Vitamin D Intake: Pregnancy Safety

Vitamin D is an essential nutrient during pregnancy, supporting the healthy development of the baby and the mother's wellbeing. The recommended daily intake of vitamin D during pregnancy ranges from 400 to 600 IU, according to various health organisations. However, recent studies suggest that higher doses of up to 4000 IU per day are safe and may provide greater benefits in preventing preterm births and infections. Vitamin D supplementation during pregnancy is particularly important for those at increased risk of deficiency, including vegetarians, individuals with limited sun exposure, and ethnic minorities with darker skin.

Sources of vitamin D

Vitamin D is a fat-soluble vitamin that is both a nutrient we eat and a hormone our bodies make. It is essential for the absorption and metabolism of calcium and phosphorus, and plays a critical role in maintaining bone strength and skeletal integrity. While our bodies produce vitamin D when exposed to sunlight, it can also be obtained through certain foods and supplements. Here are some sources of vitamin D:

• Sun Exposure: Vitamin D production in the skin is the primary natural source of vitamin D. However, people living in places with limited sunlight or those who spend most of their time indoors may have insufficient levels. Additionally, people with darker skin tend to have lower vitamin D levels as melanin acts as a natural sunscreen, reducing its production.
• Fatty Fish: Salmon, herring, sardines, halibut, mackerel, and cod liver oil are excellent sources of vitamin D. Wild-caught salmon typically contains higher levels of vitamin D compared to farmed salmon.
• Egg Yolks: Eggs, especially those from chickens raised outdoors or fed vitamin D-enriched feed, are a good source of vitamin D.
• Fortified Foods: Many foods are fortified with vitamin D, including cow's milk, plant-based milk substitutes (such as soy milk), orange juice, cereals, and oatmeal. However, it is important to check the labels as the vitamin D content can vary widely.
• Mushrooms: Wild mushrooms or commercially grown mushrooms exposed to UV light contain vitamin D2.
• Supplements: Vitamin D supplements are available in two forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The recommended daily intake of vitamin D ranges from 400 to 2000 IU, but higher doses of up to 4000 IU per day are considered safe for adults.

Recommended daily intake

The recommended daily intake of vitamin D during pregnancy varies according to different organisations' guidelines. The Institute of Medicine recommends 600 international units per day, while the National Institute for Health and Clinical Excellence in the United Kingdom suggests 400 international units. The Endocrine Society and the Canadian Society recommend a higher intake of 1500–2000 and 2000 international units, respectively.

Results from recent randomised controlled trials on vitamin D supplementation in pregnancy suggest that a safe dose is between 2000 and 4000 international units per day. The daily upper safe limit has been set at 4000 international units by the Institute of Medicine and 10,000 international units by the Endocrine Society.

For pregnant women at increased risk of vitamin D deficiency, most experts agree that 1000–2000 international units per day is safe. However, higher-dose regimens used for treating vitamin D deficiency have not been studied during pregnancy.

It is recommended that pregnant women who do not take a vitamin D supplement do so, as there is a risk of their child developing soft bones and rickets, a disease affecting bone development.

Benefits of vitamin D during pregnancy

Vitamin D is a steroid vitamin and a fat-soluble prohormone. It is beneficial for both the health of the mother and the development of the baby.

Benefits for the mother

Vitamin D has been found to play a role in immune function, healthy cell division, and bone health. It is also necessary for the absorption and metabolism of calcium and phosphorus. Studies have found a link between low vitamin D levels and an increased risk of certain types of cancers, autoimmune disease, neurological disease, insulin resistance, and cardiovascular disease.

Benefits for the baby

Vitamin D supports healthy bone development in the baby. A deficiency in vitamin D for the mother has been linked to preeclampsia and preterm birth.

Who is at risk of vitamin D deficiency?

