Higher vitamin D levels cut colorectal, breast cancer risk by 31 per cent
Researchers at University of California San Diego School of Medicine suggest higher levels of vitamin D are associated with decreasing risk of breast cancer. Their epidemiological study is published in the June 15 online issue of PLOS ONE, in collaboration with Creighton University, Medical University of South Carolina and GrassrootsHealth, an Encinitas-based nonprofit organization that promotes vitamin D research and its therapeutic benefits.
The scientists pooled data from two randomized clinical trials with 3,325 combined participants and a prospective study involving 1,713 participants to examine the association between risk of female breast cancer and a broad range of serum 25-hydroxyvitamin D (25(OH)D) concentrations, which was chosen as the marker because it is the main form of vitamin D in blood.
All women were age 55 or older. The average age was 63. Data were collected between 2002 and 2017. Participants were free of cancer at enrollment and were followed for a mean period of four years. Vitamin D levels in blood were measured during study visits.
Over the course of the combined studies, 77 new cases of breast cancer were diagnosed for an age-adjusted incidence rate of 512 cases per 100,000 person-years.Researchers identified the minimum healthy level of 25(OH)D in blood plasma to be 60 nanograms per milliliter, substantially higher than the 20 ng/ml recommended in 2010 by the Institute of Medicine, now the National Academy of Medicine, a health advisory group to the federal government. Some groups, such as GrassrootsHealth, have advocated higher minimums for health blood serum levels of vitamin D, as much as 50 ng/ml. The matter remains hotly debated.
“We found that participants with blood levels of 25(OH)D that were above 60 ng/ml had one-fifth the risk of breast cancer compared to those with less than 20 ng/ml,” said principal investigator and co-author Cedric F. Garland, DrPH, adjunct professor in the UC San Diego Department of Family Medicine and Public Health. Risk of cancer appeared to decline with greater levels of serum vitamin D.
Multivariate regression was used to quantify the association between 25(OH)D and breast cancer risk, with the results adjusted for age, body mass index, cigarette smoking and intake of calcium supplements, said first author Sharon McDonnell, an epidemiologist and biostatistician for GrassrootsHealth.
“Increasing vitamin D blood levels substantially above 20 ng/ml appears to be important for the prevention of breast cancer.”Also, a large new international study has found higher vitamin D levels significantly drive down colorectal cancer risk. The vitamin, found in fatty fish and sunshine, was found to strengthen resistance to stomach tumors by blocking a common gateway that cancer cells pass through – and it was most protective in women.
The study was published online in the Journal of the National Cancer Institute.The report, led by the Harvard TH Chan School of Public Health, adds weight to a long-suspected theory, which, until now, had not been proven.It also suggested the ideal amount of vitamin D we should be aiming for may be higher than current guidelines suggest.
This study is yet another reminder to prioritize loading up on vitamin D, since around three quarters of Americans and a fifth of Brits are deficient – but while the vitamin is hard to find in natural foods, experts warn to scrutinize supplements that may not have been tested rigorously.Garland, who has previously studied connections between serum vitamin D levels and several types of cancer, said the study builds upon previous epidemiological research linking vitamin D deficiency to a higher risk of breast cancer. Epidemiological studies analyze the distribution and determinants of health and disease, but it has been argued that they do not necessarily prove cause-and-effect.
“This study was limited to postmenopausal breast cancer. Further research is needed on whether high 25(OH)D levels might prevent premenopausal breast cancer,” Garland said. The population was also mainly white women so further research is needed on other ethnic groups.”Nonetheless, this paper reports the strongest association yet between serum vitamin D and reduction in risk of breast cancer,” Garland said.
Garland and others have advocated the health benefits of vitamin D for many years. In 1980, he and his late brother Frank C. Garland, also an epidemiologist, published an influential paper that posited vitamin D (produced by the body through exposure to sunshine) and calcium (which vitamin D helps the body absorb) together reduced the risk of colon cancer. The Garlands and colleagues subsequently found favorable associations of markers of vitamin D with breast, lung and bladder cancers, multiple myeloma and adult leukemia.
To reach 25(OH)D levels of 60 ng/ml, said Garland, would generally require dietary supplements of 4,000 to 6,000 international units (IU) per day, less with the addition of moderate daily sun exposure wearing very minimal clothing (approximately 10-15 minutes per day outdoors at noon). He said the success of oral supplementation should be determined using a blood test, preferably during winter months.
The current recommended average daily amount of vitamin D3 is 400 IU for children up to one year; 600 IU for ages one to 70 years (including pregnant or breastfeeding women) and 800 IU for persons over age 70, according to the National Academy of Medicine.A 2009 paper published in the Annals of Epidemiology by Garland and colleagues recommended a healthy target level of serum 25(OH)D of 40 to 60 ng/ml, based on an expert consensus panel. This statement was published in Annals of Epidemiology (2009). Oral doses of vitamin D are often not specified since different individuals require different intakes to achieve targeted serum range. Except under medical supervision and monitoring, intake of vitamin D3 must not exceed 10,000 IU per day. Blood serum levels exceeding 125 ng/ml have been linked to adverse side effects, such as nausea, constipation, weight loss, heart rhythm problems and kidney damage.
Meanwhile, previously, studies have been inconclusive about the cancer-fighting benefits of higher concentrations of circulating 25-hydroxyvitamin D, the accepted measure of vitamin D status.There have only been a handful of randomized clinical trials on vitamin D supplements and colorectal cancer – none of which found a connection.
The authors of the new study say that may be because the studies were too small, the supplements weren’t taken for long enough, or the subjects didn’t fully comply – because now, they claim, they have the clearest evidence yet that there is a concrete link.To find it, researchers conducted an analysis of more than 5,700 colorectal cancer cases and 7,100 controls from the United States, Europe, and Asia.
Compared to participants with circulating vitamin D concentrations considered sufficient for bone health, those with a vitamin D deficiency had a 31 percent higher risk of colorectal cancer during follow-up five years later.Strong bone health, which is affected by vitamin D levels, was also associated with a 22 percent lower risk.
These links persisted even after adjusting for known colorectal cancer risk factors.The protection was seen in all groups, but particularly in women.The lifetime risk of colorectal cancer is 4.2 percent (one in 24) in women and 4.5 percent (one in 22) in men.Colorectal cancer is the third most common cancer and third leading cause of cancer-related deaths in both men and women in the United States, with about 140,250 new cases and 50,630 deaths expected during 2018.