Does Vitamin D Prevent Again and Reduces Risk of Cancer
, by NCI Staff
Findings from a large clinical trial prove that taking vitamin D supplements does not lower cancer adventure.
Credit: iStock
In the largest-ever randomized clinical trial testing vitamin D for cancer prevention, the supplement did not reduce the take chances of developing cancer.
A large body of epidemiology research had suggested that people with higher claret levels of vitamin D have a lower gamble of cancer, said Barry Kramer, M.D., manager of NCI'south Division of Cancer Prevention.
However, such studies can merely highlight associations, not evidence cause and event, he added. "This is why it'southward important to question intuitions and observational epidemiology studies, and fund large-scale trials," Dr. Kramer connected; they tin can conclusively show whether a handling—in this case, a dietary supplement—truly can help to prevent cancer.
Results from the trial, called the Vitamin D and Omega-3 Trial (VITAL), were published November 10 in the New England Journal of Medicine (NEJM).
Isolating the Effects of Vitamin D
The body produces vitamin D when the skin is exposed to sunlight. The vitamin is also found naturally in some foods, such as fat fish and mushrooms, and is often added to others, including milk and some cereals.
For people with known vitamin D deficiencies, supplementation is recommended to maintain bone health and prevent fractures. "The chief goal of VITAL was to see if there's benefit to getting above the recommended dietary allowance, more what is considered necessary for os health," explained JoAnn Manson, M.D., of Brigham and Women's Hospital and Harvard Medical School, who led the study.
Observational studies take suggested that people who take vitamin D supplements may accept a lower hazard of many diseases. Simply "people who accept vitamins may be very different in important means from people who don't have vitamins," explained Dr. Kramer. They oft have a higher income and are less likely to fume, less probable to be overweight, and more likely to accept health insurance, he added—all of which are strongly linked with a lower risk of a variety of chronic health conditions, including heart disease and many cancers.
Large randomized clinical trials with thousands of participants tin can avoid these biases past randomly assigning study participants to receive or not receive the treatment.
VITAL was designed so that it could study the effects of both vitamin D and omega-3 supplements. The trial's primary endpoints—the central outcomes it measured—were the supplements' impact on the risk of developing cancer and middle disease. Information technology too had several secondary endpoints, including the hazard of dying from cancer. VITAL was funded primarily by NCI and the National Heart, Lung, and Blood Institute.
Virtually 26,000 participants with no history of invasive cancer or cardiovascular illness enrolled in the trial. Men had to be age 50 or older, and women age 55 or older, to enroll in the study. About half of the participants were women, and the participants were racially diverse, with most 20% being African American.
"The number of participants and the substantial proportion of black participants brand this cohort a nationally representative sample," wrote John Keaney, Thou.D., and Clifford Rosen, M.D., of the Academy of Massachusetts Medical Schoolhouse and the Maine Medical Centre Inquiry Constitute, in an accompanying editorial.
Participants were randomly assigned to one of 4 groups: daily vitamin D plus a placebo, omega-3 supplements plus a placebo, both vitamin D and omega-iii supplements, or 2 placebos. The researchers followed the participants for a median of 5.iii years.
Near 17,000 participants provided claret samples at the first of the trial, one,600 provided a second sample a year into the study, another 5,000 provided follow-up claret samples at later time points. The researchers used these samples to measure claret levels of vitamin D and omega-3s in the different groups.
Higher Vitamin D Levels Did Non Pb to Greater Benefit
Participants taking vitamin D saw their blood levels of the vitamin rise by xl% on average during the trial. Even so, despite this rising, the incidence of invasive cancer was about the same betwixt the groups: 793 participants in the vitamin D group (six.1%) received a cancer diagnosis during the trial, compared with 824 in the placebo grouping (6.iii%). The incidence of cardiovascular events (such every bit heart attacks) was too similar between the vitamin D and placebo groups.
Over the follow-up menstruum, in that location were 341 deaths from cancer: 154 among participants who took vitamin D (1.ane%) and 187 among those who took the placebo (1.4%). Although this difference was not statistically meaning, the difference in cancer deaths betwixt the groups started to widen over time, the researchers reported.
The researchers programme to follow the participants for another two to 5 years, to run into if a statistically pregnant difference in cancer deaths emerges. Laboratory studies have suggested that high blood levels of vitamin D may subtract the aggressiveness of cancer cells and the likelihood of metastasis, explained Dr. Manson. If then, longer follow-up will be needed to assess its effects on the take chances of death from cancer, she added. Other studies have suggested that regular use of vitamin D supplements may reduce the take a chance of dying from cancer, she said.
Supplementation with omega-3 fat acids likewise did not significantly reduce the risk of cancer incidence or cancer death. Those results were presented in a separate paper, also published in NEJM.
No increased adventure of side effects—including high blood calcium levels for vitamin D, haemorrhage with omega-3s, or gastrointestinal upset for either supplement—were plant among people taking the supplements at these doses, compared to rates in the placebo groups.
Futurity Paths for Vitamin D Inquiry
The VITAL trial "was well designed," said Dr. Kramer. "And when information technology's important to get the answer right— that is, when you're potentially making recommendations to hundreds of thousands, or even millions, y'all desire to make certain that your recommendations are based on very strong evidence," he added.
Other research into vitamin D and cancer prevention is ongoing, such as studying whether some types of cancer may be more than sensitive than others to the effects of supplementation.
For instance, an NCI-sponsored clinical trial is currently looking at whether supplementation with vitamin D, calcium, or both tin prevent the development of new colorectal adenomas in people who have already had one or more such precancerous growths removed. VITAL will too examine furnishings of the supplements on the take chances of new colorectal adenomas.
Dr. Manson and her colleagues programme to follow the participants for at least 2 more years and hope to secure grant funding to follow them for a longer menstruation, she said. They would besides similar to report the potential influence of genetics on the furnishings of vitamin D supplementation.
"This is something we really desire to look at—whether at that place are gene variants related to vitamin D metabolism, the vitamin D receptor, binding proteins, or even completely divide mechanisms, that could have influenced the effects of supplementation and could help identify those most likely to benefit," Dr. Manson said.
The VITAL results don't give reason for people taking vitamin D as recommended by their doctors to terminate, she continued.
"If you lot take a clinical indication for taking vitamin D, such as a os health trouble or malabsorption condition, or use of other medications that interfere with the bioavailability of vitamin D—then of course you should keep taking it," she concluded.
Source: https://www.cancer.gov/news-events/cancer-currents-blog/2018/vitamin-d-supplement-cancer-prevention
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