Vitamin and Mineral Supplementation

Mamas on Bedrest: Link Found Between Vitamin D and Gestational Diabetes

October 19th, 2012

Mamas, do you know your vitamin D level? Recent research suggests that if you are deficient in vitamin D early on in pregnancy, you are at risk for developing gestational diabetes.

At the the European Association for the Study of Diabetes (EASD) 48th Annual Meeting in Berlin Germany, Marilyn Lacroix, a master’s degree candidate from the Faculty of Medicine and Health Sciences at the University of Sherbrooke in Quebec, Canada reported that women with lower serum levels of vitamin D during the first trimester of pregnancy are at greater risk for developing gestational diabetes mellitus (GDM) later in pregnancy.

Study Design

According to Lacroix’s research, the association between vitamin D level and GDM risk was independent of age, season of blood sampling, vitamin D supplementation, and adiposity (fatness) of the mother. Women aged 18 years or older (n = 655) who were in their sixth to 13th week of pregnancy and in good health were recruited from the Sherbrooke area in Canada, which lies at about 45 degrees north latitude and therefore gets relatively less sun exposure than more southerly locations. The researchers made anthropometric (fat determination) measurements and determined 25OHD (Vitamin D) levels at the time of recruitment. Between the 24th and 28th weeks of pregnancy, they performed a 75-g fasting oral glucose tolerance test (OGTT) to determine normal glucose tolerance or GDM according to criteria of the International Association of the Diabetes and Pregnancy Study Groups (fasting glucose ≥ 5.1 mmol/L; 1 hour post-OGTT glucose ≥ 10.0 mmol/L; 2-h post-OGTT glucose ≥ 8.5 mmol/L)

Results

54 women, 8.2% of the study population developed GDM. These women were on average older and had larger waist circumferences  than their cohorts. According to Lacroix,

“The mean total 25OHD levels in our cohort was about 63 nmol/L, and participants with gestational diabetes mellitus had lower levels of 25OHD compared to [women with] normal glucose tolerance,” Lacroix reported. “The overall prevalence of vitamin D deficiency in our cohort was about 27%.”

Lower levels of Vitamin D were associated with an increased risk of incident GDM. When the data was adjusted for age, season of blood sampling, vitamin D supplementation, and waist circumference, the risk for GDM increased by 40% for each standard deviation (SD) decrease in Vitamin D level. Translation, for each decrease in Vitamin D by 18.8nmol/L, the risk for developing GDM increased 40%.  This result was consistent regardless of the measurement of adiposity used (waist circumference, body mass index, or percentage body fat). At these second trimester measurements, women with GDM also had lower insulin sensitivity. Lacroix also noted that women with lower levels of Vitamin D, higher waist circumference and lower insulin sensitivity also had lower B cell compensation. B cells are the insulin producing cells in the pancreas. However, B cell compensation was found to be independent of Vitamin D level.

Overall,  Lacroix and her colleagues concluded that lower vitamin D levels in the first trimester are associated with increased risk of developing GDM, independent of age, season of blood sampling, vitamin D supplementation, and adiposity measurements. Lower vitamin D levels are associated with insulin resistance but not with insulin secretion or β cell compensation after adjustment for confounders.

Discussion at the meeting

Anne Dornhorst, BM, BCh, from the Department of Diabetes and Endocrinology at Imperial College Healthcare NHS Trust in London, United Kingdom, commented,

“If you take women from sub-Saharan Africa and Muslim women who are not only dark skinned but covered, you can say to yourself, is there any point measuring it? Just give them vitamin D.

She said also that blacks are at high risk for type 2 diabetes and gestational diabetes. Indians, too, have a very high level of vitamin D deficiency along with a high level of type 2 and gestational diabetes.

As of publication of the Abstract at the (EASD) 48th Annual Meeting October 3, 2012, there currently isn’t a recommended amount of Vitamin D for supplementation.

Other Research

Dr. Edward Giovannucci, nutrition researcher at the Harvard School of Public Health has studied Vitamin D extensively. He states,

“Throughout most of human evolution,” Dr. Giovannucci wrote, “when the vitamin D system was developing, the ‘natural’ level of 25-hydroxyvitamin D was probably around 50 nanograms per milliliter or higher. In modern societies, few people attain such high levels.”

