Vitamin D is essential for bone health, immune function, and calcium absorption, yet it poses a unique challenge for those following a vegan diet. With few plant-based food sources available and limited sunlight exposure in the UK, particularly during autumn and winter, vegans are at increased risk of deficiency. Unlike omnivores who obtain vitamin D from oily fish, eggs, and dairy, vegans must rely on fortified foods, supplements, and sunlight. Understanding how to maintain adequate vitamin D status is crucial for preventing bone disorders such as rickets and osteomalacia, supporting immune health, and ensuring long-term wellbeing on a plant-based diet.

Why Vitamin D Matters for Vegans

Vitamin D is a fat-soluble vitamin that functions as a prohormone in the body, essential for calcium absorption, bone health, immune function, and cellular regulation. Unlike many nutrients, vitamin D is not abundant in plant-based foods, making it a nutrient of concern for those following a vegan diet. The primary natural source of vitamin D is sunlight exposure, which triggers synthesis in the skin. However, in the UK, sunlight of sufficient intensity (UVB radiation) is only available between April and September, and even then, factors such as cloud cover, skin pigmentation, sunscreen use, and indoor lifestyles can limit production.

Vegans face a particular challenge: the exclusion of animal products eliminates the main dietary sources of vitamin D (oily fish, egg yolks, and fortified dairy), while relying solely on sunlight is often insufficient, especially during autumn and winter months. Vitamin D₃ (cholecalciferol), the form typically found in animal products, is traditionally derived from lanolin (sheep's wool) or fish, making it unsuitable for vegans unless specifically labelled as plant-derived from lichen.

Deficiency can develop gradually over months to years, leading to impaired bone mineralisation (rickets in children, osteomalacia in adults), increased fracture risk, and potentially compromised immune function. The NHS recommends that everyone in the UK should consider taking a daily supplement containing 10 micrograms of vitamin D during autumn and winter months. Those who have very little sun exposure or have darker skin may benefit from year-round supplementation. For vegans, maintaining adequate vitamin D status requires particular attention due to the limited dietary sources available.

Vegan Sources of Vitamin D

Natural vegan food sources of vitamin D are extremely limited. Wild mushrooms exposed to sunlight contain small amounts of vitamin D₂ (ergocalciferol), and some commercially grown mushrooms are now treated with UV light to enhance their vitamin D content. However, the amounts can vary considerably, so check product packaging for specific values. Research suggests that vitamin D₂ is generally less effective at raising and maintaining serum 25-hydroxyvitamin D levels compared to vitamin D₃, though it still contributes to overall status.

The most reliable vegan sources are fortified foods, which have become increasingly available in response to growing plant-based dietary patterns. Common fortified products include:

• Plant-based milk alternatives (soya, oat, almond, coconut) – typically providing around 0.75–1.5 micrograms per 100ml, though amounts vary by brand

• Breakfast cereals – many contain added vitamin D, though amounts vary considerably

• Plant-based spreads and margarines – often fortified with vitamin D (butter contains only small natural amounts)

• Fortified nutritional yeast – some brands include vitamin D alongside B vitamins

• Vegan yoghurt alternatives – increasingly fortified with calcium and vitamin D

It is essential to check product labels, as fortification is not universal and the form of vitamin D used varies. Some manufacturers now use vegan vitamin D₃ derived from lichen, which appears to be more effective than D₂ for maintaining optimal levels. However, even with careful selection of fortified foods, achieving the recommended daily intake through diet alone remains challenging for most vegans. Research suggests that vegans typically have lower vitamin D status than omnivores, highlighting the importance of supplementation alongside dietary sources.

How Much Vitamin D Do You Need?

The UK government's Scientific Advisory Committee on Nutrition (SACN) recommends a Reference Nutrient Intake (RNI) of 10 micrograms (400 IU) daily for everyone aged four years and above, including pregnant and breastfeeding women. This recommendation assumes minimal sunlight exposure and is designed to maintain serum 25-hydroxyvitamin D concentrations above 25 nmol/L in 97.5% of the population—the threshold below which bone health may be compromised.

While 10 micrograms daily is the UK recommendation, some international bodies suggest higher intakes. Individual requirements vary based on factors such as sun exposure, skin pigmentation, age, and dietary patterns. If you're concerned about your vitamin D status, consult a healthcare professional for personalised advice.

Special considerations apply to certain groups:

• Infants and young children: Breastfed babies should receive 8.5–10 micrograms daily from birth to one year, as breast milk contains minimal vitamin D. Babies consuming more than 500ml of infant formula daily do not need supplements as formula is already fortified. Children aged 1-4 years should take a daily 10 microgram supplement year-round.

• Older adults: Those over 65 may have reduced skin synthesis capacity and benefit from year-round supplementation

• Individuals with darker skin: Higher melanin levels reduce UVB penetration, making year-round supplementation advisable

• Those with limited sun exposure: Including people who are housebound, cover their skin for cultural or religious reasons, or work predominantly indoors

Vitamin D is fat-soluble and can accumulate in body tissues. Whilst toxicity is rare, the NHS advises not exceeding 100 micrograms (4,000 IU) daily for adults. For children, upper limits are lower: 25 micrograms daily for infants under 1 year and 50 micrograms daily for children aged 1-10 years. Always follow product guidance and consult a healthcare professional before exceeding recommended doses.

