The Best Vitamin D supplements: Shopping Guide and Recommendations (01/23)

Vitamin D is not a vitamin in the true sense of the word, but a hormone. Unlike other vitamins, vitamin D can be produced in the body with the help of UV-B radiation. In humans, vitamin D is largely produced in the skin under the influence of sunlight and is only absorbed to a small extent through food. Vitamin D is involved in the regulation of important metabolic processes and is responsible for the regulation of entire systems of the human organism.

Some studies see a positive influence of vitamin D supplements on muscle performance, others deny such an effect. A 2019 meta-study concluded that vitamin D supplementation positively affects muscle strength in the lower extremities, but not in the upper extremities (3).

Effect on the immune system

Vitamin D is also important for a functioning immune system. If there is a serious deficiency of the sun vitamin, the body’s own defences are weakened. Vitamin D helps produce defence cells and substances and prevents inflammatory immune reactions. In addition, it seems that people with high vitamin D levels get sick less often (4).

Scientists disagree about whether vitamin D can prevent cancer. What is certain is that vitamin D influences the immune system, which is important for the defence against cancer cells (5). In a review from 2014, a research team summarised all the previously published studies on this topic – a total of 18 studies with around 50,000 people (6). The results are sobering. The researchers believe it is possible that low vitamin D levels are not the cause of certain diseases such as cancer, but merely the consequence.

Older people often only rarely come into contact with the sun or the skin’s ability to produce vitamin D decreases. This can quickly lead to a vitamin D deficiency. People whose skin is more pigmented need more sunlight for their body’s vitamin D production than less pigmented people.

Light-skinned people also need to be careful: If you always use sunscreen outside, UVB radiation will not reach your skin. In this way, you largely prevent the production of vitamin D.

Risk groups also include people who suffer from chronic gastrointestinal, liver or kidney diseases or who take medicines that impair vitamin D metabolism (e.g. antiepileptic or cytostatic drugs). Likewise, pregnant and breastfeeding women, infants and small children have an increased vitamin D requirement. Night shift workers or people who do not show much naked skin due to their job or for cultural or religious reasons can also benefit from an additional vitamin D intake.

Some studies indicate that a good normal value must be at least 30 ng/ml. Moreover, a higher normal value or a value slightly above the normal range is said to have more positive effects than a value below 30 ng/ml (1, 8, 2).

The goal is therefore to maintain a level above 30 ng/ml in both children and adults in order to reap the full health benefits of vitamin D. The German Nutrition Society (DGE) speaks of a desired vitamin D supply in terms of bone health at a blood concentration of at least 20ng/ml. If the body’s own vitamin D formation is lacking, this concentration is achieved with an intake of 20 micrograms of vitamin D per day.

The concentration of 25-hydroxyvitamin D in blood serum is used as a marker for assessing supply because it reflects vitamin D intake through diet and the body’s own vitamin D production. Vitamin D values can be expressed in two different units, ng/ml or nmol/l. 1 ng/ml corresponds to 2.5 nmol/l. At a normal value, there are usually no health consequences to worry about. These only become apparent in the case of an undersupply or, at the latest, a severe vitamin D deficiency below 20 ng/ml.

The only way to find out your vitamin D level is to take a blood test. If you tell your doctor about symptoms that occur with a vitamin D deficiency, he or she will carry out a blood test. However, vitamin D blood tests are usually not necessary. What you get in vitamin D in spring, summer and autumn will usually supply your body in winter as well. Vitamin D is stored in the body for several months.

Your body can benefit from vitamin supplementation in many ways. However, you should not overdo it with the dosage. But there is no need to worry too much, because hypercalcaemia is only observed at a daily vitamin D dosage of about 40,000 IU. Even at very high doses of around 10,000 IU daily, however, no symptoms of hypercalcaemia could be found (9, 10).

Each form has its advantages and disadvantages. Whether you choose vitamin D in tablets or capsules or in liquid form as drops depends solely on your preferences and needs. The following is a brief overview of the different forms of vitamin D.

Vitamin D drops

Vitamin D drops can be dosed individually and are easier to swallow than capsules or tablets. They also contain little or no additives. Therefore, drops are the ideal form of administration for babies and small children to cover their vitamin D needs.

With drops, the vitamin is already in an oily solution, which allows your body to absorb and utilise the vitamin D optimally. Studies have shown that liquid vitamin D (dissolved in oil) increases vitamin D levels more quickly than other forms of administration (12, 13).

Since vitamin D drops often do not contain preservatives, they do not have as long a shelf life as capsules or tablets. When buying vitamin D, check the best-before date and choose the best package size for you. In addition to the short shelf life, the higher price is one of the disadvantages of vitamin D drops.

Vitamin D tablets

Tablets are one of the most popular forms of vitamin D. They are usually very cheap. They are usually very inexpensive and have a long shelf life. Tablets are also a very popular form of administration because of their low price.

Additives are added to vitamin D tablets during production. Although these are considered harmless, they reduce the purity of the preparation. In addition, vitamin D tablets should be taken with meals together with some fat in order to be better absorbed by the body. In one study, the increase in vitamin D levels was lowest when taking vitamin D tablets (12).

Vitamin D capsules

Vitamin D3 soft capsules or softgels are rubbery capsules filled with vitamin D3 already dissolved in liquid. This form of preparation contains virtually no additives and is therefore purer than vitamin D tablets. In addition, the vitamin D absorption from capsules is better than from tablets (12).

As a disadvantage, it should be mentioned that the capsule shells are often made of gelatine and are therefore not suitable for vegetarians and vegans. Capsules are also more expensive to produce than tablets. Unlike drops, however, capsules do not contain vitamin D dissolved in oil. An exception are the so-called soft capsules, which are tightly closed capsules containing vitamin D oil or gel.

As a rule, you have to pay for vitamin D supplements yourself. Only if there is an actual deficiency and your doctor prescribes the preparation will the health insurance fund cover the costs. The recommendations of the German Nutrition Society (DGE) are often used as a basis for vitamin D deficiencies, which many critics say is far too low.

You should also make sure you have a sufficient supply of magnesium. Your body needs this mineral to convert vitamin D into its active form. If there is not enough magnesium in your body, vitamin D supplementation is of no use. The vitamin remains unused because the transport molecules do not work without magnesium.

Caution: Calcium should only be supplemented by people at risk of osteoporosis to reduce the risk of bone fractures. In healthy people, an oversupply can damage the body.