Why You Need Vitamin D During Pregnancy
Even in sunny West Texas where I live, obstetricians tell me that many pregnant women are vitamin D deficient or insufficient. Why? In this post, I flush out the whys and hows of vitamin D deficiency and how to get enough.
Who is D Deficient?
It’s possible that many of us are walking around with a vitamin D deficiency. The best source of vitamin D is sunlight; your skin produces its own vitamin D when exposed to sufficient sun. However, between fear of skin cancer and other factors, it seems that few of us actually get the sun exposure we need to make enough D. The factors below can all have an effect:
- Amount of skin exposed
- Type of clothing: some clothing blocks more UV rays than others
- Time spent in the sun
- Use of sunscreen
- Pigmentation of the skin: Dark skinned people may need up to 10 times the sun exposure to produce the same amount of vitamin D
- Larger body mass—more body fat increases need for vitamin D
- Latitude: People who live in northern latitudes (above latitude of 40) and southern latitudes (below latitude of 40) are at risk for vitamin D deficiency because the amount of sunshine in winter months makes vitamin D production impossible.
- Amount of pollution: smog blocks some UV rays
What Happens if You don’t Get Enough?
Recent research shows that vitamin D—which is actually converted to a hormone in the body, is responsible for a lot more than calcium status and bone density—it appears to affect all organ systems. Current research indicates vitamin D deficiency could play a role in causing many types of cancer. Some studies also show associations between vitamin D deficiency and risk of heart disease, stroke, hypertension, autoimmune diseases, diabetes, depression, chronic pain, osteoarthritis, osteoporosis, muscle weakness, muscle wasting, birth defects, and periodontal disease.
Lack of the vitamin during pregnancy and infancy can have negative effects on bone development but may also affect the development of type 1 diabetes. In one study, increasing vitamin D intake during pregnancy reduced the long-term risk of type 1 diabetes by 80% in their infants. A recent analysis of 16 studies concluded that, vitamin D supplementation during pregnancy may decrease the risk of pre-eclampsia, low birthweight and preterm birth.
How Much D Do You Need?
Many researchers agree that the current Dietary Reference Intake for D is underestimated. Dr. Michael Holick, a researcher from Boston University’s Vitamin D, Skin, and Bone Research Laboratory, suggests that pregnant and breastfeeding women need 1,000-2,000 IU of daily vitamin D from diet or supplements when vitamin D production from sun exposure is inadequate. The suggested Dietary Reference Intake for Vitamin D is 600 IU. The Tolerable Upper Intake of Vitamin D for adults is 4,000 IU.
How to Get Enough D—A Balance of Sun and Supplements
It’s tough to balance getting vitamin D from the sun vs. your risk of skin cancer. The Skin Cancer Foundation promotes getting your vitamin D from sun exposure while using a sunscreen of at least SPF 15 and the rest from foods and supplements. The Cancer Council in Australia recommends using sunscreen if the UV Index is over 3. Here are some tips:
How much incidental sun exposure do you get?
If you are fair skinned, you only need a “few minutes” of summer sun on the face, arms and hands (or equivalent exposure) to get some vitamin D. Dark skinned women could need up to 10 times as much per day to produce the same amount. According to the Skin Cancer Foundation, it only takes a few minutes of sun for the UV rays to damage DNA. And of course the sun also causes premature skin aging…hello freckles, dark spots and wrinkles!
Winter: Sun exposure is drastically reduced depending on climate and latitude. In many cities, there is not enough winter sunshine to allow adequate vitamin D production—even if you were brave enough to have some of your skin uncovered!! If you have adequate sun exposure in summer months, that can carry you a month or two into the winter. Most people will need supplements in the winter (and in the summer too.)
How Much Vitamin D do You Get from Food?
Very few foods are naturally high in vitamin D. While most milk is fortified with it, milk products like cheese and yogurt are generally not.
VITAMIN D CONTENT OF FOOD
How Can You Tell if You’re Deficient?
It’s wise to get your vitamin D: 25(OH)D level checked, especially if you don’t see much sun, you have dark skin or you live at a northern latitude. A few studies have shown that even when women took a prenatal vitamin with 400 IU of vitamin D, drank milk and ate fish regularly, 73% of the women and 80% of their infants were considered vitamin D deficient. If your health care provider doesn’t do it on your first visit, ask her to do it on your second one.
- Vitamin D Council. Health Conditions 2018. Available from: vitamindcouncil.org/health-conditions
- Hypponen E, Laara E, Reunanen A, Jarvelin M-R, Virtanen SM. Intake of vitamin D and risk of type 1 diabetes: a birthcohort study. Lancet 2001;358:1500-3.
- Skin Cancer Foundation
- Holick MF. Vitamin D Deficiency. New England Journal of Medicine. 2007;357: 266-81
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