Vitamin D: You Need It for Much More Than Your Bones

This crucial nutrient can be tough to get enough of if you aren't spending time in sunshine
January 2, 2020 Updated: January 2, 2020

Vitamin D plays a greater role in our health than many of us realize. Its importance in maintaining strong bones has been known for nearly a century, but what else does it do?

Vitamin D, or cholecalciferol, was 1 of 13 essential vitamins discovered by researchers in the early 20th century. After a long search, its discovery culminated in a cure for rickets, a painful childhood bone disease. Due to this medical victory over a bone disease, there’s been a strong association between vitamin D and bone health ever since.

While vitamin D is essential for health and firmly entrenched as one of the four fat-soluble vitamins (along with vitamins A, E, and K), it isn’t technically a vitamin. It’s generated by the human body with sunlight exposure and is found only in a few natural foods, such as fish and egg yolks. It behaves more like a sunlight-dependent hormone than a vitamin, but that doesn’t change its important position in our health. Interestingly, as we have transitioned from an active outdoor lifestyle to a more sedentary indoor lifestyle, we have become more and more dependent on fortified foods and supplementation to maintain adequate vitamin D levels.

This nutrient is so important to our continued health that varying skin tones throughout the world have been modified to ensure adequate intake. While there are many reasons for these variations in our skin color, a primary driver for lighter skin color, as humans migrated away from the equator into colder climes, was the need for adequate vitamin D levels as the sun’s rays became weaker.

Knowing the conservatism and practicality of human physiology, there must be more benefit from all this effort than just strong bones. Vitamin D is important to our health because it allows us to use calcium in an efficient manner. Calcium is critically important to how our bodies work, with hundreds of functions that require it. Calcium is one of the elemental building blocks of life on our planet with its uses including muscle contraction, blood clotting, blood pressure regulation, normal brain function, insulin utilization, and reproduction to name only a few.

Today, there is little debate in the medical community on the importance of vitamin D. Unfortunately, the actual blood level needed to achieve minimal, adequate, or optimal vitamin D levels isn’t so clear. These are definitions that are still evolving and there is still no consensus on what an optimal level of vitamin D is. Vitamin D testing has been one of the top Medicare labs ordered by doctors for many years now, so we know doctors are ordering and looking at these levels. Are their vitamin D targets effective for optimal or even adequate calcium delivery and function?

Most conventional doctors view a level of less than 20 ng/mL of 25 dihydroxyvitamin D (the active form of vitamin D in the body) as a deficiency and will supplement to raise it. A level of between 20 and 30ng/mL is considered borderline and will be supplemented in certain cases, such as osteoporotic women. A normal vitamin D level is considered anywhere within the broad range of 30–100 ng/mL.

Getting back to the origins of vitamin D discovery, these levels were established primarily with bone health in mind. Maintaining a level of 30 or higher, with adequate calcium intake, should give most of us strong and healthy bones. What about all the other functions of calcium in the body? Would a vitamin D level of 32 be enough to ensure proper immune function? A growing body of research points to levels of 60 or greater for optimal immune function.

From a functional medicine viewpoint, vitamin D is a critical component in optimal immune system response. There’s a large variety of immune cells that perform a broad range of functions, including turning on and off inflammation and they all require calcium to work properly. These connections with the inflammatory response are likely responsible for vitamin D’s diversity of effects, such as decreased rates of cancer and cardiovascular disease.

A functional medicine workup requires optimal vitamin D levels. This is essential when treating any disease involving inflammation and the immune system.  We target blood levels between 60 and 80 ng/mL. For a person who lives in a mild climate and spends the majority of their day outside, these levels may not be terribly difficult to obtain. However, in today’s world, the majority of people don’t meet this criteria and spend most of their day indoors. This can be further compounded in the winter months by shorter days and colder weather at higher latitudes. For these people (i.e. most of us), we need to go beyond the conservative recommendations of 600 IU per day from The Institute of Medicine (IOM). By dosing vitamin D at 5000 IU per day, we can usually achieve optimal levels in most individuals.

Some individuals, particularly those with dark skin, obesity, advanced age, chronic gut issues, and chronic inflammation may require higher doses. While vitamin D toxicity is an extremely rare but real occurrence, higher doses can pose a more real danger with hypercalcemia or increased blood calcium levels. If dosing beyond 5000 IU is necessary, then pairing vitamin D with vitamin K2 can decrease the chance of this adverse event. Vitamin K2, or menaquinone, is a bacterial by-product produced by our gut bacteria or from fermented foods such as natto and some cheeses. Vitamin K2 improves calcium absorption in the gut and therefore reduces the risk for hypercalcemia when using high doses of vitamin D.

While fears of vitamin D toxicity are overblown in my opinion, the piece about elevated levels of calcium in the blood is real and years of high dose supplementation could contribute to calcification of the arteries, joints, and other soft tissues. If you think you need more than 5000 IU daily, enlist the aid of a professional to guide your supplementation in the safest and efficient manner possible.

Don’t forget sun exposure. This is still the most efficient and healthiest way to maintain optimal vitamin D levels. It has been shown that as little as 13 minutes of sun exposure per day around noon in the United Kingdom during the summer months can maintain a normal vitamin D level. Thirty minutes of sun exposure in these conditions is equivalent to about 10,000–20,000 IU of vitamin D per day. Weather permitting, always start with sun exposure, keeping in mind the negatives side of sun exposure such as burns, skin aging, and increased skin cancer risk.

Many studies over the years have established increased energy, improved mood, and lower rates of cancer and cardiovascular disease when optimal vitamin D levels between 60 and 80 ng/mL were achieved. In my practice, this is the first step. Lower levels of vitamin D will place a ceiling on the effect of other treatments targeting inflammation and the immune system.

Achieving vitamin D levels of 60–80 ng/mL can be an easy and safe starting point in your journey for optimal health.

Armen Nikogosian, M.D., practices functional and integrative medicine at Southwest Functional Medicine in Henderson, Nev. He is board-certified in internal medicine and a member of the Institute for Functional Medicine and the Medical Academy of Pediatric Special Needs. His practice focuses on the treatment of complex medical conditions with a special emphasis on autism spectrum disorder in children, as well as chronic gut issues and autoimmune conditions in adults.