Current guidelines for daily vitamin D intake during pregnancy range from 200 international units (IU) per day to 400iu. For decades, doctors have worried that too much vitamin D during pregnancy could harm the mother and baby but growing research is proving pregnant women require more and not less sun.
The vast majority of our knowledge of the impact and importance of vitamin D has come from research within the last decade. Vitamin D is not only essential during pregnancy, research now states that supplementing with 1,000iu daily or more may actually reduce the risk of complications (1). A baby is born with around 50-60% of the Mother’s vitamin D levels (2). If the Mother is deficient then so will the baby. It has been proven that babies born in Spring have a higher propensity for illness than those born in Autumn, the reason being the Mother’s exposure, or lack of it, to sunlight.
A well referenced study looked at women in their second trimester and beyond. In the study, 500 women who were at least 12 weeks pregnant took either 400iu, 1,000iu, or 4,000iu of vitamin D per day. The women who took 1,000iu and 4,000iu were least likely to go into labour early, give birth prematurely, or develop infections.
“Pregnant women need to take at least 1,000iu of vitamin D a day,” says Dr Bruce Hollis, Director of paediatric nutritional sciences at the Medical University of South Carolina and one of the authors of the study. “The ideal would be 4,000iu. In the higher dosage groups we didn’t see a single adverse effect. It was absolutely safe, and we saw a lot of improved outcomes. The risk of preterm labour was vastly decreased and so was the risk of other complications of pregnancy.”
Taking supplements is the only practical way to consume that much vitamin D as to rely on food as a way of ensuring our daily amount is simply not feasible for our modern diets and lifestyles. A glass of milk delivers around 5iu, two eggs will give you 40iu and a portion of cheese around 50iu. Wild salmon is a good source providing around 500iu within a decent portion. However if the salmon is from a farmed source that quantity reduces dramatically to around 100iu!
Exposure to direct and unprotected sunlight is the most effective way of achieving our required levels but this is proving difficult as our modern lives keep us inside for longer periods of time. Add to this the fact that the UK is one of the cloudiest countries in the industrialised world. What we fail to remember is that our bodies only begin to store vitamin D at a blood level of 40ng/ml. The average blood level in Britain during Summer months is only 32ng/ml with Winter averaging on 19ng/ml! (4, 5)
“There are no risks,” Hollis adds, “as the conventional wisdom about the dangers of too much vitamin D was manufactured and based on flawed data”. “There was never any real harm, just misconceptions.”
Michael F. Holick, M.D., a professor of medicine, physiology, and biophysics at the Boston University School of Medicine, has maintained for years that getting too little vitamin D is worse than getting too much. Although doctors have been taught that vitamin D is toxic in large amounts, he says, vitamin D intoxication is extremely rare and easy to treat. The levels of vitamin D recommended in the study are sensible, Holick says. Previous research suggests that pregnant women who get too little vitamin D are more likely to develop high blood pressure and muscle cramping, he says. “Giving 4,000 IU a day to pregnant women not only doesn’t cause toxicity, but may improve birth outcomes,” Holick says. “The risks of vitamin D during pregnancy are overblown and the benefits are understated.” (5)
Prompted by the recent flood of research on vitamin D deficiency, the Institute of Medicine, an independent organization that advises the U.S. Government on health matters, is now considering whether to raise its guidelines for vitamin D intake, including those for pregnant women (currently 200iu per day) and the maximum safe daily dose (currently at 2,000iu). The new guidelines are expected to be announced in 2012/13.
Written by Andrew Thomas from BetterYou
1, 5: Randomized comparison of the effects of the vitamin D3 adequate intake verus 100mcg (4,000iu) per day on biochemical responses and the wellbeing of patients. R Vieth, S Kimball, A Hu, PG Walfish. July 2004.
2: Sunlight Robbery – Health benefits of sunlight are denied by current public health policy in the UK. Oliver Gillie. A report presented at The House of Commons, November 2005.
3: Assessment of dietary vitamin D requirements during pregnancy and lactation. BW Hollis, CL Wagner, Medical University of South Carolina, American Journal of Clinical Nutrition, May 2004.
4: Zittermann, A., Scheld, K., and Stehle, P., Seasonal variations in vitamin D status and calcium absorption influence bone turnover in young women. European Journal of Clinical Nutrition, 1998. 52: p501-506.
5: Sunlight Robbery. Oliver Gillie, Health Research Forum, 2004.