Vitamin D is one of the most vital vitamins our bodies need to maintain overall health. Medical experts reiterate at every opportunity that vitamin D affects so many mechanisms in our body and hence should be checked regularly to see whether we have sufficient levels or not. In fact, vitamin D deficiency can pave the way for major health problems such as rickets, heart disease and diabetes, leading to illness at any age. However, there is a group in particular that needs vitamin D even more than others: pregnant women. While a deficiency of vitamin D negatively affects the overall pregnancy and birth process of moms-to-be, it can also trigger many problems, from gestational diabetes specific to this period to even preterm labor.

Here's what gynecologist and obstetrician Dr. Oktay Kaymak from Istanbul's Acıbadem Altunizade Hospital has to say on the matter.

Diet alone is not enough

In a broad sense, vitamins are molecules that cannot be synthesized in our body and have to be taken from outside sources, which help the production and function of important enzymes and hormones. However, here is where vitamin D differs from other types of vitamins as it is the only vitamin that can be synthesized in the human body.

"The source of vitamin D is the foods we consume. Eggs, dairy products, fish and vitamin D-enriched foods are strong sources of it. Our kidneys and liver play a crucial role in making the vitamin D we consume via these nutrients widely available in the body," Kaymak said.

And that is why it is called the sunshine vitamin

"However, the foods we eat actually provide us with very little vitamin D. We need another source for sufficient vitamin D: the sun. No matter how much vitamin D-rich foods one consumes, they do not turn into a form the body can use to meet its needs adequately. For this transformation to happen, the skin needs to be exposed to the sun's rays. Vitamin D is synthesized under the skin and then becomes ready for the body to use," he said.

The way this conversion happens is that the sun's energy, specifically its ultraviolet B (UVB) rays, turns a chemical in our skin into vitamin D3, which is then transported to the liver and subsequently the kidneys, picking up along the way the oxygen and hydrogen molecules it needs to be converted into the biologically active form of vitamin D our bodies can actually use – calcitriol (also known as 1,25-dihydroxycholecalciferol).

"That is why for vitamin D, which is also of great importance for the development of the unborn baby, moms-to-be should get some sun often," he added.

Not every body part needs to see the sun

Short-term exposure of the face and hands to the sun's rays – roughly 15-30 minutes a day – is sufficient to meet our daily requirement of vitamin D. So whole-body sunbathing sessions for hours under the glaring sun will do more harm than good, especially without sunscreen.

Kaymak noted that vitamin D is crucial for many bodily functions, including but not limited to, bone metabolism, calcium levels, phosphorus balance, parathyroid and pancreatic hormone synthesis and balance, immunity and sexual function.

"In its deficiency, an increase can be observed in diseases such as rickets, osteomalacia (softening of the bone), decreased muscle functions, immune problems, cardiovascular diseases, diabetes, colon and breast cancer, as well as neuropsychiatric diseases such as depression, psychosis and Alzheimer's," he added.

Warning signals in pregnancy

Reiterating that vitamin D has many benefits for our body and is even more important for pregnant women, Kaymak said: "Vitamin D deficiency during pregnancy can lead to problems such as high blood pressure, latent diabetes, preterm labor and low birthweight. For this reason, vitamin D levels should be measured during pregnancy and adequate support should be given if there is a deficiency."

However, like everything in life, going overboard rarely yields positive results. Kaymak warned that taking excessive supplements of vitamin D will not provide additional benefits and can even backfire, causing problems such as kidney stones, hypertension, arrhythmia and even heart attack, in rare cases.

Hospitals in Turkey generally start pregnant women on 1,200 international units (IU)/day of vitamin D, about nine drops, during the whole course of the pregnancy, but these figures may change according to each individual. The obstetrician stressed that such supplements should also be taken under medical supervision.

Tips for pregnant women

"Get some exposure to sunlight every day, 20-30 minutes around noon. The best way to do this is to walk outside in the day, getting plenty of fresh air. This is a win-win because the mother-to-be gets some physical activity as well," he said.

"Pregnant women must also include foods rich in vitamin D in their diet and get bloodwork done regularly to monitor vitamin D levels and take supplements in case of deficiency," Kaymak said.