The Recommended Dietary Allowance (RDA) for Vitamin D is currently set at 600–800 IU/day (15–20 mcg) for adults. Fortified milk typically provides 100 IU per 8 oz serving (236 mL). So while milk can provide a good amount of vitamin D it may not be sufficient to ensure adequate daily intakes.
In fact, adults who rely on food sources alone for vitamin D may only be getting half their daily vitamin D requirement on average. Those who take a vitamin D supplement are much more likely to achieve the RDA.
Doses higher than the RDA may be warranted in cases of deficiency, non-response at lower dosages, or in those with a BMI >30. In these cases, a 1,000–2,000 IU/day (25–50 mcg) dose (or greater) of vitamin D may be necessary.
So, unless you are drinking 6+ glasses of milk a day, consuming other vitamin D rich foods (fatty fish, egg yolks) or considering supplementation will be required.
- Dietary Reference Intakes for Calcium and Vitamin D. .
- Foods, fortificants, and supplements: Where do Americans get their nutrients?. J Nutr. (2011) Fulgoni VL 3rd, et al.
- Contribution of Dietary Supplements to Nutritional Adequacy in Various Adult Age Groups. Nutrients. (2017) Blumberg JB, et al.
- Vitamin D intakes of adults differ by income, gender and race/ethnicity in the U.S.A., 2007 to 2010. Public Health Nutr. (2014) Moore CE, Radcliffe JD, Liu Y.
- Vitamin D supplementation, body weight and human serum 25-hydroxyvitamin D response: a systematic review. Eur J Nutr. (2014) Zittermann A, et al.
- Vitamin D deficiency in adults: when to test and how to treat. Mayo Clin Proc. (2010) Kennel KA, Drake MT, Hurley DL.
- Recognition and management of vitamin D deficiency. Am Fam Physician. (2009) Bordelon P, Ghetu MV, Langan RC.