ResearchM ilk is an important source of vitamin D, calcium, riboflavin, protein and energy during pregnancy, yet many women choose or are advised to avoid drinking milk for a variety of reasons, including the prevention of allergies in their children.1 Limiting milk intake compromises the quality of the maternal diet; 2-5 women who avoid milk may not obtain adequate levels of vitamin D, calcium, protein or riboflavin. Milk restriction is a risk factor for pregnancy-associated hypertension.6 Low vitamin D intake is associated with neonatal rickets 7 and decreased birth weight.
8Inadequate consumption of riboflavin is associated with decreases in weight, 9 length and head circumference of babies at birth.
10Although most nutrients in milk may be replaced from other foods or with supplements, vitamin D is found in few commonly consumed foods except for milk fortified with the vitamin.11 Dermal conversion of the precursor cholecalciferol to activated vitamin D is a seasonally unreliable source, particularly when the exposure of skin to sunlight is limited,
12and may not compensate for low nutritional intake. Under optimal conditions, 15 minutes of daily exposure of the hands and face to sun is required to produce adequate vitamin D, 13 but this conversion is reduced by the prolonged winter season at more polar latitudes, 14,15 by use of sunscreens with a sun protection factor (SPF) above 8, 16 and by ozone air pollution.
13People whose skin pigmentation is dark are more vulnerable than others to insufficient vitamin D conversion.
16In this study we compared the birth weight, crown-heel length and head circumference of newborns whose mothers restricted their intake of milk during pregnancy with the babies of those who did not.
MethodsBetween May 1997 and June 1999 we screened 2091 women who attended prenatal classes at 3 hospitals in Calgary, Alberta. The study was approved by the Institutional Review Board of McGill University as well as by the Calgary Health Region Ethics Board.Women were given an anonymous questionnaire that asked whether they would be willing to participate in an indepth study on dietary intake and pregnancy outcomes, and if they restricted dairy products for any reason. For consenting participants, a second questionnaire asked for demographic data, lifestyle characteristics (e.g., smoking habits, highest level of education achieved) and if they had certain metabolic conditions (e.g., diabetes, hypertension) or a multiple pregnancy. Only healthy mothers with singleton pregnancies were
Association of low intake of milk and vitamin D during pregnancy with decreased birth weightB Ba ac ck kg gr ro ou un nd d: : Some pregnant women may be advised or choose to restrict milk consumption and may not take appropriate supplements. We hypothesized that maternal milk restriction during pregnancy, which can reduce intakes of protein, calcium, riboflavin and vitamin D, might represent a health risk by lowering infant birth weight. M Me et th ho od ds s: : We screened women between the ages of 19 and 45 years...