Choosing the Right Vitamin D Supplement

Selecting an appropriate vitamin D supplement requires consideration of several factors, particularly for vegans. The most important distinction is between vitamin D₂ (ergocalciferol) and vitamin D₃ (cholecalciferol). Traditionally, D₃ has been derived from animal sources, making it unsuitable for vegans, whilst D₂ is plant-derived from yeast or mushrooms. However, vegan vitamin D₃ extracted from lichen is now widely available and represents a good choice, as research indicates that D₃ is more effective at raising and sustaining serum 25-hydroxyvitamin D levels than D₂.

When selecting a supplement, look for products that:

• Clearly state "suitable for vegans" and display recognised vegan certification (Vegan Society, Vegetarian Society)

• Specify vitamin D₃ from lichen rather than D₂, where possible

• Provide 10 micrograms (400 IU) in line with UK recommendations

• Are from reputable manufacturers with clear labelling and quality assurances (such as GMP, BRC, ISO or UKAS accreditation)

• Contain minimal additives and avoid unnecessary fillers or allergens

Vitamin D supplements are available in various formulations including tablets, capsules, oral sprays, and liquid drops. As vitamin D is fat-soluble, absorption may be enhanced when taken with food containing some fat, though modern formulations are generally well-absorbed regardless. Some products combine vitamin D with other nutrients such as calcium or vitamin K₂, though these combinations are not routinely recommended by the NHS for everyone.

Timing and consistency matter more than the specific formulation. Taking your supplement at the same time daily—many people find morning with breakfast most convenient—helps establish a routine and ensures regular intake. If you miss a dose occasionally, simply resume your normal schedule rather than doubling up.

Seek medical advice before taking vitamin D supplements if you have a history of kidney stones, hypercalcaemia, sarcoidosis, severe kidney or liver disease, or if you take certain medications (including thiazide diuretics or digoxin). If you experience any suspected adverse reactions to vitamin D medicines, report them via the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).

Signs of Vitamin D Deficiency

Vitamin D deficiency often develops gradually and may remain asymptomatic in its early stages, making it particularly insidious. When symptoms do manifest, they can be non-specific and easily attributed to other causes. Common presentations include:

• Bone and muscle pain: Diffuse musculoskeletal discomfort, particularly in the lower back, pelvis, and legs

• Muscle weakness: Particularly affecting proximal muscles (thighs, upper arms), which may cause difficulty climbing stairs or rising from a chair

• Fatigue: Some people report persistent tiredness, though this is non-specific and has many potential causes

• Frequent infections: Vitamin D plays a role in immune function, though evidence linking deficiency directly to increased infection risk remains inconclusive

• Low mood: Some studies suggest an association between vitamin D deficiency and depression, though causality has not been definitively established

Severe or prolonged deficiency can lead to more serious complications. In children, this manifests as rickets—characterised by delayed growth, bone pain, skeletal deformities (bowed legs, widened wrists and ankles), and dental problems. In adults, osteomalacia develops, causing bone pain, tenderness, and increased fracture risk, particularly affecting the spine, pelvis, and lower limbs. A characteristic feature is a waddling gait due to proximal muscle weakness.

It is important to recognise that many of these symptoms are non-specific and can result from numerous other conditions. If you experience persistent bone pain or tenderness, unexplained muscle weakness, recurrent fractures, or gait disturbance, consult your GP promptly. Blood testing is required to confirm vitamin D status, and other potential causes must be excluded. Never assume symptoms are solely due to vitamin D deficiency without proper medical assessment.

Getting Your Vitamin D Levels Tested

Vitamin D status is assessed by measuring serum 25-hydroxyvitamin D [25(OH)D], the major circulating form that reflects both dietary intake and endogenous synthesis. In the UK, testing is not routinely offered to the general population or to asymptomatic individuals in at-risk groups, as universal supplementation recommendations are considered more cost-effective.

According to NICE guidance, testing may be appropriate for individuals with:

• Symptoms suggestive of deficiency (bone pain, muscle weakness, fractures)

• Conditions affecting vitamin D metabolism (chronic kidney disease, malabsorption disorders, liver disease)

• Medications that interfere with vitamin D metabolism (certain anticonvulsants, glucocorticoids)

• Before starting treatment with high-dose vitamin D

If you have symptoms that might indicate deficiency, discuss this with your GP, who can arrange an NHS blood test if clinically indicated. The test is not universally available on the NHS for screening purposes in asymptomatic individuals. Private testing is available through various providers, typically costing £25–60 for a finger-prick home test kit.

Interpreting results (UK reference ranges):

• <25 nmol/L: Deficient—treatment required

• 25–50 nmol/L: Insufficient—supplementation recommended

• >50 nmol/L: Sufficient for most people according to UK guidance

If deficiency is confirmed, your GP may prescribe higher-dose supplementation. UK treatment regimens typically involve a loading dose totalling approximately 300,000 IU over 6-10 weeks (e.g., 50,000 IU weekly for 6 weeks or 20,000 IU twice weekly for 7-8 weeks), followed by maintenance therapy of 800-2,000 IU daily. For vegans, be aware that many licensed high-dose vitamin D preparations are derived from animal sources. Discuss vegan alternatives with your healthcare provider if this is important to you. Repeat testing after three to four months of supplementation may be advised to confirm adequate response. Remember that maintaining consistent supplementation is more important than repeated testing for most individuals.

Frequently Asked Questions