In the heart of winter with very little sunshine or even time outside for that matter the body’s need for Vitamin D becomes even more apparent.

Think Seasonal Affective Disorder, a condition of inadequate sunlight which can often be improved by increasing vitamin D levels.

If you live north of the line connecting San Francisco to Philadelphia and Athens to Beijing, odds are that you don’t get enough vitamin D.

The same holds true if you don’t get outside for at least a 15-minute daily walk in the sun. Those with darker skin, as well as older individuals, tend to have much lower levels of vitamin D, as do people who are overweight or obese.

Benefits of Vitamin D

Vitamin D is actually not a vitamin at all; it’s a steroid hormone produced by the skin.

When the melanin in your skin is exposed to ultraviolet light it’s converted into Vitamin D with the help of cholesterol. The more melanin you have, the darker your skin tone, and the harder it is to convert into vitamin D.

As a steroid hormone, Vitamin D regulates over 1000 different physiological processes.

It’s involved in many aspects of your health. Let’s take a look at just 6 of these functions.

1. Improved Immunity

Immune cells have receptors for Vitamin D and its been shown that Vitamin D may help cells target and attack bacteria and viruses as well as prevent prolonged or excessive inflammatory responses.

This becomes important in reducing your risk for colds, flu, and other infections as well as decreasing the risk for autoimmune diseases, such as psoriasis, Type 1 Diabetes, or Multiple Sclerosis.

Multiple sclerosis (MS) rates are much higher far north (or far south) of the equator than in sunnier climates, and researchers suspect that chronic vitamin D deficiencies may be one reason why. One prospective study to look at this question found that among white men and women, those with the highest vitamin D blood levels had a 62 percent lower risk of developing MS than those with the lowest vitamin D levels.

Evidence that vitamin D may play a role in preventing type 1 diabetes comes from a 30-year study that followed more than 10,000 Finnish children from birth: Children who regularly received vitamin D supplements during infancy had a nearly 90 percent lower risk of developing type 1 diabetes than those who did not receive supplements.

Other European case-control studies, when analyzed together, also suggest that vitamin D may help protect against type 1 diabetes.

2. Cancer Prevention

Vitamin D deficiency has been correlated with increased risks for cancer development, particularly breast, colon, and prostate. (study, study)

The evidence is strongest for colorectal cancer, with most (but not all) observational studies finding that the lower the vitamin D levels, the higher the risk of these diseases. (Harvard School of Public Health: 28–38)

3. Bone Health

Vitamin D is important in the absorption of calcium into the bones. It plays a role in the balance of vitamin K and phosphorous, both of which are also important to the health of our bones.

A deficiency can result in the softening of the bones, increasing the risk for osteoporosis and fractures. Several studies link low vitamin D levels with an increased risk of fractures in older adults, and they suggest that vitamin D supplementation may prevent such fractures—as long as it is taken in a high enough dose.

Researchers found that high intakes of vitamin D supplements—of about 800 IU per day—reduced hip and non-spine fractures by 20 percent, while lower intakes (400 IU or less) failed to offer any fracture prevention benefit.

Vitamin D may also help increase muscle strength, which in turn helps to prevent falls, a common problem that leads to substantial disability and death in older people. Once again, the dose matters: A combined analysis of multiple studies found that taking 700 to 1,000 IU of vitamin D per day lowered the risk of falls by 19 percent, but taking 200 to 600 IU per day did not offer any such protection.

4. Heart Health

Vitamin D is thought to be involved in regulating blood pressure and cholesterol levels, in addition to inflammation. The heart is basically a large muscle, and like skeletal muscle, it has receptors for vitamin D.

The Health Professional Follow-Up Study checked the vitamin D blood levels in nearly 50,000 men who were healthy, and then followed them for 10 years. They found that men who were deficient in vitamin D were twice as likely to have a heart attack as men who had adequate levels of vitamin D.

Other studies have found that low vitamin D levels were associated with higher risk of heart failure, sudden cardiac death, stroke, overall cardiovascular disease, and cardiovascular death.

5. Brain Health & Mood

Since vitamin D acts as a hormone in our body and affects brain function, deficiency has been linked to an increased risk for mood disorders like depression.

Several studies also suggest that adequate levels of vitamin D may help with basic brain function, like concentration, learning, and memory.

There has long been concern regarding vitamin D deficiency and it’s potential role in the development of autism. Results from a recent randomized, double-blind, control trial showed promising effects of high-dose supplementation of vitamin D3 (up to 5000 IU/day) and the significant decrease of autistic symptoms.

