We all know that vitamin D is essential for strong and healthy bones. However, vitamin D has recently been associated with a number of diseases such as cancer, diabetes and heart diseases. Many studies are conducted and presented on the protective effect of vitamin D from these diseases. However, these studies give contradictory results and cause confusion on this issue. That’s why, in this article, we wanted to bring you evidence-based, reliable information about vitamin D and its effect on cancer prevention.
What is vitamin D, what are its functions?
vitamin D; It is a vitamin that increases the absorption of calcium and phosphate minerals from the intestines, provides the necessary mineralization in the bones and is necessary for the growth, strengthening and remodeling of the bones. It is an indispensable compound for strong bones and teeth. If there is not enough vitamin D, bones become thin and fragile, deformities are seen. In addition, vitamin D strengthens the immune system, regulates cell growth, protects the body against muscle weakness, and reduces inflammation. It is also necessary for the regulation of heartbeat, thyroid function and normal blood clotting.
What are the sources of vitamin D?
People can produce vitamin D in their own skin through exposure to the sun, as well as from certain foods or vitamin supplements. When ultraviolet rays from the sun hit the skin, it triggers the synthesis of vitamin D. Daily requirement of vitamin D; Although it can be met by exposing the arms, legs and face to sunlight for 20-30 minutes in general, the amount of sunlight required; It depends on the time of the day and the year, the person’s age, skin color, location, clothing, whether they use sunscreen and other medical problems, if any. In addition to being a good source of vitamin D, the sun not only causes skin burns but also poses a serious risk for skin cancer with the ultraviolet rays it emits. Studies have not yet determined the safe amount of sunlight to protect against skin cancer. However, exposure to sunlight should be limited, and care should be taken especially at noon and summer months when the sun’s rays come at the steepest angles.
Vitamin D is naturally found in many foods. Cod liver oil is high in fatty fish such as sardines and salmon; Green leafy vegetables and egg yolks also contain small amounts of vitamin D. In some countries, milk and dairy products, bread and cereals are enriched with vitamin D, but there is no such practice in our country yet.
Vitamin D, which is obtained from sun exposure, food, and vitamin supplements, must undergo a process called hydroxylation in two places in the body to become active. The first takes place in the liver, the other in the kidney. Therefore, the amount of active vitamin D is also affected in the problems that occur in these organs. According to the recommendations of the Institute of Medicine, the daily required amount of vitamin D for adults is 600 IU (international units), while this amount is 800 for those over 70 years old. Excessive intake of vitamin D can cause side effects. Therefore, no one should exceed 4000 IU daily.
How does vitamin D work?
In laboratory studies; Strong biological evidence has been obtained on the role of vitamin D in cancer prevention. Vitamin D; It can inhibit or activate certain genes that regulate cell growth and limitation of inflammation, reducing signaling molecules that allow cancer cells to spread. The role of vitamin D in these processes is an extremely active area of research.
Where did the idea that vitamin D protect against cancer first come from?
First, in the map of cancer death rates drawn by regions in the USA; The fact that some cancer types are significantly higher in northern states, where sun exposure is less, and less in southern states, has led to the idea that vitamin D is effective in protecting from some types of cancer. The sun is the main source of vitamin D. However, of course, this difference between different parts of the country may also be due to other differences among the people living in those regions. Therefore, studies have been initiated to investigate this issue.
Until now, the strongest association between vitamin D and cancer prevention has been seen in colon cancer. Many studies have found that those with high blood levels of vitamin D have a significantly lower risk of colon cancer compared to those with low blood levels. In a study of 3121 people over the age of 50 who underwent colonoscopy, those who took high daily amounts of vitamin D (>645 IU) had significantly less cancerous pre-cancerous lesions. In another comprehensive study with participants from 10 different European countries, a strong association was observed, with a lower risk of colon cancer in those with high pre-diagnosis blood vitamin D levels. In a study conducted on 1179 postmenopausal women, the rate of cancer development in 4 years was found to be significantly lower in those who took daily calcium (1400-1500 mg) and vitamin D (1100 IU) supplements. In another study conducted with 16000 participants, there was no relationship between vitamin D status and mortality rates in general, while mortality rates in colon cancer were seen less in those with high blood vitamin D levels. However, in a study conducted on approximately 36 thousand postmenopausal women; While the women were regularly given 400 IU of vitamin D and 1000 mg of calcium daily to one group, when the other group was divided into 2 groups and followed for 7 years, no significant difference was observed between the groups in terms of incidence of colon cancer.
In studies on the relationship of vitamin D with other types of cancer, clear evidence of its benefit could not be provided. In a study in which the data of 10 different studies were evaluated and analyzed together, no relationship was found between the level of vitamin D in the blood before diagnosis and cancers of the lymph, kidney, ovary, uterus, stomach, esophagus. The results of studies on its relationship with prostate and pancreatic cancer are inconsistent, and some studies have even claimed that high levels of vitamin D may increase the risk of these types of cancer. In a review study, high vitamin D levels in the blood were associated with an increased risk of pancreatic cancer. In another large-scale study that continued for more than 10 years, it was shown that vitamin D is effective in preventing aggressive breast cancer, and that insufficient vitamin D levels increase the risk of many types of cancer. However, another 2013 study of nearly 5,500 postmenopausal women found no association between vitamin D intake and breast cancer. It is thought that this inconsistency between the studies is due to the different methods used. For this reason, a comprehensive study was started to evaluate the relationship of vitamin D with the risk of colon and breast cancer with 21 different studies using the same methods. The results of the ongoing work will most likely be published next year, and we’ll be sure to share them with you when they’re published.
What Should I Do?
As a result; Although vitamin D is thought to be associated with cancer risk; It is not known clearly at which doses it is beneficial, at which doses it is harmful, and in which types of cancer it is effective. More well-designed, comprehensive studies are needed for this. The key for future studies will be to determine the ideal amount of vitamin D that reduces the risk of some types of cancer but does not increase the risk of others. However, until now, it is not possible to say anything clear about the effectiveness of vitamin D in the prevention of any type of cancer. Therefore, the use of vitamin D should not be encouraged in order to prevent cancer. At this point, make sure that the vitamin D needed for bone health is met with as much variety of foods as possible for now, and discuss with your doctor whether you need a vitamin D supplement. Depending on your health, your doctor can measure the level of vitamin D in your blood, but routine blood vitamin D measurement is not recommended to protect against cancer or other serious diseases.
