By Dr. Mercola

A robust and rapidly growing body of research clearly shows that vitamin D isabsolutely essential for good health and disease prevention, in part due to the fact that it influences about 10 percent of all your genes.

The US Preventive Services Task Force recently proposed new guidelines for vitamin D screening,1 which can be crucial for a number of different health conditions.

Unfortunately, the task force claims there’s “inadequate evidence” to make a determination about the value of routine vitamin D screening for people with asymptomatic vitamin D deficiency. As reported by CBS News:2

“Normally, our bodies make all of the vitamin D that we need by being out in the sun. However, the sunscreen that is used to protect us from skin cancer can also prevent us from getting enough vitamin D, especially during the winter.

…Vitamin D is a nutrient that helps your body absorb calcium for healthy bones. The greatest source is sun exposure… The panel agreed that vitamin D is important, but how much is needed remains unclear.

‘What we don’t know is exactly what levels really would classify someone as being deficient in vitamin D,’ Dr. Bibbins-Domingo explained.”

My Recommendation: Get Tested at Least Once a Year

In the end, the task force is leaving it up to individual doctors to make their own determinations as to whether a patient may benefit from vitamin D testing. My recommendation is to get your vitamin D level tested at least once per year, when your levels are likely to be at its lowest.

For people in the northern hemisphere, this would be around January or February. In the southern hemisphere, it would be around June or July. This is particularly important if you’re pregnant or planning a pregnancy, or if you have cancer.

From my perspective, it is simply reprehensible malpractice for a health care professional to fail to address your vitamin D level if you’re pregnant or undergoing cancer treatment—it’s just that important. For pregnant women, optimizing your vitamin D is more important for your child’s health and development than folate, which is routinely recommended for pregnant women.

Recent Studies Confirm Vitamin D’s Importance for Cancer Prevention

As for cancer, there are well over 800 references in the medical literature showing vitamin D’s effectiveness—both for the prevention and treatment of cancer.

Vitamin D has a number of potent anticancer effects, including the promotion of cancer cell death, known as apoptosis, and the inhibition of angiogenesis (the growth of blood vessels that feed a tumor).

Carole Baggerly, founder of the vitamin D research group GrassrootsHealth, believes that as much as 90 percent of ordinary breast cancer may in fact be related to vitamin D deficiency.

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According to a meta-analysis published in the March 2014 issue of Anticancer Research,3 patients diagnosed with breast cancer who had high vitamin D levels were twice as likely to survive compared to women with low levels.4,5,6

The high serum group had an average vitamin D level of 30 nanograms per milliliter (ng/ml). Women in the low serum group averaged 17 ng/ml, which is in fact the average vitamin D level found in American breast cancer patients.7

These findings indicate you need at least 30 ng/ml of serum 25-hydroxyvitamin D (25(OH)D) to prevent cancer from spreading. Other research suggests you’d be better off with levels as high as 80 ng/ml.

An even more recent study,8,9 published in the British Medical Journal on June 17, links vitamin D optimization to improved cancer prognosis among those with a family history of cancer—regardless of the type of cancer involved—and a reduced risk of death from any cause, courtesy of its multi-varied influence on your health.

Here, data from eight population-based studies were analyzed. All in all, the studies followed more than 26,000 Europeans and Americans, aged 50 to 79, over the course of a 16-year period.

The data showed a clear pattern: those with consistently lower vitamin D levels were more likely to die from various health problems, including cancer, compared to those with higher levels. According to the authors:

“Despite levels of 25(OH)D strongly varying with country, sex, and season, the association between 25(OH)D level and all-cause and cause-specific mortality was remarkably consistent.”

Optimizing Your Vitamin D Also Reduces Your Risk of Diabetes, New Study Suggests

In related news, an Indian study found that vitamin D and calcium supplementation in combination with exercise can aid prediabetic individuals by preventing the progression into full blown diabetes. Since exercise is one of the most effective ways to improve your insulin and leptin sensitivity, this certainly makes sense. As noted by Nephrology News:10

“Vitamin D deficiency has been linked to prediabetes, which is a blood glucose, or sugar, level that is too high but not high enough to be considered diabetes. It is unclear, however, if bringing low vitamin D blood levels to normal through supplementation will affect progression to diabetes.

In the new study, every unit increase in vitamin D level after supplementation of the vitamin decreased the risk of progression to diabetes by eight percent…

‘Without healthy lifestyle changes, nothing works to prevent diabetes in at-risk individuals,’ said the lead author, Deep Dutta, MD, DM… ‘However, our results are encouraging because the addition of vitamin D and calcium supplements is easy and low in cost.'”

Here, a vitamin D level below 30 ng/ml was considered insufficient. All participants in the study were prediabetic.

