Vitamin D

All Supplements

Evidence summary

Vitamin D has very strong evidence in this guide. The reference dose is 1000-4000 IU daily, with timing listed as with a meal containing fat. Supplements should support a sound diet and training plan, not replace them.

• Essential for bone health
• Supports immune function

What Is Vitamin D?

Vitamin D is a fat-soluble vitamin that your body produces when your skin is exposed to UVB sunlight. It functions more like a hormone than a traditional vitamin, influencing hundreds of genes and playing a critical role in calcium absorption, bone health, immune function, and muscle performance. Despite being “the sunshine vitamin,” deficiency is incredibly common — especially in the UK and northern latitudes.

How It Works

Vitamin D regulates calcium and phosphorus absorption in the gut, which is essential for maintaining strong bones and teeth. Beyond that, it modulates immune responses, supports muscle contraction, and influences mood through serotonin production. Low levels are associated with increased risk of illness, fatigue, low mood, and impaired recovery from training.

What the Research Says

The evidence for vitamin D supplementation is strong, particularly for people living above the 37th parallel (which includes the entire UK). Public Health England recommends that everyone in the UK consider supplementing during autumn and winter at minimum. Research shows that adequate vitamin D levels support immune function, reduce the risk of stress fractures, and may improve athletic performance in those who are deficient.

How Much Do You Need?

The NHS recommends 400 IU (10mcg) daily as a minimum, but most sports nutrition researchers suggest 1000-4000 IU daily is optimal for active individuals. If you suspect you are significantly deficient, ask your GP for a blood test — the target range is typically 75-125 nmol/L (30-50 ng/mL). Taking it with a meal containing fat improves absorption, as it is fat-soluble.

Who Should Take It

Almost everyone in the UK, particularly from October to March when UVB exposure is insufficient for natural production. People with darker skin, those who work indoors, and anyone who covers most of their skin are at even higher risk of deficiency. If you train hard, adequate vitamin D supports recovery and reduces injury risk.

Who Should Avoid It

Vitamin D toxicity is rare and only occurs at sustained doses above 10,000 IU per day. However, people with certain conditions (hypercalcaemia, sarcoidosis, some kidney diseases) should consult their doctor before supplementing. If you take other medications, check for interactions.

Vegan?

Vitamin D3 (cholecalciferol) is the preferred form, as it raises blood levels more effectively than D2. Most D3 is derived from lanolin (sheep wool grease), which is not vegan. However, lichen-derived D3 is available and equally effective — look for products that specifically state “vegan D3” or “from lichen” on the label.

Where to Buy

• Myprotein Vitamin D3 — from £5.99
• Bulk Vitamin D3 Tablets — from £4.99
• Amazon — Nutravita Vegan Vitamin D3 — from £12.99

Vitamin D: common questions

What is vitamin d used for?

Vitamin D is commonly considered for essential for bone health, supports immune function, may improve mood and energy, most people in the uk are deficient, supports muscle function. The evidence rating in this guide is very strong.

When should I take vitamin d?

The practical timing used in this guide is with a meal containing fat. Consistency and the total daily dose are often more important than a narrow timing window.

How much vitamin d should I take?

The reference dosage in this guide is 1000-4000 IU daily. Individual needs vary, so check the product label and speak to a qualified healthcare professional if you have a medical condition, take medication, are pregnant, or are unsure.

Is vitamin d vegan friendly?

This form of vitamin d can be vegan friendly, but check the capsule, flavouring, and manufacturing details on the specific product.

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