Don't Check Vitamin D

A new Endocrine Society Clinical Practice Guideline was published 6/2/24 and is getting lots of press. Key recommendations included:

• Do not routinely check vitamin D levels in healthy adults, including those with dark complexions or obesity.
• If taking vitamin D supplements, use daily, lower-dose vitamin D instead of non-daily, higher-dose vitamin D.
• In the general adult population aged 18-74 do not give empiric vitamin D supplementation, and do not test for vitamin D levels.
• In the general population aged 75 and older, do not routinely test vitamin D levels, but do give empiric vitamin D supplementation because of the potential to lower the risk of mortality. Daily lower dose vit D is preferred over higher dose non-daily vitamin D.
• During pregnancy, give empiric vitamin D supplementation, given its potential to lower risk of preeclampsia, intra-uterine mortality, preterm birth, small-for-gestational-age birth, and neonatal mortality. Do not routinely check vitamin D levels during pregnancy.
• For adults with high-risk prediabetes, give empiric vitamin D supplementation to reduce the risk of progression to diabetes.
• Give empiric vitamin D to children from 1-18 years of age to prevent nutritional rickets and potentially lower the risk of respiratory tract infections. Empiric supplementation can be achieved by fortified foods and if needed supplements. The dose in the clinical trials for this age group varied but had a weighted average of 1200 IU daily.

While there have been widespread calls for universal vitamin D supplements and testing, these Endocrine Society Guidelines provide a much-needed comprehensive review of the evidence. The evidence does not support the need for vitamin D supplements in most healthy adults below 75. Their advice about testing (mostly don't test) and supplements (mostly not needed in healthy adults under 75) is firmly rooted in a careful review of the current evidence.

Many (see here) are angry about the recommendations, believing vitamin D supplements help with immunity, preventing or moderating covid-19, bone disorders, etc. Yet solid evidence does not support it.

Regarding what dose of vitamin D to use if needed, as a Medscape commentary stated:

The document acknowledges that the optimal dose for these populations isn't known, but it provides the dose ranges that were used in the trials cited as evidence for the recommendations. ...the document advises against more vitamin D than the recommended daily intake for most healthier adults younger than 75 years

The guideline does not address or apply to those with an indication for vitamin D testing, such as abnormal calcium levels, osteoporosis, chronic kidney or liver disease, or many GI disorders, such as inflammatory bowel disease.

Sources of Vitamin D

Where does vitamin D come from? UV-B rays on the skin are our natural method for getting vitamin D. How much sun exposure do we need? A UCLA doc answered this:

A study done in Valencia, Spain, measured the amount of sunlight necessary to produce a sufficient amount of vitamin D in those with lighter skin. (Valencia is about the same latitude as Kansas City, Missouri.) The researchers took into account the amount of clothing and the season of the year. In spring and summer, 25 percent of the body (the hands, face, neck and arms) is exposed to the sun, and in these seasons, about 8 to 10 minutes of sun exposure at noon produces the recommended amount of vitamin D. In the winter, only 10 percent of the body is exposed, and nearly 2 hours of sun exposure at noon is needed to produce a sufficient amount of vitamin D.

Less time is needed in Miami, more in Boston. However, since sun exposure increases skin cancer, going out in the sun to get vitamin D is not recommended.

What about food? The National Institutes of Health says that "few foods naturally contain vitamin D. The flesh of fatty fish (such as trout, salmon, tuna, and mackerel) and fish liver oils are among the best sources.... Fortified foods provide most of the vitamin D in American diets." The link has a table of vitamin D content for foods. Almost all the U.S. milk supply and many plant milks are fortified with vitamin D.

Cost

One study pointed out: "In 2014, vitamin D levels were the fifth most common laboratory test ordered for Medicare patients, with a total cost of $323 million." This adds up to many billions of dollars every decade for mostly unnecessary testing for vitamin D.

We consumers buy vitamin D supplements that cost much more. According to one report, over $35 billion is spent on all supplements. For most healthy adults under 75, this may be a waste of money.