in humans are colon cancer, breast cancer, prostate cancer, and pancreatic cancer.
A number of epidemiological studies have shown that higher vitamin D intake or blood levels are associated with a reduced risk of colorectal cancer (7-10).
In contrast, a randomized study by the Women’s Health Initiative found that healthy women who took vitamin D and calcium supplements for an average of 7 years had no reduced incidence of colorectal cancer (11).
Several investigators have suggested that the relatively small amount of vitamin D supplementation (10 g or 400 IU, once daily), the participants’ ability to ingest vitamin D supplements themselves, and the brief follow-up of participants in the study may explain why the decreased risk of colorectal cancer was noted.
The evidence for an association between vitamin D and the risk of all other malignancies studied is inconclusive.
