Having high blood levels of vitamin D lowers the risk of several cancer forms, according to a new study of Japanese adults. The study is the first to take a closer look at how vitamin D affects an Asian population. Over the past decades, numerous studies have pointed to vitamin D’s role in cancer prevention. Meanwhile, other studies have demonstrated that there is widespread vitamin D deficiency. There is even evidence suggesting that our need for the nutrient exceeds the official recommendations, at least if we want to protect ourselves against cancer.
Around 30 percent of the Danish population gets cancer. Even with nationwide cancer fundraising projects coupled with cancer awareness TV shows, we still have not been able to break the curve. On the contrary. According to the Nordic cancer database, Nordcan, the cancer rate is believed to increase by more than 50 percent within the near future and many of those people who otherwise follow the official diet and exercise guidelines are also at risk.
Although many things can cause cancer, it looks as if vitamin D plays a both significant and somewhat overlooked role.
The sun is the primary source of vitamin D, but many people avoid the sun, and during the winter period, the sun sits too low in the sky to enable vitamin D synthesis in the skin of people living at northern latitudes.
As far back as in the 1940s, researchers noticed a link between UVB exposure from sunrays and cancer mortality. People who lived in the northern hemisphere had an increased risk of several different cancer forms compared with people who lived closer to Equator.
New study of vitamin D’s cancer preventive effect on Asians
According to the Japanese scientists, their new study supports earlier studies in showing that vitamin D has the potential to protect against several cancer forms. Vitamin D is primarily known for its role in calcium uptake, which is important for bones, teeth, and muscles. However, research conducted over the past decades has unveiled that vitamin D is also important for preventing an array of chronic diseases, including cancer. The majority of these studies is carried out on white, Caucasian populations of Europe and the United States, leaving only limited focus on Asian population groups.
Because the synthesis and the activation of vitamin D plus blood levels of the nutrient can vary from one ethnic group to another, the Japanese scientists decided that it was important to investigate whether the vitamin had similar anti-cancer properties in a non-Caucasian population.
An international team of scientists based in Japan therefore looked at whether vitamin D deficiency is linked to cancer in general, and if there is a link to specific cancer forms.
Vitamin D offers 20-50 percent cancer protection
The scientists analyzed data from a large Japanese health study (JPHC), which included 33,736 men and women aged 40-69 years. At baseline, the participants were asked to provide detailed information about their medical history, diet, and lifestyle, and blood samples were taken in order to determine levels of vitamin D in their blood.
The vitamin D levels were higher during summer and autumn and lower during winter and spring, which corresponds with the sun’s location in the sky at different times of the year. The researchers therefore adjusted for these season-related differences, and then they categorized the participants in four groups, ranging from lowest to highest in terms of vitamin D levels in the blood.
The study participants were followed for approximately 16 years. During this period, 3,301 new cases of cancer were diagnosed. After adjusting for several known cancer risk factors such as smoking, alcohol, age, BMI, physical activity level, and diet, the researchers observed that a high vitamin D content in the blood lowered the risk of cancer by around 20 percent in men and women. With liver cancer specifically, the risk reduction was 30-50 percent, with the largest reduction in men.
The scientists did not find a relation between vitamin D levels and lung cancer or prostate cancer. They said that the study has certain limitations in that the number of participants was too small to study the relation between blood levels of vitamin D and more rare cancer forms. Nonetheless, this Japanese study supports several other trials that have shown how vitamin D protects against cancer. The researchers call for future studies in order to pinpoint the optimal levels blood levels of vitamin D for cancer prevention.
Did you know that vitamin D influences most cells in the body and more than 200 genes?
Previous Danish study: Lack of vitamin D causes cancer
Having low levels of vitamin D in the blood increases your risk of cancer and premature death by 30-40 percent, according to a large Danish study that is published in the esteemed British Medical Journal. Lead investigator, Børge Nordestgaard, professor at the University of Copenhagen and chief physician at Herlev Hospital, says that a person with only 30 nmol/l of vitamin D in the blood (20 nmol/l below the official recommendation) has a 40 percent increased risk of dying of cancer.
Did you know that women who are out in the sun a lot are half as likely to develop breast cancer as are those who get less sun?
A comprehensive European study has shown a relation between low vitamin D levels in the blood (less than 50 nmol/l) and an increased risk of colon cancer. Also, people with higher blood levels of the nutrient had a 40 percent lower risk of colon cancer.
Alarming vitamin D deficiency
DTU Food (The National Food Institute) of Denmark reckons that nine out of 10 Danes get too little vitamin D from the diet. Also, an Australian study has shown that 58 percent of the Australians lack vitamin D, so living in a warm climate is no guarantee of having adequate vitamin D in the blood. You need to expose your skin to the sun.
Vitamin D deficiencies have become increasingly common over the past decades because people are spending more time indoors, avoiding the sun, staying off dietary fats, using sunscreen, and taking cholesterol-lowering drugs for prolonged periods. In addition, older people, diabetics, and people with dark skin may have difficulty with synthesizing vitamin D in their skin.
New threshold values urge wintertime supplementation
The recommended threshold value for vitamin D (measured as 25-hydroxy vitamin D) in the blood is 50 nmol/l. Still, leading experts claim the values should be higher, suggesting 75-100 nmol/l for optimal disease prevention. According to Dr. Jens-Erik Beck Jensen, chief physician at Hvidovre Hospital in Denmark, the diet alone is unable to provide that much vitamin D.
Many scientists recommend going beyond the official vitamin D recommendations
Many experts claim that the actual need for vitamin D is way beyond the official recommendation (reference intake level) and suggest (for adults) anywhere from 30 to 100 micrograms daily. It is easy to synthesize that amount on a hot summer’s day, provided your skin is light. The darker your skin is, the longer it takes for it to produce the vitamin. As mentioned earlier, even a healthy diet only contributes with limited amounts of vitamin D, so during the entire winter period and in other situations where it is not possible to get vitamin D from sunlight, supplements are necessary. We also need magnesium to help the body convert vitamin D from sunlight and supplements (in the form of cholecalciferol) to 25-hydroxy vitamin D and one other active form. Because vitamin D is lipid-soluble, we are best able to utilize it by taking it as a supplement in capsules with oil.
Vitamin D and its anti-cancer properties
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Science News. Higher Vitamin D levels may be linked to lower risk of cancer. ScienceDaily March 2018
Shoaib Afzal et al. Genetically low vitamin D concentration and increased mortality: mendelian randomization analysis in three large cohorts. BMJ 2015
Densie Webb, PhD, RD: Vitamin D and Cancer – Evidence Suggest This Vital
Nutrient may Cut Risk. Today´s Dietician. 2012
Grant WB et al. The association of solar ultraviolet (UVB) with reducing risk of cancer: multifactorial ecologic analysis of geographic variation in age-adjusted cancer mortality rates. Anticancer Res 2006
WU K et al. A nested case control study of plasma 25-hydroxyvitamin D concentrations and risk of colorectal cancer. J Natl Cancer Inst 2007
Andreas R Raven: Langvarigt skifteholdsarbejde giver dobbelt kræftrisiko. Videnskab.dk 2013
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