Recommendations Regarding Vitamin D Intake in Osteogenesis Imperfecta

Function

Vitamin D functions as a hormone in the body to promote adequate calcium absorption from the intestine and to facilitate normal mineralization of bone. Most of our vitamin D comes from the skin, using UV light from the sun to synthesize the vitamin. Individuals not getting adequate sunlight daily, African Americans and persons living in northern climates may become vitamin D deficient. Vitamin D has been found to improve the function of other body systems. Deficiency is associated with abnormal bone mineralization, muscle weakness, altered immune status, impaired glucose metabolism as occurs in diabetes mellitus, and the risk of certain malignancies such as colorectal cancer, breast and prostate cancers.

Background

The definition of adequate dietary intake and adequate serum levels for vitamin D [25-hydroxy vitamin D, or 25(OH)D] is currently under consideration. 25(OH) D levels are measured in a blood sample. The recommended blood levels for children and adults have been increased from a previous level of 20 ng/ml to a level of between 32 and 60 ng/ml in several recent studies (Roth). At 32-60 ng/ml, intestinal calcium absorption and the levels of parathyroid hormone and alkaline phosphatase, both bone-active proteins, will be in the normal range, indicating an optimal setting for calcium metabolism in most people.

Vitamin D is available as either the D-2 form or ergocalciferol (plant derived) or the D-3 form, cholecalciferol, which is animal derived. Initial studies indicate that the D-3 form may be more effective in humans (Armas ). However, vitamin D-3 is not as commercially available as is the D-2 form.

Because of widely different age-related heights and body weights among individuals with OI, we propose that vitamin D-3 intake be based on body weight rather than on age. Note that the Food and Nutrition Board (1997) currently recommends 200 IU/day for ages 0-50 years, and 400 IU/day for ages 51-70 years (Dietary Reference Intake). Over age 70 the recommendation is for 600 IU daily. Several investigators (see references below), suggest that the daily intake at the 400-600 IU level for adults is not adequate to maintain optimal serum 25(OH) D levels at, or above, the recommended 32-60 ng/ml level, or to maintain normal parathyroid hormone or bone alkaline phosphatase levels, and by inference, normal calcium metabolism. Roth (Canada) observed that vitamin D deficiency was common in children and reported that a minimum intake of 18 International Units per 2.2 lbs per day was needed to bring serum 25(OH)D levels into the low normal range.

Recommendation:

In the absence of large-scale studies examining the amount of daily vitamin D required to raise individual serum 25-hydroxy vitamin D to 32-60 ng/ml, we propose a range of daily vitamin D intake of: 13- 18 IU/lb/ or 0.75 to 1.0 micrograms/kg/day.

These doses are approximately 2-4 times greater than the Dietary Reference Intakes recommended by the Food and Nutrition Board, National Academy of Sciences (NAS) in 1997. The tolerable upper limit recommended by NAS is 1000IU/day for children age 0-1 and 2000IU/d for all other ages. However the 2000 IU daily limit has been doubled in certain studies without producing excessive increases in serum 25(OH)D levels (Veith).

Vitamin D-3 Intake

Approximate Weight	IU/day	Micrograms/day
50 lbs - 20 kg	600 - 800	15-20
90 lbs - 40 kg	1100-1600	30-40
110 lbs - 50 kg	1200-2000	37-50
150 lbs - 70 kg and above	2000-2800	50-70

*Vitamin D diet supplements are measured in International Units (IU) or as micrograms. 1 microgram = 40 international units. 1 kilogram = 2.2 lbs

Therefore, it is emphasized that persons adopting these proposed doses:

• must do so with their physicians knowledge
• must monitor serum vitamin D levels 2 months after starting the above doses
• must monitor serum vitamin D at 4 month intervals thereafter, until stables serum values in the 32ng/ml to 60 ng/ml range are achieved.
• The vitamin D dose may then be increased or decreased with supervision to achieve a stable blood level.

*A small number of individuals with OI may have elevated urine calcium (hypercalcicuria), and some persons form kidney stones. In these cases, excess vitamin D or excess calcium intake is not warranted.

Please contact your physician or the following e-mail addresses for additional information:

• Jay R. Shapiro, MD

• The OI Program
• Kennedy Krieger Institute
• 707 North Broadway, Baltimore MD 21205
• Email: shapiroj@kennedykrieger.org

• Eileen McMahon, MS, RD

• Department of Nutrition
• Kennedy Krieger Institute
• mcmahone@kennedykrieger.org

• Bruce W. Hollis, PhD

• Director of Pediatric Nutritional Sciences, Medical
• University of South Carolina
• hollisb@mcsc.edu

References:

Armas L, Hollis B, Heaney RP. Vitamin D2 is Much Less Effective than Vitamin D3 in Humans. J Clin Endo Metabol 2004, 89: 5387.

Hollis, B., W. Circulating 25-Hydroxyvitamin D Levels Indicative of Vitamin D Sufficiency: Implications for Establishing a New Effective Dietary Intake Recommendations for Vitamin D1. J. Nutr. 2005, 135: 317.

Roth DE, Martz P, Yeo R, Prosser C, Bell M, Jones AB. Are National Vitamin D Guidelines Sufficient to Maintain Adequate Blood Levels in Children ? Can J Public Health. 2005, 96: 443.

Veith R, Chan PC, McFarlane GD Efficacy and Safety of Vitamin D Intake Exceeding the Lowest Oberved Adverse Effect Level Am J Clin Nutr 2001,73: 288.

Veith, R. Why the Optimal Requirement for Vitamin D3 is Probably Much Higher Than What is Officially Recommended for Adults. J of Steroid Biochem Mol Biol 2004, 89-90:575-579.

Weaver CM, Fleet JC. Vitamin D requirements: Current and future Am J Clin Nutr 2004, 80: (suppl): 1735S.