Vitamin D

Nine years ago, I discovered just how important vitamin D is when I learned that I was clinically deficient. At the time, I was struggling with joint pain, extreme fatigue, low mood and bowel inflammation. As a natural healthcare practitioner, I had always supported my body through diet, herbs, and therapies, but following the birth of my second child, my recovery wasn’t as strong as I expected.

Wanting to understand what was happening, I gave myself a full health MOT with the support of both my naturopath and my GP. One of the key findings was my low vitamin D status. My results came back at around 20 ng/ml, which is considered clinically deficient.

There’s some debate between functional and conventional medicine about what counts as ‘optimal’ vitamin D levels. Most agree that anything between 30–100 ng/ml is considered adequate, but being just inside the normal range doesn’t always mean your body has enough to function at its best. What I learned from my own experience is that testing your levels is so important and can guide your supplement dose. If you are experiencing any of the below symptoms seek appropriate medical care but also consider checking your vitamin D levels.

Fatigue

Muscle aches and pains

Bone pain

Low mood

Inflammation

Gut issues

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 the sun and small amounts from food. When UV rays reach the skin, they react with a type of cholesterol to create cholecalciferol, the precursor to the active form of vitamin D known as calcitriol. The problem is when you live in the northern hemisphere it can be challenging to get the amount of sun exposure we need especially with the long dark winters and use of sunscreens in the summer.

How much sunlight do we need?

Anywhere between 10–30 minutes of direct sunlight exposure without sunscreen is generally enough to meet daily vitamin D needs, depending on your skin type:

• Fairer skin types: shorter exposure is sufficient.
• Darker skin types: longer exposure may be needed, as higher levels of melanin reduce UV absorption and vitamin D synthesis.

Why is Vitamin D important?

• Vitamin D works in many parts of the body. Its receptors are found in a wide range of cells and help control the activity of hundreds of genes, influencing everything from bone strength to immune function.”
• Vitamin D facilitates the absorption of calcium in the intestines important for bone health, mineralization and growth.
• It supports our immune system by modulating T-helper cells and cytokines as well as stimulating antimicrobial peptides. Research also supports that it can decrease the number of T-cells in autoimmune disease.
• It is important for gut health as it has a regulatory effect on intestinal bacteria.
• It has been linked with cancer prevention due to its modulating effect on genes responsible for cell growth, proliferation and apoptosis.
• Research has shown that vitamin D plays an important role in brain health and emotional wellbeing. Vitamin D receptors are found in areas of the brain involved in mood regulation, and low levels have been linked to symptoms such as sadness, fatigue, and even clinical depression. While the relationship is complex and not fully understood, studies suggest that deficiency may contribute to low mood, and restoring healthy levels can support overall mental health.
  

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.
• High‑risk groups: Babies, children aged 1–4, older adults, people with darker skin, and those who spend little time outdoors should take supplements year‑round.
• Recommended dose: Around 10 micrograms (400 IU) per day for adults, thought this can vary depending on individual health status. I recommend always testing before supplementing, and avoid high levels above 4000 IU without testing first and seeking professional advice.

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.
  

Can anything inhibit vitamin D absorption?

• Low-fat diets: Vitamin D is fat-soluble, so very low-fat meals can reduce absorption. Pairing supplements with healthy fats (olive oil, avocado, nuts) improves uptake.
• Alcohol and caffeine: Excessive intake can impair calcium absorption and disrupt vitamin D metabolism.
• Certain medications: Steroids, weight-loss drugs (like orlistat), and cholesterol-lowering medications can reduce absorption or alter vitamin D metabolism.
• 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, caffeine, and highly processed foods.
• Monitor medications with your healthcare provider if they affect absorption.
• Support gut health for better nutrient uptake.