Like other vital nutrients, it is important to ensure you get enough vitamin D. Low levels can affect your health and wellbeing in significant ways. But before we discover how and why, we need to answer a more basic question. 


Just what is vitamin D and why do you need it?

We’ve all heard the name. Vitamin D is one of a small group of core nutrients, alongside such old friends as vitamin C, vitamin B and vitamin E. But the situation is more complex than it may appear. Vitamin D is, in fact, not one substance but a group of five. Vitamins D1 to D5 are all closely related fat-soluble natural steroids. Vitamins D2 and D3 are the most important for human health. Steroids are a type of biologically active organic compound.

Vitamin D is vital to health. It is used by the body to balance the levels of calcium and phosphate in our bloodstreams. These two minerals are fundamental building blocks of bone. Vitamin D is also involved in the regulation of cell growth, the modulation of nerves within muscles, and the metabolisation of glucose. According to multiple studies, it also plays a role in promoting the health of our immune systems, triggering the release of antibodies and thereby helping the body to fight off illnesses more easily.

Vitamin D is distinct from other vital nutrients in one key way: it is the only vitamin that our bodies can produce themselves. Vitamin D3, also known as cholecalciferol, is synthesised from cholesterol in our skin (specifically the outer layer, or epidermis) following exposure to sunlight.


The dangers of vitamin D deficiency

Vitamin D deficiencies are surprisingly common, especially in colder northern climates where sun exposure is lower.

Low levels of vitamin D can reduce calcium absorption from an average of around 70% (of a particular food source) to as little as 15%. This means bone softening is the primary risk of vitamin D deficiency.

The childhood bone disorder rickets is now rare in the developed world but adult illnesses like osteoporosis and osteomalacia have lingered on. The former involves impaired bone mineralisation, leading to more fragile bones and an increased risk of fracture. Meanwhile, osteomalacia combines bone thinning with the weakening of attached muscles. Women who have given birth to several children are at particular risk of osteomalacia.

Muscle weakness is another common symptom of vitamin D deficiency. Sufferers may experience pain or muscle tremors.

Low levels of vitamin D have also been linked to an increased risk of:

  • Dental problems – for example, periodontitis, an inflammatory bone disorder which can cause tooth loss
  • Cancer
  • High blood pressure
  • Autoimmune illnesses – for example, diabetes type 1, inflammatory bowel disease and psoriasis
  • Pre-eclampsia – a potentially serious pregnancy complication characterised by high blood pressure


How to maintain healthy vitamin D levels

Sunlight is the single biggest source of vitamin D for most people, and it’s important to distinguish between vitamin D & vitamin D3. Some foods contain vitamin D but they are relatively limited compared to other nutrients.

The major dietary sources of vitamin D are:

  • Fatty and oily fish – for example, herring, mackerel, salmon, sardines
  • Egg yolks
  • Red meat
  • Liver

And that’s pretty much it. Dietary supplements are also available of course, and some processed foods are fortified with vitamin D during manufacture – for example, breakfast cereals.

So what are the optimal d vitamin levels? According to a close examination of available data by the US Food and Nutrition Board, a blood serum level of 12 nanograms of vitamin D per millilitre (ng/mL) indicates a likely deficiency and the risk of deficiency remains up to 20 ng/ mL. For maximum health benefits, the Endocrine Society recommends a blood serum level of 30 ng/ mL.


How to measure your levels

So what do you do if you want to ensure your vitamin d levels are normal and healthy? The first and most important step is to measure yours. Are you getting enough or do you have a deficiency? Your GP may be able to refer you to a nutritionist for testing, but why wait months for an appointment? You can test your vitamin D levels at home.

Take a blood sample using a simple, painless finger prick, and you will soon receive a full analysis of your current vitamin D levels. If yours are low, you will be able to adjust your diet and levels of exposure accordingly.


Written by Bev Walton, BSc Nutritional Science

I achieved a First-Class Honours degree in BSc Nutritional Science, Nutrition Sciences from the University of Reading and now have over 35 years experience in all types of cuisine, dietary plans, recipe development, health and nutrition. I have been writing for over 10 years for magazines and websites as well as ghostwriting for ebooks, Kindle and fully published books. I’m also a proud member of the Guild of Food writers.

Bev Walton | University of Reading BSc Nutritional Science, Nutrition Sciences