Vitamin D

10 years ago, I discovered just how important vitamin D could be to our health when I was diagnosed with a deficiency. At the time, I was struggling with joint pain, extreme fatigue, low mood and bowel inflammation. As a natural healthcare practitioner, I had always tried to support my health through nutrition, herbs and complementary therapies. However, following the birth of my second child, my recovery wasn’t as straightforward as I had expected.

Wanting to understand what was happening, I decided to have a thorough health MOT, working alongside both my naturopath and GP. One of the key findings was that my vitamin D levels were clinically deficient.

Vitamin D plays an important role in calcium absorption, bone health, muscle function and immune system function. Research has also explored its relationship with mood and inflammation, although the links are complex and the evidence is still evolving.

There is ongoing discussion about what constitutes an optimal vitamin D level, particularly between conventional and functional medicine. While some practitioners advocate higher target levels, there is no universally agreed optimal range for every individual. A result also needs to be interpreted in the context of the laboratory reference range, your symptoms and your overall health. If you are experiencing any of the below symptoms seek appropriate medical care but also consider checking your vitamin D levels.

• Persistent fatigue
• Muscle aches, weakness or pains
• Bone pain or tenderness
• Low mood
• Slow wound healing

Vitamin D & your health

Vitamin D is a fat-soluble vitamin that supports many vital functions in the body. Ideally, we obtain most of our vitamin D from sunlight, with smaller amounts from food. When UVB rays reach the skin, they trigger the production of cholecalciferol (vitamin D3), the precursor to the active form of vitamin D known as calcitriol.

However, living in the northern hemisphere can make it difficult to produce enough vitamin D, particularly during the long, dark winter months when sunlight is insufficient. Our vitamin D production can also be influenced by how much time we spend outdoors, clothing and sunscreen use.

How much sunlight do we need?

The amount of sunlight needed to produce vitamin D varies depending on skin tone, time of year, time of day and how much skin is exposed. Fairer skin generally produces vitamin D more quickly, while darker skin contains more melanin, which reduces vitamin D production.

In the UK, sunlight is generally insufficient for vitamin D production during autumn and winter. During spring and summer, short periods outdoors may help maintain vitamin D levels, but there is no single exposure time that works for everyone and it can be a fine line between exposing your skin to sunlight and protecting it at the same time.

Why is Vitamin D important?

Vitamin D plays a vital role in many processes throughout the body. Vitamin D receptors are found in numerous tissues, and the vitamin influences the activity of genes involved in a wide range of biological functions.

• Bone health: Vitamin D helps the body absorb calcium from the intestines, supporting healthy bones, teeth and normal bone mineralisation.
• Immune function: Vitamin D helps regulate immune responses, including the activity of immune cells and the production of antimicrobial substances that help defend the body against infection.
• Gut health: Vitamin D helps maintain the intestinal barrier and influences immune activity in the gut. Research into its relationship with the gut microbiome is ongoing.
• Brain health and mood: Vitamin D receptors are found in areas of the brain involved in mood regulation. Low vitamin D levels have been associated with depression and fatigue, although this does not necessarily mean deficiency is the cause, it may indicate that maintaining adequate vitamin D levels form a wider part of the picture when supporting overall health and wellbeing.

Can anything inhibit vitamin D absorption?

• Excessive Alcohol may effect nutrient status.
• Certain medications can impact vitamin D absorption, if this a concern it should be discussed with your healthcare professional.
• Digestive conditions: Crohn’s disease, celiac disease, and other gut disorders can impair fat absorption, which is essential for vitamin D uptake.
• Age and liver/kidney health: Older adults and those with liver or kidney disease may struggle to convert vitamin D into its active form.

Practical tips to improve absorption

• Take vitamin D supplements with a meal containing healthy fats.
• Limit excessive alcohol.
• Monitor medications with your healthcare provider if they affect absorption.
• Support gut health for better nutrient uptake.
• Eat a varied diet that includes sources of vitamin D.
  

Can I get vitamin D from food?

Yes, you can get vitamin D from food sources such as oily fish, eggs, mushrooms, and fortified products. However, diet alone usually does not provide enough vitamin D to meet daily requirements, especially in regions with limited sunlight. Here are some food sources below:

• Salmon, mackerel, sardines, and tuna are among the richest natural sources.
• Egg yolks: Contain small amounts of vitamin D.
• Mushrooms: Especially those exposed to UV light, which increases their vitamin D content.
• Fortified foods: Many dairy products, plant milks, breakfast cereals, and spreads have vitamin D added during manufacturing.
• Liver: Beef liver provides modest amounts.

Do I need to take a supplement?

NHS Guidelines on Supplementation:

• Seasonal advice: Everyone should consider a daily supplement in autumn and winter, when sunlight is too weak for vitamin D production.
• Recommended dose: Around 10 micrograms (400 IU) per day for adults, though this can vary depending on individual health status. If you have a diagnosed deficiency or certain medical condition a different dose may be required.

Variability in Supplements

• Vitamin D2 vs D3:
• D3 (cholecalciferol) is generally more effective at raising blood levels.
• D2 (ergocalciferol) is less potent and less stable.
• Formulation matters:
• Oil‑based capsules often have better absorption than dry tablets, since vitamin D is fat‑soluble.
• Some products combine vitamin D with calcium, which may be useful for bone health but not always necessary.
• Quality differences: Independent testing shows that supplement brands vary in accuracy of labelling, purity, and bioavailability. Seek professional guidance on trusted brands.