Ever Wondered Why We Need Vitamin D?

A small change for a healthier you, here’s how!

Updated: Friday 19 March 2021

vitamin d

What is Vitamin D, anyway?

The vitamin D in your body is actually classed as a hormone. This is because your body converts the vitamin D it receives from food, supplements or from sunlight into a hormone called calcitriol (basically, activated vitamin D, or D3).

Vitamin D is fat-soluble vitamin that supports the intestinal absorption of calcium, magnesium, phosphate, iron, and zinc.

Do I really need it?

Yes, yes you do. It is an essential vitamin, which means that your body needs it to function properly. Your body can make about 90% of the amount you need from sunlight and the other 10% from foods containing higher amounts of the vitamin.

Studies have proven that Vitamin D has an effect on diseases other than rickets, such as Alzheimer's, depression, multiple sclerosis.

And why in Winter?

No sun means weak UV light. There goes about 90% of your vitamin D source so to make up for it, taking vitamin D supplements is a good idea.

What does my body do with it?

We need this vitamin for the absorption of calcium and phosphate in our bodies. These minerals are used to maintain the strength of our bones, teeth and muscles. Also, it helps to regulate the immune system and evidence shows that it can even lower your risk of infections such as colds, flu and chest infections.

Why is the Vitamin D in my food not enough?

Foods such as liver, eggs, and oily fish contain higher levels of Vitamin D, but often these amounts are minimal and need to be taken in conjunction with other sources.

According to healthcare professionals at the National Institutes of Health, 1 serving of Vitamin D-rich food contains (in International Units or IU/day):

  • Cod liver oil - 1 tbsp 1360
  • Swordfish (cooked) 3 ounces - 566
  • Salmon (cooked) 3 ounces - 477
  • Tuna (canned and drained of water) 3 ounces - 154
  • Vitamin D-fortified orange juice (1 cup) - 137
  • Vitamin D-fortified milk (1 cup) - 115-124
  • Fortified yoghurt, 6 ounces - 80
  • Fortified margarine, 1 tbsp - 60
  • Canned sardines drained of water, 2 pieces - 46
  • Liver, beef, cooked, 3 ounces - 42
  • Yolk from 1 large egg - 41
  • Fortified cereal, 1 cup - 40
  • Swiss cheese 1 ounce - 6

Be sure to check the labels of the packets and cans of food you buy for their Vitamin D content.

What happens when you are deficient of this vitamin?

You are more susceptible to disorders such as rickets and osteomalacia, where your bones are weak and brittle so they are more easily broken and fractured.

So how much do you need per day?

In 2010, the Institute of Medicine recommends: for those between the ages of 9 and 70 years of age, the recommended dietary amount of Vitamin D per day is 600 Upper Level Intake (IU/day): 4000.

What goes wrong if you do not have enough Vitamin D?

In children - rickets

In adults - osteomalacia

The bones get soft and brittle, and you may experience pains in both your bones and muscles.

Can there be other reasons why you are low in Vitamin D?

There are certain diseases that can cause a deficiency in Vitamin D. With kidneys and liver diseases, this reduces the formation of enzymes needed to change the essential vitamin to a form that the body can use.

Other possible reasons your body is not breaking it down correctly can be because of cystic fibrosis, Crohn’s disease, celiac disease, gastric bypass surgery and obesity.

There are other factors, of course:

  • Age - as we age, the skin’s process of manufacturing vitamin D becomes much less efficient so the elderly have more chance of being deficient.
  • Mobility - if you do not get out much due to decreased mobility, there is not much chance of soaking up UV light from the sun.
  • Skin colour - fairer skin tends to produce more vitamin D than darker skin tones so the latter are more likely to be deficient in vitamin D.
  • Medications - certain drugs can also lower your levels of vitamin D - laxatives, steroids, drugs that lower your cholesterol, those that control seizures, rifampin for tuberculosis and weight loss drug orlistat.
  • Contact with the sun would include direct sunlight when the sun is at its highest point of the day in summer, such as during midday.

It is rare to receive this kind of exposure in the UK outside of the summer months May to August so it is important to maintain the levels of vitamin D in alternative ways such as through food.

Can I have too much Vitamin D?

Yes, it is best to stick to the recommended amount per day. An excess of this vitamin can see you with nausea, vomiting, confusion, reduced appetite, weakness, weight loss, kidney damage, itching, increased thirst and urination, constipation, and abnormal heart rhythms.

Bottom line?

Eat some foods rich in Vitamin D, take supplements and when the sun comes out, take it in for a while, like 10 minutes. Or 20 if you are in the UK.

Iris Barbier

Written by: Iris Barbier

Pharmacy Assistant

Born in France, Iris moved to the UK to study Biological Sciences at London Metropolitan University. Upon graduating, Iris moved up north, where she completed an MA in Science Journalism at the University of Lincoln.

As a qualified science journalist, Iris uses her expertise to write content for Pharmica’s online Health Centre. She ensures our patients get specialist knowledge on medical conditions and how to treat them.

Find out more about how we ensure the accuracy of our content with our content guidelines.

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