90% of my patients, especially my pediatric patients, who come in to see me for the first time have a vitamin D deficiency. Many of these patients are already taking a vitamin D supplement, most commonly 1,000 IU daily. Surprisingly, in more than half of these patients, their primary care physicians have told them that their vitamin D levels are normal, and many have never had anyone offer to draw and measure it. Vitamin D testing and repletion is a powerful tool to improve a range of conditions that can result from a deficiency in vitamin D.

Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Vitamin D obtained from sun exposure, food, and supplements is really unavailable to the body and must undergo two hydroxylations, or transformations, in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D, also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D, also known as calcitriol.

What Does Vitamin D Do in the Body?

Keeps you healthy: Getting a sufficient amount of vitamin D is important to maintain bone density and dental health and to improve resistance to certain diseases. It is also known to keep insulin, calcium and phosphorus levels in balance. If our body becomes deficient in this important vitamin, the risk of bone abnormalities such as osteomalacia (soft bones) or osteoporosis (fragile bones), cardiovascular disease, autoimmune diseases and chronic inflammation are increased.

Immune system: Vitamin D plays a role in promoting cell growth, supporting your immune function, and in reducing inflammation. As such, increasing vitamin D can help you fight off that nasty flu bug or head cold that may be going around. Additionally, new studies are revealing the role vitamin D plays in warding off several chronic diseases, including heart disease, multiple sclerosis, and diabetes.

Your muscles: New studies indicate a link between vitamin D and muscle function, including recovery from exercise and daily activities. It also explains why lower levels of vitamin D can lead to physical fatigue.

Happy, happy: Do you seem to have a certain bounce in your step when the sun is out? According to a study from the University of Texas, those who have lower levels of vitamin D in their blood are at greater risk of suffering from clinical depression. The key to proper sun exposure is moderation, sunburn prevention and knowing the sun sensitivity of your skin type.

Peaceful gut: Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) are often associated with low vitamin D levels. This is because vitamin D regulates the integrity of the intestinal mucosa, and, as vitamin D drops, the intestinal cells get weak and lose connection with each other. This triggers an inflammatory response, and tissues get irritable and overly responsive to triggers.

Cardiovascular health: Vitamin D reduces a hormone called renin that is believed to play a role in some causes of hypertension.

There is so much more that Vitamin D does for us and the research just goes on and on.

What is the Appropriate Amount of Vitamin D to Take?

This question is where it gets confusing. For so long we have had a recommended daily allowance that recently increased from 400 to 800 IU’s daily. However, 400 IU’s of vitamin D causes a different serum level in each person. It depends on the quality of supplement, a person’s individual issues with absorption, the amount of fat they have on their body among other things. Instead of focusing on an amount to take daily we need to be focusing on the serum level of vitamin D in a person’s blood.

The “normal” reference range for vitamin D is between 30-90 ng/dL. I don’t think I have ever met anyone who feels good at 30, yet this is what most primary care physicians are calling “normal”. When these patients get to me, they are exhausted, depressed, have low testosterone and poor thyroid function. Many people with vitamin D this low experience joint pain, muscle pain, GI problems and acne. Getting their vitamin D level in the blood up from 30 to 90 ng/dL makes an enormous difference, and for many patients, it is this simple thing that can improve so many different symptoms at one time.

But many doctors don’t offer to measure vitamin D because insurance doesn’t pay for it. This is an entirely separate problem. But, despite this ridiculousness, people should be given a choice to pay for it. And when they understand how important it is to their health, they usually do.

Get your vitamin D tested. Once you have the number up, retest every fall and summer. This is the easiest and one of the best things you can do for your health!