By Roberta H. Anding, MS, Baylor College of Medicine and Texas Children’s Hospital

Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily

As much of the hype surrounding vitamin E has largely been disproven, vitamin D has become the new rising hero in the nutrition world. In this case, though, it may be more than mere hype. Professor Anding explores the functions and current research surrounding this dynamic fat-soluble vitamin. 

A Dietary Essential?

In addition to vitamin D’s well-known role in the development of bone, current research is considering that vitamin D may be needed in the prevention and management of other chronic common conditions.

“This has become such a clinical issue for us at Texas Children’s and Sports Medicine that we now assess the vitamin D status of most patients coming in the door,” Professor Anding said. “We actually draw blood.” 

First, keep in mind that vitamin D is a fat-soluble vitamin that functions more like a hormone. It’s not truly a dietary essential because if you spend time in the sun, you can make it in your skin. 

Some of the confusion with numbers concerning vitamin D recommendations is because the current requirement is now under review.

“I will suggest to you the next time the government reviews and changes requirements, this is one that’s probably going to change, and by ‘change’ I mean increase,” Professor Anding said.

While vitamin D is best-known for its role in bone health, emerging science suggests that vitamin D has other functions as well. Vitamin D may aid in the prevention of cancer, diabetes, heart disease, and multiple sclerosis. It can even prevent schizophrenia because of how it impacts the brain.

Form and Function

As with other vitamin studies, though, form and function must be taken into consideration. Vitamin D belongs to a family of many compounds, with only two being the most biologically active. 

Ergocalciferol, found in a few plant-based foods such as mushrooms, is also known as vitamin D₂. Cholecalciferol is found in animal-based foods and is known as vitamin D₃.

Here’s where it gets a little tricky. The skin can make a version of vitamin D from cholesterol, which holds important biological functions. 

Vitamin D is sent to the liver and then on to the kidney for final activation. According to Professor Anding, this is a significant finding when it comes to toxicity because toxicity of vitamin D is in its fully activated form. 

According to Dr. Michael Holick, an international expert on vitamin D, having sun exposure— enough to induce mild redness—can be considered a dose of 20,000 International Units, so the sun becomes a powerful ally.

“Please don’t misinterpret this,” Professor Anding said. “I’m not trying to induce skin cancer in order to protect your vitamin D status.”

However, the fact that many of us spend so much time inside can lead to vitamin D deficiency. Additionally, because activation in the kidney and the liver is key to the bioavailability of vitamin D, you need a healthy kidney and liver. Thus, if you have pre-existing disease in either of those organs, you might not be able to activate vitamin D.

Roles of Vitamin D

The primary role of vitamin D is as a regulator. Consider it to be like the conductor of an orchestra.

Cell membranes and the nucleus of cells contain receptors for vitamin D. Vitamin D teaches each cell what it must do in terms of its physiological function. 

Additionally, vitamin D regulates blood calcium levels with the cooperation of other hormones, and it’s needed for normal beta cell function, which is responsible for the production of insulin. Some studies suggest it may prevent diabetes.

When it comes to multiple sclerosis, early studies suggest that the farther away you are north or south of the equator, the more likely you are to develop MS. If you are born and live for the first 10 years of your life above 35 degrees latitude, your risk of developing MS as an adult increases by 100%, according to a recent study in the Journal of American Medical Association.

Thus, living closer to the equator and having increased sun exposure is linked to a decreased risk of developing MS. By extension, then, we can infer that increasing your vitamin D intake can prevent MS.

Psoriasis is often considered an autoimmune disease, and some research suggests that vitamin D may protect your immune system. The current research on psoriasis and vitamin D suggests it might be an adjunct for the treatment, though it should not replace conventional medical therapy. Additionally, many studies support the role of vitamin D in cancer prevention because vitamin D acts as a cellular conductor, telling cells what to do and how to do their job.

This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.

Professor Roberta H. Anding is a registered dietitian and Director of Sports Nutrition and a clinical dietitian at Baylor College of Medicine and Texas Children’s Hospital. She also teaches and lectures in the Baylor College of Medicine’s Department of Pediatrics, Section of Adolescent Medicine and Sports Medicine, and in the Department of Kinesiology at Rice University.