Vitamin D is widely known as the sunshine or bone vitamin. Recommendations and pseudo-truths about this nutrient frequently circulate, but what is actually true? It is, in fact, one of the vitamins whose deficiency is widespread globally. This blog post explains what vitamin D is responsible for in the body, who is at risk for deficiency, and how well it can be absorbed through sun exposure, diet, and supplements.

What is vitamin D?

Vitamin D is the umbrella term for the group of fat-soluble vitamins (calciferols). These are particularly well absorbed in combination with fat. The two most important forms of vitamin D are vitamin D2 (ergocalciferol) and the more well-known vitamin D3 (cholecalciferol). Although referred to as a vitamin, it is technically a hormone. Vitamins primarily occur in plants and are typically ingested through diet. In contrast, our bodies can produce vitamin D when exposed to sufficient sunlight. It plays vital roles in bone stability and metabolism. Vitamin D can be synthesized and stored by the body with the help of sunlight.

The different forms of vitamin D

Vitamin D, as mentioned, is the umbrella term for several forms of vitamin D. These forms are known as vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Both types are important for nutrition, with vitamin D2 synthesized from plants and yeast precursors and usually found in high-dose supplements. Vitamin D3 is the most active form, produced in the skin when exposed to direct sunlight. This form is also present in foods like grain and dairy products, cod liver oil, fatty fish, egg yolk, and liver.

The roles of vitamin D in the body

The term bone vitamin hints at where vitamin D mainly functions in the body. It ensures calcium and phosphorus are absorbed in the intestines and incorporated into the bones to maintain bone health. A deficiency in vitamin D impedes this process, resulting in insufficient calcium and phosphate for bone stability.

Firstly, the ingested vitamin D2 and D3 must be converted into an active form, known as calcitriol, in the liver. The liver, fat, and muscle tissues also serve as storage for vitamin D3, which should be replenished in summer for the body to utilize in winter. The storage capacity is sufficient to allow the body to get through winter months with well-filled stores.

Calcitriol is essential for bone formation, growth, and repair. Strong teeth also require calcium and phosphate. Vitamin D is not only crucial for bone metabolism but also impacts muscle strength.

How does a vitamin D deficiency occur?

Inadequate vitamin D supply over time can lead to a deficiency. Those who spend little time in the sun and also consume little vitamin D through diet are at risk. Between October and March, the body does not receive enough vitamin D. Therefore, it is crucial to ensure adequate intake and replenish stores during summer. Without these stores, a deficiency is almost inevitable. In northern and southern latitudes, sufficient vitamin D intake is nearly impossible due to weak sunlight during these periods. Certain conditions, such as malabsorption, can hinder vitamin D production in the skin, requiring patients to monitor their vitamin D levels.

Who is at higher risk for vitamin D deficiency?

People today spend a lot of time indoors due to their jobs and indoor leisure activities. A vitamin D deficiency is thus widespread across all age groups, with some being at particular risk:

• Breastfed infants: Breast milk contains very little vitamin D. Infant formula is usually fortified with vitamin D to ensure adequate supply for newborns.

• Young children: Young children should not be exposed to direct sunlight due to their sensitive skin.

• Pregnant women: Pregnant women can pass their vitamin D deficiency to the fetus, increasing the risk of rickets in the child.

• Elderly people: As people age, their need for vitamin D increases, and their ability to produce it decreases. Older adults also tend to spend more time indoors and may have mobility limitations.

• People who cover up for religious or cultural reasons: Those who keep their bodies covered even in summer are at risk.

• People taking medications like antiepileptics or cytostatics: These medications can interfere with the conversion of inactive to active vitamin D.

• People with chronic liver, kidney, or hereditary diseases: These conditions can also impair vitamin D metabolism.

   

For those with existing health conditions, it's important to discuss vitamin D intake or supplementation with their doctor.

Symptoms of vitamin D deficiency

Vitamin D is crucial for bone health, so a deficiency often manifests as bone or muscle pain in adults. It can lead to osteomalacia, a condition where bones become brittle due to decalcification. In older adults, this bone weakness can cause fractures from minor falls, affecting the spine, pelvis, or legs.

In infants and young children, a deficiency can cause more severe rickets: insufficient mineralization can slow skull closure or lead to bone deformities or a curved spine. Delayed crawling and sitting can occur. Children and adolescents with vitamin D deficiency often experience pain while walking, and severe deficiency can cause knock-knees or bowlegs.

Vitamin D also plays a significant role in the immune system. Insufficient vitamin D can increase susceptibility to infections, with recurring colds, coughs, or runny noses indicating a possible deficiency.

Diagnosing vitamin D deficiency

Vitamin D levels should be measured with a blood test during annual check-ups. If symptoms like bone or muscle pain appear, a medical check-up is necessary. In some cases, doctors may order X-rays to detect bone changes before symptoms appear. If low vitamin D levels are detected, calcium and phosphate levels should also be checked.

Preventing vitamin D deficiency

Regular sun exposure is the best way to prevent vitamin D deficiency. The general recommendation is to expose the face, arms, and hands to direct sunlight at least three times a week for 5 to 15 minutes. Darker skin or older age may require longer exposure.

Always ensure sun exposure is within your skin's natural protection time to avoid sunburn, skin diseases, and skin damage. Sunscreen inhibits vitamin D production because it blocks not only UVA rays but also UVB rays necessary for vitamin D synthesis. Therefore, the safest option to maintain sufficient vitamin D levels is supplementation with appropriate products. Those unable to achieve the desired concentration through sunlight or who spend a lot of time indoors should consider supplements in the form of drops. This ensures good vitamin D levels throughout summer and a sufficient winter reserve.

Vitamin D from food

There is a persistent belief that vegans are more prone to vitamin D deficiency because it mainly occurs in animal products. However, vitamin D levels in most foods are negligible, as only about 10 to 20% of the required amount comes from diet. The body produces the majority when exposed to direct sunlight.

Tanning beds as an alternative?

Many people use tanning beds in winter for a year-round tan and as an alternative vitamin D source. Dermatologists advise against this method due to the high risk of skin cancer. The UVB radiation in tanning beds is as intense as the midday sun in the Mediterranean during summer. For vitamin D deficiency, high-quality supplements in drop form are recommended instead of tanning beds. Some doctors also offer vitamin D injections directly into the bloodstream.

600 IU vs. 2,500 IU – who needs how much?

Researching vitamin D supplements, you'll encounter the term IU. IU stands for International Units, measuring the function or activity of a substance. The World Health Organization has established these values, with the conversion for vitamin D as follows:

• 1 IU equals 0.025 μg

• 1 μg equals 40 IU

The estimated requirement for someone over one year old is a daily dose of 20 μg (800 IU). On a sunny day, human skin can produce about 10,000 IU. In comparison, foods provide only a negligible amount of vitamin D:

• 2 liters of whole milk: about 80 IU

• 100 g of herring with 15 g of fat: 960 IU

• 100 g of smoked eel with 25 g of fat: 880 IU

• 2 medium eggs: about 116 IU

Fatty fish is the only dietary source that can somewhat meet the daily requirement. However, fish consumption is recommended 1 to 2 times a week, making it an unsuitable primary vitamin D source due to environmental concerns. product recommendations :