Did you know that Vitamin D deficiency (hypovitaminosis D) is considered to be a global health problem, and has been labeled “an ignored epidemic”? (2)

 

Not only this, but according to a research study, which was published in the European Journal of Clinical Nutrition, pregnant Irish women’s intake of the sunshine vitamin is far less than the recommended intake required for normal development of their children’s bones. (3)

A Dublin based study, published in 2013, divided the participants equally into winter and summer groups. The study concluded that in Dublin and other locations in northern latitudes, that the high prevalence of maternal Vitamin D deficiency during the winter months, may have detrimental effects on fetal skeletal growth. (1)

In a 2011 study carried out under Professor Fionnuala Mc Auliffe, at the UCD School of Medicine and Medical Science, the findings revealed that pregnant Irish women have an average dietary intake of Vitamin D that is 80% below the recommended levels. (3)

As a fetus is developing, he/she is entirely dependent on the mother’s supply of calcium. Vitamin D is required for normal calcium homeostasis and bone mineralization. (1)

 

How does Vitamin D deficiency potentially affect your unborn baby?

• During pregnancy Vitamin D deficiency can lead to reduced bone growth in your unborn baby.
• It can also lead to poor bone development during early childhood.
• In severe cases it can cause childhood rickets.
• Your baby may be smaller than average.
• He/she may have a lower birth weight.
• It has been linked to an increased incidence of diabetes.
• Your child may be at higher risk to develop allergies.
• There is a risk of neonatal hypocalcemia.
• Your child may have a higher risk of schizophrenia.
• There can be a higher disposition to autoimmune disease in later life.
• There may be brain development issues.
• You child could be more prone to acute lower respiratory infections.
• There can be a higher risk of HIV transmission.

During pregnancy Vitamin D deficiency can affect the mother in the following ways:

• Higher incidence of gestational diabetes.
• Higher risk of pre-eclampsia. (5)

Dublin Based Study 2013 – Pregnancy In Dark Winters: Implications For Fetal Bone Growth (1)

This entirely Dublin based study, which was published in January 2013, compared two groups of women and their infants.

A total of 60 women and their infants took part in the study, and they were divided equally into a summer and winter group. The conclusion of the study was that the high prevalence of maternal hypovitaminosis D during winter months in northern latitudes may have detrimental effects on fetal skeletal growth.

The women selected for the study were all Caucasian, over 18 years of age and had no underlying medical conditions. Dietary Vitamin D intake was assessed with a 3 day food diary, that the women recorded over a 3 day period, including a weekend day.

The best indicator of Vitamin D levels is 25-hydroxyvitamin D (250HD) concentrations. This study measured 250HD in early pregnancy, at 28 weeks and in cord blood at delivery. In many other studies the accuracy of the prevalence of Vitamin D deficiency has been limited by the reliance on one single 250HD assessment, at one point in pregnancy, as well as the effects of seasonal variations and the heterogeneity of the populations studied.

How this Dublin based study differed:

Heterogeneity (the quality of being diverse and not comparable in kind) – in this study all the women were healthy Caucasians living in Dublin.

Seasonal variations – the first group were the winter group. These women were recruited in early pregnancy in September/October. They gave birth in March/April. The second group, the summer group, were recruited in early pregnancy in March/April and gave birth in September/October.

250HD concentrations – to measure Vitamin D levels were taken in early pregnancy (on average between 14.3 + or – 2.6 weeks), at 28 weeks and at delivery, in fetal blood from the umbilical cord.

Fetal Anomaly Ultrasound – around 20 weeks’ gestation this routine scan was performed and fetal biometry was recorded. This included biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). Fetal biometry was assessed again ultrasonographically at 34 weeks’ gestation.

Summary of the study’s results:

When the winter group was tested in their first trimester, in September/October, 66.7% of them had sufficient Vitamin D and only 6.7% were at high risk of deficiency. When this group was tested at 28 weeks, in December/January, those with a sufficiency had dropped to 30% and the number at risk of deficiency had risen to 20%. When they delivered in March/April, the fetal blood from the umbilical cord showed only 3.3% with a sufficiency and 46.7% were at high risk of deficiency.

