Vitamin D is essential for bone health, immune function, and calcium regulation, yet obtaining adequate amounts from plant-based foods presents significant challenges for vegetarians and vegans. Unlike animal products such as oily fish and eggs, vegetables contain negligible vitamin D, with mushrooms exposed to ultraviolet light being the only meaningful plant source. In the UK, where sunlight is insufficient for vitamin D synthesis between October and March, the NHS recommends that everyone consider taking a daily 10-microgram supplement during autumn and winter. For those following plant-based diets, fortified foods and year-round supplementation become particularly important strategies to prevent deficiency and maintain optimal vitamin D status.

Understanding Vitamin D and Plant-Based Sources

Vitamin D is an essential fat-soluble vitamin that plays a crucial role in maintaining bone health, supporting immune function, and regulating calcium and phosphate metabolism in the body. Unlike most vitamins, vitamin D functions as a prohormone, with the body capable of synthesising it when skin is exposed to ultraviolet B (UVB) radiation from sunlight. However, in the UK, sunlight intensity is insufficient for adequate vitamin D synthesis between October and early March, making dietary sources and supplementation particularly important.

For individuals following vegetarian or vegan diets, obtaining sufficient vitamin D presents unique challenges. The most bioavailable form of vitamin D in food is vitamin D3 (cholecalciferol), which is predominantly found in animal-derived products such as oily fish, egg yolks, and meat. Plant-based foods naturally contain very limited amounts of vitamin D, and when present, it is typically in the form of vitamin D2 (ergocalciferol), which research suggests may be less effective at raising blood levels of 25-hydroxyvitamin D—the marker used to assess vitamin D status.

The UK government recommends a daily intake of 10 micrograms (400 IU) for adults and children over one year of age. For breastfed infants under one year, 8.5-10 micrograms daily is recommended, while formula-fed infants consuming more than 500ml of infant formula daily usually receive sufficient vitamin D. Vitamin D deficiency can lead to rickets in children and osteomalacia in adults, conditions characterised by bone softening and increased fracture risk. Understanding the limited natural plant sources of vitamin D is the first step in developing an effective strategy to maintain adequate levels whilst adhering to a plant-based dietary pattern.

Which Vegetables and Plant Foods Contain Vitamin D?

The reality for those seeking vitamin D from vegetables is somewhat disappointing: conventional vegetables contain negligible or no vitamin D. Leafy greens, root vegetables, legumes, and most fruits do not naturally synthesise or accumulate vitamin D in meaningful quantities. This is a fundamental difference between plant and animal metabolism, as animals can store vitamin D in their tissues, particularly in fatty fish and liver.

However, there are a few notable exceptions within the broader plant kingdom. Mushrooms represent the only significant natural plant-based source of vitamin D. When exposed to ultraviolet light—either naturally through sunlight or artificially during cultivation—mushrooms can convert ergosterol in their cell membranes to vitamin D2 (ergocalciferol). The vitamin D content varies considerably depending on the species and UV exposure:

• UV-exposed mushrooms: Some commercially available mushrooms are specifically treated with UV light and can contain 5–10 micrograms of vitamin D2 per 100g serving, potentially meeting daily requirements

• Wild mushrooms: Varieties such as chanterelles and morels naturally exposed to sunlight may contain moderate amounts of vitamin D2, though foraging wild mushrooms is not recommended unless you have proper training due to poisoning risks

• Standard cultivated mushrooms: Those grown in darkness (the typical commercial method) contain minimal vitamin D, often less than 0.1 micrograms per 100g

Certain algae and lichen also produce vitamin D, though these are not typically consumed as vegetables. Some species of algae can synthesise vitamin D3, which has led to their use in vegan supplement formulations. It is important to note that whilst mushrooms can contribute to vitamin D intake, relying solely on standard shop-bought mushrooms without UV treatment would require consuming impractically large quantities to meet daily requirements.

Meeting Your Vitamin D Needs on a Vegetarian or Vegan Diet

Given the scarcity of natural vitamin D in plant foods, individuals following vegetarian or vegan diets must adopt a multifaceted approach to maintain adequate vitamin D status. Sunlight exposure remains the primary natural source for most people, regardless of dietary pattern. During spring and summer months (late March to September in the UK), spending short periods outdoors with forearms, hands, or lower legs exposed several times per week can support vitamin D synthesis. However, it's important to follow sun safety guidance and avoid burning. Factors including skin pigmentation, age, latitude, time of day, weather conditions, and sunscreen use all significantly affect synthesis efficiency.

For vegetarians who consume dairy products and eggs, these foods can provide modest contributions to vitamin D intake. A large egg contains approximately 1–2 micrograms of vitamin D3, whilst standard milk and cheese contain minimal amounts unless fortified. Lacto-ovo vegetarians therefore have a slight advantage over vegans but still face challenges meeting requirements through diet alone, particularly during winter months.

