Vitamin D

Vitamin D is a fat-soluble vitamin that helps the body absorb calcium and phosphate, which are needed for healthy bones, teeth and muscles. Unlike most vitamins, vitamin D can be made by the body: the skin produces it when exposed to ultraviolet B (UVB) light from the sun. Few foods naturally contain much vitamin D, so sunlight, fortified foods and supplements are the main sources for most people, whether or not they follow a vegan diet.

Why vitamin D matters

Severe vitamin D deficiency causes rickets in children and osteomalacia (softening of the bones) in adults. Lower vitamin D status is also linked with weaker bones and an increased risk of fractures. Because vitamin D and calcium work together, both are important for bone health.

Sunlight

The amount of vitamin D made in the skin depends on many factors, including:

• latitude and season – in countries such as the UK, sunlight between roughly October and early March does not contain enough UVB for the skin to make vitamin D;
• time of day and cloud cover;
• skin pigmentation – people with darker skin need longer sun exposure to make the same amount;
• age – the skin makes less vitamin D in older age;
• clothing and sunscreen use;
• time spent indoors.

Sun exposure also carries a risk of skin damage and skin cancer, so health bodies do not recommend deliberate sunbathing as a way to obtain vitamin D.

Recommended intakes

One microgram (µg) of vitamin D equals 40 international units (IU).

D2 and D3

Vitamin D comes in two main forms used in supplements and fortified foods:

• Vitamin D2 (ergocalciferol) is produced by exposing yeast or fungi to UV light. It is vegan.
• Vitamin D3 (cholecalciferol) is the form made in human skin. Commercial D3 is most commonly produced from lanolin, a grease extracted from sheep’s wool, and is therefore not vegan. Some D3 is also derived from fish oil.

Since the 2010s, vegan vitamin D3 derived from lichen has become widely available. Lichens are composite organisms of fungi and algae or cyanobacteria. Lichen-derived D3 is chemically the same as other D3.

Several studies have suggested that D3 may be more effective than D2 at raising and maintaining blood levels of vitamin D, although both forms can correct deficiency. Products labelled simply “vitamin D3” should be assumed to be non-vegan unless they are certified or state that the source is lichen (see vegan certifications and labels).

Vegan food sources

• Fortified foods, including many plant-based milks, yoghurt alternatives, spreads and breakfast cereals. Fortification may use D2 or D3, and some products marketed as vegan use lichen D3.
• UV-exposed mushrooms – mushrooms produce vitamin D2 when exposed to UV light; some are sold specifically treated to raise their vitamin D content.

Unfortified plant foods contain little or no vitamin D. Many non-vegan fortified foods use lanolin-derived D3, which can make fortified products unsuitable for vegans.

Supplementation

Because sunlight is unreliable for much of the year in many countries, health bodies such as the NHS recommend vitamin D supplements for the general population during certain seasons, regardless of diet. Vegans can choose D2 or lichen-derived D3 supplements. Some vegan multivitamins include vitamin D alongside vitamin B12 and iodine.

Safety

Vitamin D is fat-soluble and can accumulate in the body. Excessive intake from supplements can lead to high blood calcium levels (hypercalcaemia), which may damage the kidneys and heart. The NHS advises that adults should not take more than 100 µg (4,000 IU) a day unless advised by a doctor, and the US tolerable upper intake level for adults is also 100 µg. Sunlight does not cause vitamin D toxicity.

This article is for general information. Individuals should consult a doctor or registered dietitian for personal advice, including on testing and supplement dosage.

See also

• Calcium
• Hidden animal ingredients
• Vegan pregnancy and children