The summer group when tested in the first trimester, March/April, had only 10% with a sufficiency and 50% who were at high risk of deficiency. At 28 weeks this group had 53.3% with a sufficiency of Vitamin D and only 10% at risk of deficiency. At delivery the fetal blood sample showed that 13.3% still had a sufficiency and 43.3% were at a high risk of deficiency.

The high percentages in both groups, of high risk deficiency, reflect the fact that the developing fetus is entirely dependent on the Mother’s 250HD concentrations.
37 out of the 60 women were taking prenatal supplements. The mean 25OHD concentration of those taking prenatal supplements was statistically significantly higher in early pregnancy compared with those receiving no supplementation. However there was no statistical significant difference at 28 weeks’ gestation or in fetal blood at delivery.

There was no statistically significant association noted in either cohort between maternal and fetal 25OHD and infant birth weight, length, or head circumference.

Fetal biometry at 20 weeks’ gestation was statistically significantly greater for those with cord blood 25OHD above rather than below the median concentration. Additionally, the mean infant length at birth was statistically significantly shorter in those with a 25OHD concentration less than the median in early pregnancy (52.1 vs. 53.6 cm, P¼.04).

The study concluded that in Dublin and other locations in northern latitudes, that the high prevalence of maternal Vitamin D deficiency during the winter months, may have detrimental effects on fetal skeletal growth.

In June 2013, new research was published, which was carried out under Professor Declan Naughton, at London’s Kingston University. The study was carried out in collaboration with the Aristotle University, Thessaloniki, Greece.

This research has suggested that the incidence of Vitamin D deficiencies in babies, coming directly from their mothers, was not 19% as previous studies showed, but in fact as high as 56% – therefore the problem may be almost three times as grave as we thought.

The study was published in the Nutrition Journal (8) and it used a new measuring technique which has the ability to measure 8 different Vitamin D forms in greater detail.

The research that was carried out in Greece, at the Aristotle University, focused on 60 Greek mothers and their babies. Obviously these Greek women enjoy more hours of sunshine than their Irish or British counterparts, however the study showed that many of these Greek mothers had low levels of Vitamin D. This suggests that what they ate was of equal importance as a source of Vitamin D as sunshine. (9)

Research has demonstrated, to what degree, a particular gene, called RXRA, related to the action of Vitamin D, predicts the bone density of children at the age of 4.

The study led by Dr. Nicholas Harvey, at the University of Southampton’s MRC Lifecourse Epidemiology Unit, provides additional support for the importance of Vitamin D during pregnancy.

Researchers measured epigenetic marks at birth, by cells which were collected from the umbilical cord. (10) It was evident that those children who had less marking at the time of birth (less marking generally means greater gene activity), had greater bone density at 4 years of age. One of these epigenetic marks related to Vitamin D concentrations in the mother’s blood, in late pregnancy. Again it has been shown that a deficiency in Vitamin D can result in lower bone density in children, making it an area of concern.

The subject of how much Vitamin D is enough has been debatable for quite a while. The circulating 25OHD concentration sufficient to meet the physiological needs of humans is an ongoing subject of debate. (14)

Additionally both our changed lifestyle and the risk of skin cancer have made us less likely to spend time with our skin exposed to the sun. Many people follow the recommendations to use sun screen when they do spend time in the sun, but this reduces the absorption of Vitamin D.

Also over the years there have been scares regarding Vitamin D toxicity. However according to the Vitamin D Council (4) you would need to take 40,000 IU per day for a good few months or more to risk Vitamin D toxicity, or else take a massive one-time dose.
If you wish to understand some of the history of the debates around Vitamin D, this article is a good start:

The Vitamin D Debate

Traditionally Vitamin D Was Linked To Childhood Rickets

For a long time Vitamin D was linked primarily to childhood rickets and therefore it did not receive the attention it deserved in other areas. In more recent years this has changed.

Now Vitamin D deficiency has been linked to the progression of a range of serious disorders such as:(5) (13)

• Cancer
• Diabetes
• Hypertension (high blood pressure)
• Multiple sclerosis (MS)
• Cognitive impairment in the elderly
• Depression
• SAD (seasonal affective disorder)
• Obesity
• Osteoporosis
• Various bone disorders
• Parathyroid problems
• Heart disease