Prevention of Rickets and Vitamin D Deficiency: New Guidelines for Vitamin D Intake

BACKGROUND

Cases of rickets in infants attributable to inadequate vitamin D intake and decreased exposure to sunlight continue to be reported in the United States.^1–3 Rickets is an example of extreme vitamin D deficiency. A state of deficiency occurs months before rickets is obvious on physical examination. The new recommended adequate intake of vitamin D by the National Academy of Sciences (NAS) to prevent vitamin D deficiency in normal infants, children, and adolescents is 200 IU per day.⁴ This differs from the 400 IU per day that has been recommended in previous editions of the Pediatric Nutrition Handbook of the American Academy of Pediatrics (AAP). The new NAS guidelines for infants are based on data primarily from the United States, Norway, and China, which show that an intake of at least 200 IU per day of vitamin D will prevent physical signs of vitamin D deficiency and maintain serum 25-hydroxy-vitamin D at or above 27.5 nmol/L (11 ng/mL). Although there are generally less data available for older children and adolescents, the NAS has come to the same conclusions for this population.⁴ Also, it is acknowledged that most vitamin D in older children and adolescents is supplied by sunlight exposure.⁴ However, dermatologists and cancer experts advise caution in exposure to sun, especially in childhood, and recommend regular use of sunscreens.^5–11 Sunscreens markedly decrease vitamin D production in the skin.

SUNLIGHT EXPOSURE

A potential source of vitamin D is synthesis in the skin from the ultraviolet B light fraction of sunlight. Decreased sunlight exposure occurs during the winter and other seasons and when sunlight is attenuated by clouds, air pollution, or the environment (eg, shade). Lifestyles or cultural practices that decrease time spent outdoors or increase the amount of body surface area covered by clothing when outdoors further limit sunlight exposure. The effects of sunlight exposure on vitamin D synthesis are also decreased for individuals with darker skin pigmentation and by the use of sunscreens.⁵ All of these factors make it very difficult to determine what is adequate sunshine exposure for any given infant or child. Furthermore, the Centers for Disease Control and Prevention, with the support of many organizations including the AAP and the American Cancer Society, has recently launched a major public health campaign to decrease the incidence of skin cancer by urging people to limit exposure to ultraviolet light.⁶ Indirect epidemiologic evidence now suggests the age at which direct sunlight exposure is initiated is even more important than the total sunlight exposure over a lifetime in determining the risk of skin cancer.^7–11 Thus, guidelines for decreasing exposure include directives from the AAP that infants younger than 6 months should be kept out of direct sunlight, children’s activities that minimize sunlight exposure should be selected, and protective clothing as well as sunscreens should be used.¹¹

BREASTFEEDING AND VITAMIN D

Infants who are breastfed but do not receive supplemental vitamin D or adequate sunlight exposure are at increased risk of developing vitamin D deficiency or rickets.^1–3,12,13 Human milk typically contains a vitamin D concentration of 25 IU/L or less.^14–16 Thus, the recommended adequate intake of vitamin D cannot be met with human milk as the sole source of vitamin D for the breastfeeding infant. Although there is evidence that limited sunlight exposure prevents rickets in many breastfed infants,^17,18 in light of growing concerns about sunlight and skin cancer and the various factors that negatively affect sunlight exposure, it seems prudent to recommend that all breastfed infants be given supplemental vitamin D. Supplementation should begin within the first 2 months of life. As noted above, it is very difficult to determine what is adequate sunlight exposure for an individual breastfed infant. Additional research is suggested to more fully understand the factors underlying the development of vitamin D deficiency and rickets in some breastfed infants.

FORMULAS AND VITAMIN D

All infant formulas sold in the United States must have a minimum vitamin D concentration of 40 IU/100 kcal (258 IU/L of a 20-kcal/oz formula) and a maximum vitamin D concentration of 100 IU/100 kcal (666 IU/L of a 20-kcal/oz formula).¹⁹ All formulas sold in the United States actually have at least 400 IU/L.²⁰ Thus, if an infant is ingesting at least 500 mL per day of formula (vitamin D concentration of 400 IU/L), he or she will receive the recommended vitamin D intake of 200 IU per day.

VITAMIN D SUPPLEMENTS

If the intake of vitamin D-fortified milk or formula is less than 500 mL per day, a vitamin D supplement can be provided by currently available multivitamin preparations containing 400 IU of vitamin D per mL or tablet. Currently available solitary vitamin D preparations (containing up to 8000 IU/mL) are too concentrated to be safe for routine home use. It is important that special efforts be directed toward supplementing populations at increased risk of developing rickets and vitamin D deficiency, including those with increased skin pigmentation and decreased sunlight exposure.

SUMMARY

To prevent rickets and vitamin D deficiency in healthy infants and children and acknowledging that adequate sunlight exposure is difficult to determine, we reaffirm the adequate intake of 200 IU per day of vitamin D by the National Academy of Sciences⁴ and recommend a supplement of 200 IU per day for the following:

1. All breastfed infants unless they are weaned to at least 500 mL per day of vitamin D-fortified formula or milk.

2. All nonbreastfed infants who are ingesting less than 500 mL per day of vitamin D-fortified formula or milk.

3. Children and adolescents who do not get regular sunlight exposure, do not ingest at least 500 mL per day of vitamin D-fortified milk, or do not take a daily multivitamin supplement containing at least 200 IU of vitamin D.

Section on Breastfeeding, 2002–2003

Lawrence M. Gartner, MD, Chairperson

Linda S. Black, MD

Ruth A. Lawrence, MD

Audrey J. Naylor, MD, DrPH

Donna O’Hare, MD

Richard J. Schanler, MD

Arthur I. Eidelman, MD

Policy Committee Chairperson

Liaisons

Alice Lenihan, MPH, RD, LDN

National WIC Association

John Queenan, MD

American College of Obstetricians and Gynecologists

Staff

Betty Crase, IBCLC

Committee on Nutrition, 2002–2003

Nancy F. Krebs, MD, Chairperson

Robert D. Baker, Jr, MD, PhD

Frank R. Greer, MD

Melvin B. Heyman, MD

Tom Jaksic, MD, PhD

Fima Lifshitz, MD

Liaisons

Donna Blum-Kemelor, MS, RD

US Department of Agriculture

Margaret Patricia Boland, MD

Canadian Paediatric Society

William Dietz, MD, PhD

Centers for Disease Control and Prevention

Van S. Hubbard, MD, PhD

National Institute of Diabetes and Digestive and Kidney Diseases and National Institutes of Health

Elizabeth Yetley, PhD

US Food and Drug Administration

Consultant

Susan Baker, MD, PhD

Staff

Pamela Kanda, MPH