Vitamin D, levels and deficiency
Vitamin D, levels and deficiency
Vitamin D is a fat-soluble vitamin which is found in foods such as oily fish, red meat, liver and egg yolks. Some foods, such as bread and spreads, are also fortified with vitamin D. However, unlike other vitamins where sufficient intake can be achieved through a healthy diet, the main source of vitamin D is sunlight.1
When skin is exposed to UVB rays, 7-dehydrocholesterol (a substance found in the skin) is converted in the liver and kidneys to an active form of vitamin D3 that can be used by the body.2
Vitamin D contributes to normal absorption and utilisation of calcium and phosphorus in the body. This is important for the formation and maintenance of healthy teeth and bones. Vitamin D also has a role in maintaining the normal function of muscles and the immune system.3
Some research suggests that vitamin D also has a role in a number of other conditions, such as depression, cancer, multiple sclerosis and diabetes, but there is currently insufficient evidence for this.4
There are two main types of vitamin D: vitamin D2 (ergocalciferol), which is produced by plants, such as mushrooms, and vitamin D3 (cholecalciferol), which is produced by animals. When advising on which supplement a customer should choose it is important to understand whether they are vegetarian or vegan. Vitamin D2 is always suitable for vegans, but vitamin D3 can be derived from an animal source (such as sheep’s wool) or lichen (a vegan-friendly source).
Vitamin D levels
It is estimated that one in five people in the UK have low vitamin D levels and are therefore at risk of various bone and muscle disorders.4 In 2016, guidance was issued by the NHS on vitamin D supplementation. The pharmacy team have a role to play in ensuring customers are aware of the guidelines and the importance of maintaining their vitamin D levels.
Vitamin D recommendations5
Adults, including pregnant and breastfeeding women, and children over four years old should consider taking a daily supplement containing 10 micrograms of vitamin D during autumn and winter. Formula-fed babies should not be given a vitamin D supplement until they're having less than 500ml (about a pint) of infant formula a day, as infant formula is fortified with vitamin D. The following customers are advised to take a daily vitamin D supplement all year round:
- Breastfed babies from birth to one year of age should be given a daily supplement containing 8.5 to 10 micrograms of vitamin D
- Children aged one to four years old should be given a daily supplement containing 10 micrograms of vitamin D
- People who are at increased risk such as those who:
- Are not often outdoors, e.g. if they’re frail, housebound, self-isolating or shielding
- Are in an institution like a care home
- Usually wear clothes that cover up most of their skin when outdoors
- Have dark skin or an African, African-Caribbean or South Asian background.
Vitamin D deficiency
Vitamin D deficiency or vitamin D insufficiency (where the blood level is lower than a healthy level but not low enough to be deficient) is diagnosed by a blood test. Of course, it is not viable to test everyone so recommendations and referral will need to be based on historical supplementation, level of risk and any symptoms present.
Prolonged vitamin D deficiency can result in a condition called rickets in children and a similar condition called osteomalacia in adults, both of which affect bone strength.6 Customers with symptoms of rickets or osteomalacia should be referred to their GP.
Signs and symptoms of rickets
- Pain – the bones affected by rickets can be sore and painful, so the child may be reluctant to walk or may tire easily; the child's walk may look different, e.g. waddling
- Skeletal deformities – thickening of the ankles, wrists and knees, bowed legs, soft skull bones and, rarely, bending of the spine
- Dental problems – including weak tooth enamel, delay
in teeth coming through and increased risk of cavities - Poor growth and development – if the skeleton doesn't grow and develop properly, the child will be shorter than average
- Fragile bones – in severe cases, the bones become weaker and more prone to fractures.
Signs and symptoms of osteomalacia7
- Pain felt in the bones – often in the legs, groin, upper thighs and knees
- Muscle weakness – tends to affect the thighs and the muscles in the shoulders and main trunk of the body
- Slight cracks in the bone (partial fractures).