When Was the Last Time You Had Your Vitamin D Checked?

Understanding Vitamin D deficiency

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

Vitamin D is essential for optimal functioning. The great news is that we can produce it ourselves simply by going outside! Unfortunately, many Americans do not get enough. Professor Anding offers the remedy.

Woman looking at the sun
Photo By Nicoleta Ionescu / Shutterstock

Vitamin D Deficiency

Vitamin D deficiency can increase the fracture rate in older Americans and may also explain why some people don’t respond to traditional osteoporosis treatments. Estimates in the United States of vitamin D deficiency are emerging, and a study in the Journal of Pediatrics suggests that up to 50% of African American adolescents are vitamin-D deficient. 

Professor Anding believes that this is the major nutritional deficiency disease in the United States. The challenge is that for obese people, body fat sequesters or holds vitamin D in the body fat, which means it’s not available in the blood and thus cannot be utilized by your cells or central nervous system. 

Many experts believe we have an epidemic of vitamin D deficiency because the requirement is too low. This means that what you see as the 100% daily value on your supplement or your breakfast cereal label is probably not that level. Also, if you happen to be one of the two-thirds of Americans who are overweight, your vitamin D requirement is going to change based on the percent body fat that you have.

Some experts suggest that the vitamin D requirement should be for optimal blood levels, which may be as high as 2,000 International Units. That’s significantly more than the 200 International Units that is typically recommended by the government. 

Correcting Deficiencies

In order to correct blood levels, your physician may prescribe up to 50,000 International Units per month to correct the deficiency. You may think this is a toxic amount.

The reason your physician may prescribe this much is to correct the deficiency, and they may also suggest that you take vitamin D in your food in addition to another multivitamin. Should we be concerned about toxicity, though?

Sun exposure in the absence of skin cancer is not toxic as the skin can downregulate the amount of vitamin D precursor that’s actually sent to the liver and then sent onto the kidneys. Thus, if we’re making too much vitamin D from our skin, we’ve got the ability in our body to put the brakes on. 

The brakes can occur in the skin, the liver, and the kidney. The sun is not going to give you a toxicity of vitamin D. However, supplements can be toxic, and the Food and Nutrition Board has listed the upper tolerable limit at 2,000 International Units. 

You may be confused at this point, since you just read earlier that many experts are now listing 2,000 IU as the recommended amount. However, when considering the toxicity of vitamin D, most studies look at the fully activated form of vitamin D. 

Honestly, you can’t buy that over the counter. Vitamin D activation starts in the skin, goes to the liver, and then goes to the kidney. 

Avoiding Toxicities

The kidney—that final resting spot—makes that fully activated vitamin D. Most of the toxicity symptoms that you see are related to prescription, and not over-the-counter, vitamin D supplements. 

When it comes to 2,000 International Unit supplements that you can buy in the store, no toxicity symptoms have been documented at this level. If indeed you take the fully activated prescription vitamin D, classic symptoms include higher blood levels of calcium and calcification of soft tissues. Again, though, this is only going to occur in the fully activated version.

The key is to get your blood level of vitamin D checked at your next doctor’s visit. This is going to be the best guarantee that you are getting an adequate amount, and your blood level should be greater than 30 nanograms per milliliter. By knowing our blood level, we can forestall or prevent some chronic illnesses.

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.

About Kate Findley 450 Articles
Kate is a writer, novelist, and blogger living in Los Angeles. She has been writing for The Great Courses since 2017. It incorporates her two favorite things: writing and learning.