All About Vitamin D: The Definitive Guide to the Sunshine Vitamin

Vitamin D

Vitamin D is a nutrient necessary for health. It’s especially important for maintaining strong bones by helping the body absorb the calcium you get from food and supplements.

Getting too little vitamin D can actually put you at risk of developing thin, fragile bones, a condition known as Rickets in children and osteomalacia in adults.

But that’s not where the benefits of vitamin D end. Our muscles need it to function properly; it also plays a critical role in transmitting information between nerves. Our immune system needs vitamin D to fight viruses and bacteria.

Vitamin D is a little different from other vitamins. Despite its name, vit D is actually a hormone produced through sunlight exposure. That’s why it’s often referred to as ‘the sunshine vitamin’.

What Is Vitamin D?

It’s a fat-soluble vitamin, which means it is dissolved in fats and oils. It also means that it gets stored for longer in your body.

There are 2 forms of vitamin D:

  • Vitamin D3 (cholecalciferol): Also known as cholecalciferol, vitamin D3 is also found in a limited number of animal sources.
  • Vitamin D2 (ergocalciferol): Also known as ergocalciferol, vitamin D2 is also found in some plants, mushrooms and yeasts.

Of the 2 vit D forms, vitamin D3 (cholecalciferol) is twice as effective at increasing vitamin D levels compared to vitamin D2 (ergocalciferol).

Vitamin D Sources

vitamin D sources
Healthy foods containing vitamin D

If you’re looking for sources of vitamin D, we’ve got you covered. Here’s a list with the best vit D sources, from sunshine to mushrooms:

  • Sunshine: Your skin produces vitamin D when exposed to ultraviolet B rays (UVB). The more time you spend in the sun, the healthier your vitamin D levels will be. However, make sure you wear sunscreen to avoid sunburn and associated health issues.
  • Certain mushrooms: Mushrooms have the unique ability to produce vitamin D when exposed to UV light.
  • Egg yolks: Free range and organic eggs are important sources of vitamin D.
  • Cheese: Cheese is a natural source of vitamin D, albeit it only contains minimal amounts of this nutrient.
  • Fortified foods, including yoghurt, margarine and certain brands of oatmeal
  • Supplements: A wide range of vitamin D supplements are available. Most D3 supplements are derived from lanolin, which is a compound found in sheep wool. If you’re looking for vegan vitamin D3, then a supplement derived from lichen might be an ideal option for you. On the other hand, supplements containing vitamin D2 are typically derived from the yeast of mushrooms that have been exposed to UV rays.
  • Fatty fish: Tuna and salmon are excellent sources of Vitamin D.
  • Pork: It is preferable to opt for lean meat because this is where the highest concentration of nutrients is found.

Vitamin D Health Benefits

  • Reduced risk of osteoporosis and bone fractures
  • Cancer prevention: One study noted that 1,100 IU / day alongside calcium may reduce cancer risk by 60%.
  • Low mood support
  • Reduced risk of type1 diabetes.
  • Contributes to the normal function of the thyroid, parathyroid and pituitary gland
  • Enhances the function of vitamins A and C in the body
  • Contributes to the prevention of autoimmune diseases 

Vitamin D Deficiency

Vitamin D deficiency is especially common in people with the following conditions:

  • Cystic fibrosis 
  • Crohn’s disease
  • Coeliac disease

These conditions don’t allow the intestines to absorb and/or synthesise enough vitamin D.

Over 25% of the UK population is vitamin D deficient, according to the National Institute for Health and Care Excellence (NICE). Causes of vitamin D deficiency include:

  • Insufficient sunlight exposure (as our body produces vitamin D when sunlight hits the skin)
  • Not consuming foods that contain vitamin D
  • In cases of an extreme vegetarian diet, as most sources come from foods of animal origin.
  • Living in areas with little sunlight during the day, wearing long clothes or having an occupation that limits sun exposure.
  • Dark skin: Pigmented skin leads to a reduced ability of the body to produce Vitamin D
  • Kidney problems: As you age, your kidneys gradually lose their ability to convert vitamin D into its active form.
  • Obesity: Vitamin D is extracted from the blood by fat cells altering the release into the circulation. That’s why people with a body mass index (BMI) of 30 or more often are more prone to vitamin D deficiency.

If you’re worried you’re vitamin D deficient, the most common symptoms to look out for include:

  • Back pain
  • Muscle weakness
  • Fatigue
  • Vomiting
  • Hair loss

Treatment for vitamin D deficiency involves getting a higher intake of vitamin D through high-strength vitamin D supplements.

If you do not spend too much time in the sun or always take care to cover your skin or wear sunscreen (which is good for you, by the way), you should speak to your GP about taking vitamin D supplements.

How Much Vitamin D Should You Take

Knowing that you have a vitamin D deficiency is with a blood test. Anything under 12ng/ml is considered deficient. A result of 20ng/mg and above is adequate.

The recommended daily intakes of vitamin D are as follows:

  • Infants: 400 IU (10 mcg) / day
  • Children and adults: 600 IU (15 mcg) / day
  • Elderly people and pregnant / breastfeeding women: 800 IU (20 mcg)

Vitamin D Overdose

Toxicity from vitamin D is rare and happens only if you take extremely high doses for a long period of time. For adults (including pregnant and breastfeeding women, children aged 11-17 years and the elderly), the NHS warns against taking more than 4,000 IU (100 mcg) of vitamin D daily.

vitamin D supplements

Children between the ages of 1 and 10 years shouldn’t take more than 2,000 IU (50 mcg) a day. Infants under 12 months shouldn’t be given more than 1,000 IU (25 mcg) a day.

Excessive exposure to sunlight won’t cause vitamin D overdose. However it’s best to cover up or protect your skin using sunscreen if you’re out in the sun for long periods to help reduce the risk of sunburn, skin damage and skin cancer.

Symptoms of vitamin D toxicity include: 

  • confusion
  • drowsiness
  • depression
  • constipation
  • drowsiness
  • high blood pressure

Some categories of people should completely avoid vitamin D supplements. This includes people with specific medical conditions such as:

  • Sarcoidosis
  • Crohn’s disease
  • Metastatic bone cancer
  • William syndrome.

In general, moderate sun exposure (5-10 minutes / day or at least 3 times a week), as well as a balanced diet, are enough to maintain healthy levels of vitamin D.

Please note that the NHS recommends taking a vitamin D supplement containing at least 400 IU (25mcg) of vitamin D throughout the year.