Vegans must be particularly vigilant, as their dietary options are severely restricted without fortification. Those with symptoms of deficiency should consult their GP, who may recommend testing vitamin D levels. Risk factors for vitamin D deficiency include:

• Limited sun exposure due to indoor lifestyle, cultural dress practices, or mobility limitations

• Darker skin pigmentation, which reduces cutaneous vitamin D synthesis

• Older age (over 65 years), as skin synthesis efficiency declines

• Living in care homes or being housebound

• Obesity (BMI over 30)

• Conditions affecting fat absorption, such as coeliac disease or inflammatory bowel disease

• Kidney or liver disease

• Taking certain medicines (including enzyme-inducing antiepileptics, rifampicin, glucocorticoids, cholestyramine, orlistat)

The NHS recommends that everyone, regardless of diet, should consider taking a daily supplement containing 10 micrograms of vitamin D during autumn and winter months. Children aged 1-4 years should take a 10 microgram supplement year-round. Year-round supplementation is also advised for at-risk groups with limited sun exposure.

Fortified Foods and Supplements for Vegetarians

Food fortification represents the most practical strategy for vegetarians and vegans to achieve adequate vitamin D intake through diet. In the UK, an increasing range of plant-based products are voluntarily fortified with vitamin D, though fortification is not mandatory for most foods (with the exception of infant formula). When selecting fortified products, it is essential to check labels carefully, as vitamin D content varies considerably between brands and product types.

Commonly fortified plant-based foods include:

• Plant-based milk alternatives: Soya, oat, almond, and coconut drinks are frequently fortified with 0.75–1.5 micrograms per 100ml, providing approximately 1.9–3.8 micrograms per 250ml serving

• Breakfast cereals: Many brands add vitamin D alongside other nutrients, typically providing 1.3–4.2 micrograms per serving

• Plant-based spreads and margarines: Often fortified with vitamin D2 or D3, typically providing around 0.3–1 microgram per 10-20g serving (check labels as content varies by brand)

• Plant-based yoghurt alternatives: Increasingly available with added vitamin D, though content varies

• Nutritional yeast: Some brands are fortified with B vitamins and vitamin D

Supplementation offers the most reliable method to ensure adequate intake. Vitamin D supplements are available in two forms: D2 (ergocalciferol), which is always suitable for vegans, and D3 (cholecalciferol), which is traditionally derived from lanolin (sheep's wool) but is now also available from lichen sources for vegans. Research suggests vitamin D3 may be more effective at raising and maintaining blood levels, though both forms are considered acceptable.

Most vitamin D supplements are regulated as food supplements under food law, while high-dose vitamin D products are regulated as medicines by the Medicines and Healthcare products Regulatory Agency (MHRA). Standard over-the-counter supplements typically contain 10 micrograms (400 IU) or 25 micrograms (1,000 IU) per dose. The UK safe upper limits are 100 micrograms (4,000 IU) daily for adults and children over 11 years, 50 micrograms daily for children aged 1-10 years, and 25 micrograms daily for infants under 1 year. Excessive vitamin D intake can lead to hypercalcaemia, with symptoms including nausea, weakness, and kidney problems. Seek medical advice before taking high-dose supplements if you have conditions such as kidney disease, sarcoidosis or hyperparathyroidism, or if you take medicines including thiazide diuretics or digoxin. If you experience side effects from vitamin D medicines, report them via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

NHS Guidance on Vitamin D for Plant-Based Diets

The NHS provides clear, evidence-based guidance on vitamin D that applies to all dietary patterns, with particular relevance for those following plant-based diets. The UK government recommends that everyone aged one year and above should consider taking a daily supplement containing 10 micrograms (400 IU) of vitamin D during autumn and winter (October to early March). This recommendation acknowledges that sunlight exposure is insufficient for adequate vitamin D synthesis during these months in the UK, regardless of dietary choices.

For individuals at higher risk of deficiency—including those following strict vegan diets with limited fortified food consumption—year-round supplementation is advised. The NHS specifically identifies people who are not often outdoors, those who cover their skin when outside, and individuals with dark skin as requiring particular attention to vitamin D status. For breastfed infants, a daily supplement of 8.5-10 micrograms is recommended from birth, while formula-fed infants consuming more than 500ml daily usually receive sufficient vitamin D. Children aged 1-4 years should take a daily 10 microgram supplement year-round.

NICE guidance (Clinical Knowledge Summary on Vitamin D Deficiency) outlines investigation and management protocols. Vitamin D deficiency is defined as serum 25-hydroxyvitamin D below 25 nmol/L, with insufficiency between 25–50 nmol/L. Routine testing of vitamin D levels is not recommended for asymptomatic people, even in at-risk groups. Testing is typically reserved for those with symptoms of deficiency or before starting high-dose treatment. Treatment regimens for confirmed deficiency typically involve loading doses followed by maintenance therapy, with specific protocols varying based on severity and patient factors.

Patients should contact their GP if they experience symptoms potentially related to vitamin D deficiency, including:

• Persistent bone or muscle pain

• Frequent fractures or bone tenderness

• Muscle weakness or difficulty with physical activities

• Unexplained fatigue

• Mood changes or low mood

Pregnant and breastfeeding women following plant-based diets should take a daily 10 microgram vitamin D supplement, the same as the general adult recommendation. The NHS Healthy Start scheme provides free vitamins, including vitamin D, to eligible pregnant women and families with young children. For those following vegetarian or vegan diets, ensuring adequate vitamin D status requires proactive planning, combining sensible sun exposure when possible (following sun safety guidance), regular consumption of fortified foods, and appropriate supplementation as recommended by current NHS guidance.

Frequently Asked Questions