40-60% of the US population is vitamin D deficient, including pregnant women. This is partly because there are very few vitamin D-rich foods: egg yolk, salmon, and cod liver oil. For the 75% of the population that is lactose intolerant, milk is not a reliable source of vitamin D. Other factors that influence vitamin D deficiency include:

• Where you live
• The season
• How much time you spend outdoors without sunscreen
• Skin pigmentation
• Age
• Obesity
• Pollution
• Having unhealthy intestines with suboptimal absorption capacity

All pregnant women should take a 10 microgram (or 400 IU) supplement of vitamin D each day. Do not take more than 100 micrograms (4,000 IU) of vitamin D a day as it could be harmful.

Risks of vitamin D deficiency during pregnancy

Vitamin D deficiency is common during pregnancy, and it can have severe consequences for both mother and child. The risks of vitamin D deficiency during pregnancy include:

• Biochemical evidence of disordered skeletal homeostasis: During pregnancy, severe vitamin D deficiency has been linked to disordered skeletal homeostasis, which can lead to bone problems for both mother and child.
• Congenital rickets and fractures in newborns: Vitamin D is necessary for the absorption and metabolism of calcium and phosphorus, which are essential for bone development. Deficiency can lead to congenital rickets and fractures in newborns.
• Low birth weight: Some studies suggest a correlation between vitamin D deficiency and low birth weight, but more research is needed to confirm this.
• Preeclampsia: Vitamin D plays a role in preventing preeclampsia, and deficiency has been associated with an increased risk.
• Gestational diabetes: There is some evidence that vitamin D deficiency may be linked to gestational diabetes, but further research is needed.
• Preterm birth: Vitamin D may play a role in preventing preterm birth, but the evidence is inconclusive.
• Maternal health issues: Vitamin D deficiency can cause muscle aches, weakness, bone pain, and softened bones, which may lead to fractures. It has also been linked to an increased risk of autoimmune diseases, cardiovascular disease, and certain types of cancer.
• Infant health issues: Infants born to mothers with vitamin D deficiency are at risk of vitamin D deficiency themselves, which can lead to rickets (weak, soft bones) and other health issues.

Signs of vitamin D deficiency

During pregnancy, severe vitamin D deficiency has been associated with congenital rickets and fractures in the newborn. Maternal vitamin D levels have also been linked to adverse outcomes such as preeclampsia, pregnancy-induced hypertension, high blood pressure in diabetic pregnancy, gestational diabetes mellitus, recurrent pregnancy loss, preterm delivery, primary Caesarian section, and postpartum depression.

Vitamin D is a fat-soluble vitamin that is essential for health. It is produced in the skin through exposure to sunlight and can also be obtained from certain foods or supplements. Vitamin D plays a critical role in the proper functioning of the body, including bone health, immunity, and calcium absorption.

• Bone pain or achiness: Low vitamin D levels can lead to inadequate calcium absorption, resulting in bone pain, fractures, and an increased risk of falls, especially in older adults.
• Muscle weakness or pain: Vitamin D deficiency can cause muscle weakness, especially in body parts near the trunk, such as the upper arms or thighs. It has also been associated with chronic pain and conditions like arthritis.
• Fatigue and tiredness: Research suggests that vitamin D deficiency may contribute to fatigue and poor sleep quality.
• Mood changes and depression: Vitamin D deficiency has been linked to depression, especially in older adults, and may also be associated with anxiety.
• Frequent illness: Vitamin D plays a role in immune function, and low levels can increase the risk of respiratory tract infections, viral diseases, and other illnesses.
• Impaired wound healing: Vitamin D is important for controlling inflammation and addressing infections, which are crucial for proper wound healing.
• Hair loss: Studies have linked low vitamin D levels to alopecia areata, an autoimmune disease characterized by severe hair loss.

It is important to note that many people with vitamin D deficiency may not exhibit any symptoms, and doctors do not routinely check vitamin D levels. However, if you are experiencing any of the above symptoms or are at risk of vitamin D deficiency, it is recommended to consult a healthcare professional for further evaluation and appropriate treatment.

Frequently asked questions