How much vitamin D does it take to strengthen your defences against depression, cancer and COVID?

Fewer sick days, better mood and energy levels at work and at home, and a stronger immune system are three benefits of the right amount of vitamin D.

How do you know how much vitamin D you need? Without a clear answer, it may be nigh-on impossible to match your situation to health authorities’ recommendations for vitamin D.

Many people are, without knowing it, lacking Vitamin D. A 2021 survey estimates the number to be around one billion people around the world.

Without enough vitamin D, there can be increased risks to your physical and mental health, like developing depression or a long list of physical illnesses, including some cancers. Research also suggests that vitamin D may have some positive effects related to COVID. However, too much vitamin D can be dangerous to your health.

Therefore, it makes excellent sense to conduct regular tests that can provide clear, proactive insights into your vitamin D levels.

What is vitamin D?

Vitamin D is a fat-soluble vitamin that, among other things, promotes the absorption of calcium, regulates bone growth, and plays a major role in various immune functions.

Vitamin D comes in two different forms: D2 and D3.

The human body transforms both types to the active form, 1,25-dihydroxycholecalciferol. Some studies indicate that Vitamin-D3 is more efficient for the conversion process.

What are the consequences of too little or too much vitamin D?

If you have too little vitamin D, you run several risks for your mental and physical health.

A study covering 31,424 participants by McMaster University shows that low vitamin D levels increase the risk of suffering from depression. Furthermore, it increases risk of schizophrenia and seasonal affective disorder.

Low levels of D-vitamin have also been associated with increased risk of osteoporosis, heart disease, diabetes, and certain cancers, such as colorectal cancer. Furthermore, adequate amounts of vitamin D seem to lower the risk of developing breast cancer.

If you have too high vitamin D levels (often caused by taking excess supplements), it may lead to nausea and vomiting and can develop into bone pain and kidney problems, such as kidney stones.

How do I know if I am getting the right amount of vitamin D?

Signs of incorrect amounts of vitamin D can be difficult to spot. Some people have no symptoms, while others experience soreness and pain or feel unusually tired.

The most accurate way to measure how much vitamin D you have in your body is a blood test. The result can show if you have too low, adequate, or too high vitamin D levels.

Between 20 nanograms/millilitre (ng/ml) and 50 ng/ml are considered appropriate for healthy people. A level of less than 12 ng/ml indicates vitamin D deficiency.

The EU’s Scientific Committee on Food has set the safe upper limit for microgram (µg ) daily intake of vitamin D to:

  • 25 µg for infants from 0 – 6 months
  • 50 µg for children from 6 months – 10 years and
  • 100 µg for children from 11 and up and adults, incl. breastfeeding mothers

Should I take supplements to get enough vitamin D?

In general, the answer is yes, but without testing, it can be very difficult to give a clear answer.

Various healthcare organisations will have different recommendations but generally recommend supplements. For example, the Danish health authority, Sundhedsstyrelsen, recommends that individuals aged four and up take a daily supplement of 5-10 µg of vitamin D during the winter months (October to April). Children under the age of four are recommended 10 µg of vitamin D all year round.

10 µg daily are recommended for vulnerable sections of the population, including people who do not get enough sunlight. In addition, they recommend 20 µg for the elderly over 70.

Vitamin D and COVID

The possible links between vitamin D and COVID is a hotly debated topic. However, some research results suggest that too little vitamin D may influence how the body responds to being infected respiratory diseases, such as the novel Coronavirus:

  • In a study published in Nature in 2020, a group of researchers pointed out that COVID-infected people with low levels of vitamin D were at greater risk of serious complications.
  • An Australian study from 2017 shows that vitamin D has a preventive effect on respiratory diseases.
  • An analysis of individuals in Chicago suffering from COVID showed a 2,5x increased risk of becoming infected if one has low vitamin D levels.

In this context, it should be noted that for all results, follow-up, in-depth research is needed before anything can be said with total clarity about any possible causal relationships between Vitamin-D and COVID-19.


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The information is not intended as a substitute for professional medical advice, diagnosis, or treatment. Seek advice from a physician or other qualified healthcare professional with any questions you may have regarding a medical condition or treatment and before beginning a new healthcare treatment. Do not ignore or delay professional medical advice due to information you have read on this website.

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