People in colder regions form their year’s supply of natural vitamin D in summer, when ultraviolet-B rays are most direct. But the less sun exposure, the darker a person’s skin and the more sunscreen used, the less pre-vitamin D is formed and the lower the serum levels of the vitamin. People who are sun-phobic, babies who are exclusively breast-fed, the elderly and those living in nursing homes are particularly at risk of a serious vitamin D deficiency. The main dietary sources are wild-caught oily fish (salmon, mackerel, bluefish, and canned tuna) and fortified milk and baby formula, cereal and orange juice, yet experts say it is rarely possible to consume adequate amounts through foods.

Dr. Michael Holick of Boston University, a leading expert on vitamin D and author of “The Vitamin D Solution” (Hudson Street Press, 2010), said in an interview,

“We want everyone to be above 30 nanograms per milliliter, but currently in the United States, Caucasians average 18 to 22 nanograms and African-Americans average 13 to 15 nanograms.” African-American women are 10 times as likely to have levels at or below 15 nanograms as white women, the third National Health and Nutrition Examination Survey found.”

Recommendations

The current recommended intake of vitamin D, established by the Institute of Medicine, is 200 I.U. a day from birth to age 50 (including pregnant women); 400 for adults aged 50 to 70; and 600 for those older than 70. Dr. Holick, among others, recommends a daily supplement of 1,000 to 2,000 units for all sun-deprived individuals, pregnant and lactating women, and adults older than 50. The American Academy of Pediatrics recommends that breast-fed infants receive a daily supplement of 400 units until they are weaned and consuming a quart or more each day of fortified milk or formula.

But both Dr. Giovannucci and Dr. Holick say it is very hard to reach such toxic levels. Healthy adults have taken 10,000 I.U. a day for six months or longer with no adverse effects. People with a serious vitamin D deficiency are often prescribed weekly doses of 50,000 units until the problem is corrected. To minimize the risk of any long-term toxicity, these experts recommend that adults take a daily supplement of 1,000 to 2,000 units.

Implications for Mamas on Bedrest

I don’t know about any of you, but my Vitamin D levels were not measured either time that I was pregnant. In fact, they were only measured recently when I was seeing a gynecologists for hormonal imbalances related to perimenopause. Given the significance of vitamin D deficiency and its link to GDM, I hope that OB’s will begin screening for this very important vitamin and replacing it accordingly.

However, Vitamin D deficiency can have even farther reaching, more deleterious effects for mamas on bed rest. Vitamin D is important in calcium metabolism and bone formation. Judy Maloni, PhD has done extensive research on the effects of bed rest. She notes that in as little as 2 weeks, women on bed rest begin losing bone mass. So if women on bed rest are already at risk for bone loss, coupling that with low levels of Vitamin D only makes them at greater risk. While Bedrest is often a necessity, we can at least fight back against GDM and bone loss by providing adequate vitamin D supplementation. As Drs. Giovannucci and Holick have both stated, our diets and many of our supplements (speaking about prenatal vitamins here!) don’t provide adequate vitamin D supplementation.

Speak with your healthcare provider about the importance of Vitamin D and whether or not you need supplementation. If you have questions about how to go about finding a good Vitamin D supplement, e-mail us at info@mamasonbedrest.com.

References

MedScape News: OB/GYN & Women’s Health. “Low First-Trimester Vitamin D Predicts Gestational Diabetes” Marilyn Lacroix, Master’s Degree candidate from the Faculty of Medicine and Health Sciences at the University of Sherbrooke in Quebec, Canada. Presented at European Association for the Study of Diabetes (EASD) 48th Annual Meeting. Abstract 82. Presented October 3, 2012.

What Do You Lack? Probably Vitamin D-The New York Times

Astronauts and Pregnancy Bed Rest: What NASA is teaching us about inactivity Judith A Maloni, PhD, FAAN

Antepartum Bed Rest For Pregnancy Complications: Efficacy and Safety for Preventing Preterm Birth-Judith A Maloni, PhD, FAAN