Common Questions
What are the dietary sources of vitamin D?
Only a few natural foods, such as fatty fish, cod liver oil, and egg yolks, contain some vitamin D. Fortified foods, including milk, cereal, margarine, and butter, are the major dietary sources of vitamin D in developed countries. Unfortunately, even fortified foods do not necessarily contain the amount of vitamin D listed on the label. One study found that up to 70 percent of milk samples in North America did not contain the 400 IU per quart as stated on the label (1). The dietary intake can vary enormously between individuals. One study of 333 women showed intake of vitamin D to vary from 20 IU to more than 1,600 IU/day (2).
Dietary intake and intestinal absorption of vitamin D remain relatively unchanged as one ages (3). However, vitamin D is absorbed in the jejunum and upper ileum, and any disorder that affects this part of the gastrointestinal tract could affect vitamin D absorption.
The Institute of Medicine (4) created the following dietary recommendations for daily vitamin D intake (in the absence of adequate sunlight), however, most experts today feel that these are too low:
| Population Group | Daily Intake |
|---|---|
| Birth to age 50 | 200 IU |
| Age 51 to 70 | 400 IU |
| Age 70 and over | 600 IU |
| Homebound/institutionalized elderly* | 800 IU |
* Some experts feel that most adults need at least 1,000 IU per day (5). The above recommnedations are being revised and should be available in May of 2010.
- Holick MF, Shao Q, Liu WW, Chen TC. The vitamin D content of fortified milk and infant formula.. N Engl J Med 1992; 326: 1178-1181.
- Krall EA, Sahyoun N, Tannenbaum S, Dallal GE, Dawson-Hughs B. Effect of vitamin D intake on seasonal variations on parathyroid hormone secretion in postmenopausal women. N Engl J Med 1989; 321: 1777-1783.
- Clemens TL, Zhou XY, Mykles M, Endres D, Lindsay R. Serum vitamin D3 and vitamin D2 concentrations and absorption of vitamin D2 in elderly subjects. J Clin Endocrinol Metab 1986; 63: 656-660.
- Standing Committee on the Scientific Evaluation of Dietary Reference Dietary reference intakes: calcium, phosphorous, magnesium, vitamin D and fluoride.. Intakes, Institute of Medicine. 1997.
- Holick MF. McCollum Award Lecture, Vitamin D-New horizons for the 21st century. Am J Clin Nutr 1994; 60: 619-630.