When it comes to food, fortified milk and orange juice, as well as some kinds of mushroom and wild-caught fish contain small (as in, practically obsolete) amounts of vitamin D. In order to meet the recommended dietary allowance, (i.e., 600 IU for healthy adults, per the National Academies) one would have to drink more than six glasses of fortified milk a day, 12 whole eggs, or a 3.5-ounce serving of sockeye salmon, and experts agree—even that’s not enough to move the needle on vitamin D status and reach healthy levels.
As mentioned earlier vitamin D deficiency rates among adults average 42% nationwide, with 82% of Black Americans and nearly 70% of Latino Americans experiencing deficiency. Other research shows that between 93 and 100% of the U.S. population fails to consume even 400 IUs of vitamin D per day (i.e., 200 IU below the recommended daily amount—which, for the record, is still far from sufficient to achieve and maintain healthy vitamin D status).
With this in mind, Holick recommends all his patients take a vitamin D supplement daily, no matter the season. Drake agrees, stating the Linus Pauling Institute recommends generally healthy adults take 2,000 IU of supplemental vitamin D every day, but noting that reaching ideal blood levels of vitamin D (i.e., that coveted 50 ng/ml or above) may require an even higher dosage of supplementation.
mbg's vice president of scientific affairs, Ashley Jordan Ferira, Ph.D., RDN, breaks down exactly how much vitamin D we need to achieve healthy serum levels: "Pharmacokinetic research shows that it takes 100 IU of vitamin D to increase a normal-weight adult's serum D levels by about 10 ng/ml. So, that means that in order to achieve 50 ng/ml, you need 5,000 IU of vitamin D per day."
If you're trying to do some quick mental calculations to determine how many servings of milk, eggs, or fish you'd need to eat to consume 5,000 IU of vitamin D daily, we'll save you the trouble—it's a lot. Too much, one would be fair to argue. Simply put, daily vitamin D supplementation is the most effective way to reach sufficient vitamin D levels and maintain whole-body health.*
(Looking for a comprehensive supplement that will help you achieve sufficient vitamin D status? Check out our vitamin D supplement roundup.)