The treatment group received a once-weekly dose of 60,000 IUs of vitamin D3, along with 1,250 milligrams (mg) of calcium carbonate daily, for eight weeks. A second group received only the calcium supplement. Both groups were advised to get 30 minutes of daily exercise. More than two years’ worth of follow-up revealed that:

  • Just under 11 percent of those receiving both vitamin D3 and calcium became diabetic, while 26.5 percent of the calcium-only group developed diabetes
  • Blood sugar levels normalized in over twice as many of those in the vitamin D/calcium group, compared to the calcium-only group (41.8 percent versus 20.4 percent respectively)

Calcium/Vitamin D Supplementation Also Helpful for Gestational Diabetes

Similar results11 were found in another recent randomized placebo-controlled trial12 investigating the effect of calcium and vitamin D supplementation on the metabolic status of pregnant women with gestational diabetes (GDM).  The test group received 1,000 mg calcium daily. They also received 50,000 IUs of vitamin D3 at the outset of the study, and another 50,000 IUs three weeks later. The control group received placebos. After six weeks, the treatment group had “significant reductions” in fasting plasma glucose, insulin, and LDL cholesterol compared to the placebo group. The treatment group also showed improved insulin sensitivity, and had higher HDL cholesterol. According to the authors:

“Calcium plus vitamin D supplementation in GDM women had beneficial effects on metabolic profile… This is important because elevated circulating levels of inflammatory markers and impaired insulin metabolism in GDM can predict the progression to type 2 diabetes later in life and neonatal complications… In addition, increased inflammatory markers in GDM might predict the future development of both metabolic and cardiovascular disease.”

The Importance of Optimizing Your Vitamin D Level During Pregnancy Cannot Be Overstated

Optimizing your vitamin D levels prior to, or at the very least during, pregnancy is important for other reasons besides protecting against gestational diabetes. Previous research has shown that your levels need to be above 50 ng/ml to protect you and your baby from even more serious complications such as premature delivery and preeclampsia. So please, if you’re pregnant, make sure to get your 25 hydroxy D levels checked.

Previous research by Drs. Hollis and Wagner reveals even more reasons for addressing any vitamin D insufficiency during pregnancy. Their preliminary findings were discussed at a 2009 international vitamin D research conference in Brugge, Belgium,13 and included the following (the study was eventually published in 201114):

Mothers who took 4,000 IUs (10 times the RDA of 400 IU) of vitamin D daily during pregnancy decreased their risk of premature birth by half Women taking high doses of vitamin D had a 25 percent reduction in infections, particularly respiratory infections such as colds and flu, as well as fewer infections of the vagina and the gums
Women taking high doses of vitamin D reduced their chances by half of delivering their babies prematurely at both 32 and 37 weeks The “core morbidities of pregnancy” were reduced by 30 percent in the women who took the high-dose vitamin D. (Including diabetes, high blood pressure, and preeclampsia — a potentially deadly increase in blood pressure and fluid accompanied by low platelets)
Fewer babies were born “small for dates” Babies getting the highest amounts of vitamin D after birth had fewer colds and less eczema

According to Dr. Hollis: “I’m telling every pregnant mother I see to take 4,000 IUs and every nursing mother to take 6,400 IUs of vitamin D a day. I think it is medical malpractice for obstetricians not to know what the vitamin D level of their patients is. This study will put them on notice.”

How to Optimize Your Vitamin D Level

When it comes to vitamin D, you don’t want to be in the “average” or “normal” range, you want to be in the “optimal” range. Based on the evaluation of healthy populations that get plenty of natural sun exposure, the optimal range for general health appears to be somewhere between 50 and 70 ng/ml.

The Role of Vitamin D in Disease Prevention

A growing body of evidence shows that vitamin D plays a crucial role in disease prevention and maintaining optimal health. There are about 30,000 genes in your body, and vitamin D affects nearly 3,000 of them, as well as vitamin D receptors located throughout your body.

According to one large-scale study, optimal Vitamin D levels can slash your risk of cancer by as much as 60 percent. Keeping your levels optimized can help prevent at least 16 different types of cancer, including pancreatic, lung, ovarian, prostate, and skin cancers.

How Vitamin D Performance Testing Can Help Optimize Your Health

Is it any wonder then that no matter what disease or condition is investigated, vitamin D appears to play a crucial role? This is why I am so excited about the D*Action Project by GrassrootsHealth. Dr. Robert Heaney is the research director of GrassrootsHealth and is part of the design of the D*action Project as well as analysis of the research findings.

GrassrootsHealth shows how you can take action today on known science with a consensus of experts without waiting for institutional lethargy. It has shown how by combining the science of measurement (of vitamin D levels) with the personal choice of taking action and, the value of education about individual measures that one can truly be in charge of their own health.

In order to spread this health movement to more communities, the project needs your involvement. To participate, simply purchase the D*Action Measurement Kit and follow the registration instructions included. (Please note that 100 percent of the proceeds from the kits go to fund the research project. I do not charge a single dime as a distributor of the test kits.)

As a participant, you agree to test your vitamin D levels twice a year during a five-year study, and share your health status to demonstrate the public health impact of this nutrient. There is a $65 fee every six months for your sponsorship of this research project, which includes a test kit to be used at home, and electronic reports on your ongoing progress. You will get a follow up email every six months reminding you “it’s time for your next test and health survey.”

This article was republished with permission from

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Joseph Mercola
Health Expert
I am an osteopathic physician who believes that proper nutrition, not medicine, is the key to good health. I seek to treat the whole person, not just the symptoms. I offer you practical health solutions without the hype. Founded in 1997 which is now the most visited natural health site on the web with 1.5 million subscribers. My site is grounded on providing the latest health information and providing practical health solutions. The strategies I present in my newest book, “Fat for Fuel,” are just too valuable for your well-being. That’s why you should not pass up this chance to ensure your copy! Order here .