By, Rachel Neifeld, RD, CDN
Known for its role in maintaining bone health by facilitating calcium absorption in the intestine, vitamin D also acts as a hormone in the body and affects the growth and differentiation of many different types of cells. Vitamin D can be obtained through sunlight, some foods, and in supplement form. All of the important roles that vitamin D plays in the body are not yet known, but when it comes to body weight, new studies are shedding more light on the sunshine vitamin.
A new study published in the Journal of Clinical Nutrition found that children were more likely to be overweight if their mothers had lower levels of vitamin D during pregnancy. Interestingly, children of women with low levels of vitamin D were leaner at birth but had more body fat at age six than those born to moms with higher levels during pregnancy. The researchers stated, “… there could be programmed effects on the fetus arising from a lack of maternal vitamin D that remain with the baby and predispose him or her to gain excess body fat in later childhood,” and noted that taking vitamin D supplements in late pregnancy was important in preventing deficiency.
Further linking vitamin D with weight status, another study conducted by researchers from the Kaiser Permanente Center for Health Research in Portland, Oregon found that over a five year period, women aged 65 and older with low levels of vitamin D gained about two more pounds than those with higher levels. At the beginning of the study, women with low levels of vitamin D actually weighed more to begin with. The women with insufficient vitamin D levels gained 18.5 pounds over five years whereas women with normal levels gained 16.4 pounds during the study period. The researchers suggest that the women may be experiencing chronic weight gain due to lack of sunlight exposure as modern societies move indoors.
It is recommended that the general population, including pregnant and lactating women, get 600 IU of vitamin D each day. Women taking prenatal vitamins should include vitamin D –rich foods in their daily diets as prenatal vitamins contain only 400 IU of vitamin D.
Sufficient vitamin D can be obtained by exposing the face, arms, legs, or back to the sun between 10 am and 3 pm for approximately 5–30 minutes twice a week, but be sure to apply sunscreen at all other times to prevent the cancer-promoting effects of UV rays.
Fortunately, it isn’t necessary to be exposed to UV rays to obtain “the sunshine vitamin.” A serving of salmon, swordfish, or cod liver oil will provide greater than one hundred percent of the daily value for vitamin D. Tuna and mackerel are also good seafood sources of the vitamin, though pregnant women should avoid king mackerel and swordfish as they are high in mercury, and when eating tuna choose “chunk light” and limit to six 6-oz servings per month. Other good sources of vitamin D include egg yolks, cheese, and fortified orange juice, milk, yogurt, and cereals.