6. Pain Management

A number of epidemiological studies have shown connections between low levels of vitamin D and non-specific musculoskeletal pain, headache, and fatigue. Correlations to the prevalence of chronic pain have also been found for geographical latitude and season of the year. Supplementing with vitamin D may then be an important adjunct in the treatment of chronic pain.

Vitamin D Deficiency

Worldwide, an estimated 1 billion people have inadequate levels of vitamin D in their blood, and deficiencies can be found in all ethnicities and age groups.

Researchers, such as Dr. Michael Holick, author of The Vitamin D Solution, estimates that up to 50% of the American population may be vitamin D deficient.

The National Health and Nutrition Examination Survey found that 50% of children aged 1 to 5 are deficient and 70% of children between the ages of 6 to 11 are deficient.

While years ago people spent more time outdoors, walking to do errands and even working outside, today we see a different situation. Most children are spending most daylight hours inside; watching television, playing video games, surfing the internet etc. And similarly, most adults work indoors, exercise inside gyms, and spend their free time inside their homes where they are sheltered from the sun.

Optimal Levels

There is some disagreement in the medical community regarding what an optimal range of vitamin D should be. Based on the above benefits I think this is an area where we don’t just want to have a normal amount of vitamin D, we want an optimal amount.

Some experts recommend aligning our ranges to healthy populations of humans living in tropical or sub-tropical environments with higher levels of sun exposure. Theoretically this would be most aligned with what we physiologically evolved from.

Here are the ranges I like to use.

Source: Dr. Mercola Website

In determining your blood levels, there are two different vitamin D tests. The correct one to get is 25(OH)D, or 25-hydroxyvitamin D.

Before adding in a supplement I recommend getting a Vitamin D test so you know how much you should be supplementing with to get up to an optimal level. I also suggest re-checking your levels in 3-6 months to make sure the amount you’re supplementing with is having the desired effect.

How Do We Get Vitamin D

Sunshine

There’s no question about it. Sunshine will always be your best source for vitamin D. However, if you put a sunscreen on with a sun protection factor of 30, it reduces your ability to make vitamin D in your skin by about 95 to 98 percent.

Instead, I recommend 10-20 minutes of uncovered exposure to the sun (arms, legs, abdomen, or back) most days. This amount of exposure can produce between 1000-10,000 IU of vitamin D.

This of course varies quite a bit depending on where you live and how light or dark your skin is. The darker your skin and the farther north you live the longer you have to be exposed. For example, if you lived in Boston you would need about an hour of sun exposure in the summer to produce ~1000 IU of D.

Foods

There are some food sources of Vitamin D, however as you can see from the list, not many.

• Fatty Fish – Halibut & Mackerel have the most vitamin D (~800-900 IU/filet), salmon (730 IU/filet), Trout & Swordfish (~500 IU/filet), Tuna & Sardines (~250-200 IU/can)
• Mushrooms – mushrooms contain plant sterols that convert UV light to Vitamin D, much like our skin, therefore mushrooms grown outdoors will naturally have higher levels of vitamin D. Maitake mushrooms seem to have the highest amount (~780 IU/cup)
• Egg Yolk – ~40 IU/egg
• Fortified Foods – however much of the added vitamin D is D2 which is not as absorbable as D3.

Supplements

For many of us, supplementation is still going to be a very good option, especially in the winter months. Make sure that you’re supplementing with Vitamin D3 rather than Vitamin D2.

D3 is believed to convert into the active form about 500 times faster than D2 and has been estimated to be up to 4 times more effective. So if you’re going to supplement with Vitamin D you want to make sure it’s D3.

Depending on what your Vitamin D levels are, you may want to supplement anywhere from 1000-5000 IU/day. If you are very deficient, then your physician will likely recommend supplementing even higher until your levels recover.

Vitamin D is a fat-soluble vitamin. This means it needs fat in order to be absorbed properly in the body. So choose a supplement that is oil-based and I would also suggest taking it with a meal. I find that Nordic Naturals and Carlson Labs both make very good Vitamin D3 products.

Take Home Message

Based on the hundreds of research studies out there pertaining to Vitamin D it is obviously a very important nutrient for our health. And this is true for both adults and children.

I suggest everyone get your levels checked so you know how you stack-up and add a supplement if necessary.

Get out into the sunshine as much as possible and choose vitamin D rich foods on a regular basis.

If you need any help in deciding how much Vitamin D to supplement, please feel free to reach out to me. I know how challenging it is to sift through all the different information and recommendations out there pertaining to supplementation. We can work together to determine what supplements, including vitamin D, are important for you.

I also highly recommend the following resources to educate yourself further on the importance of Vitamin D:

• Dr. Michael Holick — The Leading Authority on Vitamin D
• The Vitamin D Council