Vitamin D: The Sunshine Supplement You Shouldn’t Ignore

What Is Vitamin D?

Let’s start with the basics; vitamin D is a fat-soluble nutrient that our skin produces when it’s exposed to sunlight. Technically, it acts more like a hormone than a true vitamin because our bodies can make it naturally.

Vitamin D helps us absorb calcium, magnesium, and phosphate from food which are all vital for strong bones and healthy teeth. It also plays a role in muscle function, immune support, and reducing inflammation.

Historically, vitamin D was discovered during research into rickets, a childhood bone-softening disease caused by deficiency. Today, supplementation remains key for both prevention and treatment.

While sunlight is our best source, vitamin D is also found in small amounts in food (mainly fatty fish like salmon, trout, tuna, and mackerel). Tiny amounts are present in egg yolks, beef liver, cheese, and UV-exposed mushrooms, but diet alone usually isn’t enough.

How Do We Make Vitamin D?

Our skin produces vitamin D when UVB rays from the sun reach it directly. Just 20–30 minutes of full-body exposure can produce around 20,000 IU, far more than the NHS’s daily supplement guideline of 400 IU.

However, a few important points:

• Sunscreen blocks UVB rays, which means no vitamin D is made while it’s on your skin.

• At least 25% of your skin needs to be uncovered (e.g. arms and legs) for good production.

• Sunbeds don’t help, as they mainly emit UVA light.

• In the UK, vitamin D can only be made between April and September, and roughly between 11 a.m. and 4 p.m.

A quick tip: if your shadow is shorter than you, your body can make vitamin D! During UK winters, this rarely happens, meaning most of us can’t make enough between October and March.

Vitamin D Deficiency — How Common Is It?

By the end of winter, around 87% of people in the UK have low vitamin D levels, and surprisingly, up to 60% remain low even after summer. Office jobs, cloudy days, and sunscreen use all reduce exposure.

The best strategy?

• Get 20–30 minutes of midday sun on bare skin in summer before applying sunscreen.

• In winter, supplement daily.

Understanding Blood Levels

NHS considers 50 nmol/L or higher to be an acceptable vitamin D level. However, many practitioners working in functional health aim for 100–150 nmol/L, where most people feel their best.

Signs You Might Be Low

Deficiency isn’t always obvious, but common symptoms can include:

• Fatigue or low energy

• Muscle or joint pain

• Persistent back or neck discomfort

• Headaches or migraines

• Low mood, anxiety, or brain fog

Children who complain of “growing pains” may also be showing signs of deficiency so it’s worth getting their vitamin D checked.

Who’s Most at Risk?

Some groups find it harder to make or use vitamin D efficiently:

• Older adults, as the skin becomes less effective at producing it

• People with darker skin, since higher melanin reduces UV absorption

• Individuals with higher body fat, as vitamin D is stored in fat tissue

Interestingly, these same groups were also identified as being more at risk of complications during COVID-19, which led to renewed research into vitamin D’s role in immunity.

Supplementation

For anyone living in Britain, a vitamin D supplement is essential through the winter months. If you spend most of your time indoors, it’s also worth continuing through summer.

The NHS recommends 400 IU daily for general use. However, functional medicine practitioners often suggest higher doses depending on your age, weight, and health.

Sublingual (under-the-tongue) sprays or drops are absorbed more efficiently than standard tablets, and are a great option for daily use.

Typical ranges used by practitioners:

• Toddlers: 1,000 IU

• 4–8 years: 2,000 IU

• 8–12 years: 3,000 IU

• Teenagers: 3,000–5,000 IU

• Adults: 4,000–5,000 IU

• Adults 3st+ overweight: 7,000–8,000 IU

• Adults 5st+ overweight: 10,000 IU

(Always consult your healthcare provider before taking higher-dose supplements.)

Contraindications & Combinations

If you have certain conditions, you should not take vitamin D without medical advice, for example, sarcoidosis. Those on Warfarin should avoid supplements containing vitamin K.

Vitamin D works best alongside vitamin K2, magnesium, and vitamin B6, which help your body utilise it properly and direct calcium to the right places (bones, not arteries!).

Our Recommendation at Thrive Chiropractic

At Thrive Chiropractic, I encourage all our patients to maintain healthy vitamin D levels throughout the year. I stock a high-quality chewable supplement (4,000 IU per dose) that tastes great and supports your whole family’s wellbeing.

If you’re unsure what dosage is right for you, speak to me and I’ll help you find what’s best for your body and lifestyle.