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Four Times the Recommended Vitamin D Dose Needed for Winter

vitamin D, RDA, dosage, sunshine, sun, sunlightMaintaining adequate levels of vitamin D during winter months requires a daily dose four times the current recommended dose, according to a new study.

The study has important implications for ongoing consultations on vitamin D recommendations. The current level of five micrograms (200 International Units) is seen by many as insufficient.

While your body does manufacture vitamin D in response to sunlight exposure, the levels of sun in some northern countries are so weak during the winter months that your body makes no vitamin D at all.

Vitamin D deficiency can cause or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases, cardiovascular diseases and diabetes.

Vitamin D Dose Recommendations
Age Dosage
Below 5 35 units per pound per day
Age 5 - 10 2500 units
Age 18 - 30 5000 units
Pregnant Women 5000 units
There is no way to know if the above recommendations are correct. The ONLY way to know is to test your blood. You might need 4-5 times the amount recommended above. Ideally your blood level of 25 OH D should be 60ng/ml.
Dr. Mercola's Comments:

I don’t know ANY single physical factor that could improve your health more than understanding and applying what we now know about vitamin D. Getting your blood levels tested and making sure your vitamin D levels are in the optimal range is especially important, no matter what your age is or where you live.

Current Recommendations for Vitamin D are Woefully Inadequate

There is overwhelming evidence showing that the current recommended daily allowances (RDA) for vitamin D are far too low to provide any of its well documented health benefits. Current RDAs are only:

  • 200 IU for adults up to age 50
  • 400 IU for adults aged 51 to 70
  • 600 IU for seniors over 70

At the end of last year, the American Academy of Pediatrics doubled its recommended dose of vitamin D for infants, children and adolescents, going from 200 to 400 units per day.  Unfortunately this is still a woefully inadequate recommendation as recent research reveals children may need TEN times that amount, or around 2,000 units per day!

According to the research, vitamin D at doses equivalent to 2,000 IUs is not only safe, but is actually necessary for achieving desirable vitamin D levels in children.

Compare that to the findings in this latest study, published in the Journal of Nutrition, which found that women in their twenties who live in Maine require daily intakes of 20 micrograms (800 IUs) to achieve what’s considered normal vitamin D status during winter months. 

Now, it’s very important to realize that what they’re referring to as “optimal” vitamin D status in this study is NOT actually optimal! It’s just the conventional “normal.”

800 IUs only brought the average vitamin D level in 80 percent of these women to 30 ng/L.

Folks, based on the latest clinical findings 50 ng/L is a deficiency state!

Clearly, they would need FAR more than 800 IUs to reach the optimal levels of 50-65 ng/L.

For those in the winter with no or very limited exposure to sunshine, 4,000-5,000 units per day would seem appropriate for most adults. If you are very heavy you may need to double that dose, and for children the dose can be half that.

However, your dosage may need to be even higher still.

According to vitamin D expert Dr. Heaney, your body requires about 4,000 IU’s daily just to maintain its current vitamin D level. So in order to raise your levels, you’d have to increase either your exposure to sunshine, or supplement with oral vitamin D3 (which I do not recommend without having your levels tested first).

Vitamin D Deficiency is Rampant

In the United States, the late winter average vitamin D is only about 15-18 ng/ml, which is considered a very serious deficiency state. In fact, it’s estimated that over 95 percent of U.S. senior citizens may be deficient, along with 85 percent of the American public.


  • Vitamin D deficiency is epidemic in adults of all ages who have increased skin pigmentation, such as those whose ancestors are from Africa, the Middle East, or India, who always wear sun protection, or who limit their outdoor activities.
  • African Americans and other dark-skinned people and those living in northern latitudes make significantly less vitamin D than other groups.
  • 60 percent of people with type 2 diabetes have vitamin D deficiency.

One U.S. study of women revealed that almost half of African American women of childbearing age might be vitamin D deficient.

The widespread deficiency in children and adolescents is particularly disturbing considering the many long-term health implications, both major and minor.  

For example, vitamin D has long been known to be essential for healthy bones, but a new study published in the Journal of Clinical Endocrinology & Metabolism just last month found that vitamin D is also positively related to muscle power and force in adolescent girls.  

Unfortunately, there are plenty of studies showing our youngsters are sorely deficient in this most important nutrient.  

Research from 2007 published in the American Journal of Clinical Nutrition, found about 55 per cent of seemingly healthy adolescents may be vitamin D deficient. A similar study from Britain in 2006 reported that over 70 per cent of seemingly healthy teenage girls were vitamin D deficient. 

Why You Need to Optimize Your Vitamin D Levels 

One recent meta-analysis of 18 randomized controlled trials has found that vitamin D significantly reduces mortality from all causes. That should be sufficient incentive for most to consider looking into optimizing your vitamin D levels. In fact, vitamin D deficiency is implicated in most of the diseases of modern civilization.

This is not surprising when you consider the fact that it is not “just a vitamin,” but rather the only known substrate for a potent, pleiotropic (meaning it produces multiple effects), repair and maintenance seco-steroid hormone that serves multiple gene-regulatory functions in your body.

Vitamin D's final metabolic product targets more than 2,000 human genes in a wide variety of tissues. It also produces over 200 anti microbial peptides, the most important of which is cathelicidin, a naturally occurring broad-spectrum antibiotic.

And, when you consider the fact that you only have 30,000 genes in your body, and vitamin D has been shown to influence more than 2,000 of them, the bigger picture of its true impact on your health can be easily understood. It may, in fact, have literally thousands of health benefits!

One group of researchers have calculated that simply increasing levels of vitamin D3 could prevent diseases that claim nearly 1 million lives throughout the world each year, as the widespread vitamin D deficiency seen today has been found to fuel an astonishingly diverse array of common chronic diseases.

For example, we now know that optimizing your vitamin D levels can help you prevent as many as 16 different types of cancer including pancreatic, lung, breast, ovarian, prostate, and colon cancers. Other studies have found that your vitamin D status has an impact on:

 Cancer  Hypertension  Heart disease
 Autism  Obesity  Rheumatoid arthritis
 Diabetes 1 and 2  Multiple Sclerosis  Crohn’s disease
 Cold & Flu  Inflammatory Bowel Disease  Tuberculosis
 Septicemia  Signs of aging  Dementia
 Eczema & Psoriasis  Insomnia  Hearing loss
 Muscle pain  Cavities  Periodontal disease
 Osteoporosis  Macular degeneration  Reduced C-section risk
 Pre eclampsia  Seizures  Infertility
 Asthma  Cystic fibrosis  Migraines
 Depression  Alzheimer’s disease  Schizophrenia


Your Take-Home Message

The first key here is to make sure you get plenty of appropriate exposure to sunshine (or a safe tanning bed) whenever possible, as that can supply you with as much as 20,000 IUs a day. An added boon is that there’s no risk of overdosing when going this route, so it virtually eliminates the need for blood testing.

However, if you use oral supplementation it becomes imperative that you monitor your vitamin D levels by blood testing, to make sure your levels are in the therapeutic range.

I advocate getting your vitamin D levels tested regularly, but as I reported recently, you now need to beware of where you’re getting your test done. For an in-depth explanation of what you MUST know before you get tested, please read my updated article Test Values and Treatment for Vitamin D Deficiency.