Vitamin D — Importance, Dosage and Benefits of the Sunshine Vitamin — Biohacker’s Base

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Vitamin D is actually a group of fat-soluble vitamins responsible for the intestinal absorption of calcium, magnesium, and phosphate. The most important from the group are vitamins D3 (also known as cholecalciferol) and D2 (ergocalciferol). It is essential for the normal absorption of calcium and phosphorus, which are needed for healthy bones. Recent studies showed that many other cells have vitamin D receptors, especially the immune system cells 1).


The vitamin D produced by the body when exposed to UVB (with a wavelength of 290–320 nanometers) or ingested through food or supplements is biologically inert. It has to go through two hydroxylations in the body in order to become active. The first one occurs in the liver and converts vitamin D to 25-hydroxyvitamin D, also known as calcidiol. The second one occurs in the kidney and produces 1,25-dihydroxyvitamin D, also known as calcitriol.

Sunshine Vitamin

Is also called the “sunshine vitamin” because our bodies are able to synthesize this when exposed to sunlight. In the presence of UV radiation (especially UVB), the skin produces Vitamin D3 (cholecalciferol) from a derivative of the steroid cholesterol. When we don’t expose ourselves enough to sunlight, we can develop vitamin D deficiency.

You can also get your Ds from food and supplements. When it comes to food, only small fish (sardines and herring) and fatty fish (like tuna, mackerel, and salmon) have significant amounts of it. You can also get some amounts from beef liver, cheese, and egg yolks or from fortified foods like milk, soy milk, orange juice, cereals.

Bottom line is that if you don’t get enough sun exposure, it is unlikely to get enough from your food, so you should also take some supplements. Cod liver oil is a popular supplement, containing about 448 IU per teaspoon. It is also rich in vitamin A and omega-3 fatty acids.

Vitamin D Deficiency

I will focus more on the effects of not having the needed amounts in your body, but this will also shed light on the benefits of vitamin D.

The most known effect of its deficiency is age-dependent:

  • in case of kids, it can cause rickets, a condition that results in weak bones, bowed legs, bone pain, large forehead trouble sleeping;
  • for adults, it leads to osteomalacia, causing bone pain and muscle weakness, and leads to easy fractures.

Signs of Deficiency

Most people don’t realize that they’re vitamin D deficient, because symptoms are generally subtle. Even though they have a significant negative effect on your quality of life, you might not easily recognize them.

Here are some of the most important signs of deficiency:

Causes of Deficiency

The main cause of its deficiency is lacking sun exposure, but it can be accentuated by using sunscreen, living in an area with high pollution or having a darker skin tone, being obese or being elderly. Your geographical position also has an important role: people who live at latitudes above 37 degrees north or below 37 degrees south of the equator don’t get enough UVB energy from the sun for proper vitamin synthesis.

How Much Do You Need?

Dosage can be expressed as micrograms per or international units (IU) per day. An international unit (IU) is an internationally accepted amount of a substance. This type of measure is used for the fat-soluble vitamins (such as vitamins A, D, and E) and certain hormones, enzymes, and biologicals (such as vaccines) . You can convert between IU and mcg using this formula: IU/40 = 1 mcg .

The current intake recommendations from the Dietary Reference Intakes are:

  • Children and teens: 600 IU/day
  • Adults, up to age 70: 600 IU/day
  • Adults, over age 70: 800 IU/day
  • Pregnant and breastfeeding women: 600 IU/day

Some authorities recommend 800 or even 1000 IUs a day. Beware though that this is a fat-soluble vitamin, so it’s stored in the body’s adipose tissue (fat). This is good as the body can use the reserves when your intake and production are low, but it can also become bad when excessive doses build up to toxic levels. At toxic levels, it can drive up calcium levels in the blood, causing grogginess, constipation, and even death. One needs massive overdosing in order to reach this state — doses up to 2,000 IU are considered safe. There is no determined threshold for toxicity — some indicate 4,000 IU, while others claim that overt toxicity appears after several months of 50,000 IU intake .


Both an excess and a deficiency in vitamin D appear to cause abnormal functioning and premature aging. You need to make sure you help your body maintain adequate levels of this vitamin and simple sun exposure is not as efficient as it used to be decades ago. Try to eat fish (especially sardines and herring), and take supplements.

Originally published at on January 22, 2020.

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