Why Vitamin D is important

Vitamin D, often called the “sunshine vitamin”, plays a vital role in keeping us healthy. Yet many people don’t realise just how essential it is—or how common a deficiency can be. From supporting strong bones to helping your immune system function properly, vitamin D is something everyone should be aware of, especially as we get older.

What Does Vitamin D Do in the Body?

Vitamin D is a fat-soluble vitamin that functions more like a hormone. Once activated in the body, it helps regulate the absorption of calcium and phosphate—two minerals crucial for building and maintaining healthy bones and teeth. But its role doesn’t stop there:

• Bone health: Helps the body absorb calcium, making it essential for strong bones and teeth.

• Immune support: Plays a role in your body’s defence against infections.

• Mental wellbeing: Low levels have been linked to mood disorders, including depression.

• Muscle and balance: Helps maintain muscle strength, which can reduce the risk of falls in older adults.

Vitamin D Deficiency, Osteopenia, Osteoporosis – and the Role of Menopause

If your body doesn’t get enough vitamin D, it struggles to absorb calcium effectively. As a result, calcium may be drawn from your bones to maintain normal levels in your blood. Over time, this can lead to:

• Osteopenia: A condition where bone mineral density is lower than normal. It doesn’t always cause symptoms but can be a warning sign.

• Osteoporosis: A more advanced stage where bones become fragile and are more likely to fracture, particularly in the hip, spine and wrist.

  
  

One of the key risk factors for developing osteopenia and osteoporosis—especially in women—is menopause. During menopause, levels of the hormone oestrogen drop significantly. Oestrogen helps protect bones by slowing down the rate of bone loss. When oestrogen levels fall, bone turnover accelerates, increasing the risk of losing bone density rapidly.

Women in the years following menopause are particularly vulnerable, and ensuring adequate vitamin D (along with calcium) becomes even more important to maintain bone strength and reduce fracture risk.

Best Source of Vitamin D: Sunlight

The most efficient source of vitamin D is exposure to sunlight. When UVB rays from the sun hit the skin, they trigger the production of vitamin D. In the UK, this usually happens between late March and early October. Just 10 to 30 minutes of midday sun on your face, arms, or legs a few times a week is often enough—though this depends on skin tone, age, weather, and use of sunscreen.

However, during the autumn and winter months, the sun is not strong enough in most parts of the UK to stimulate vitamin D production. That’s when it becomes especially important to get vitamin D from food or supplements.

Best Food Sources of Vitamin D

Vitamin D is naturally present in only a few foods, but some are excellent sources:

• Oily fish: Salmon, mackerel, sardines, and trout are among the best natural sources.

• Cod liver oil: A traditional supplement rich in both vitamin D and omega-3 fatty acids.

• Egg yolks: Provide small amounts of vitamin D.

• Fortified foods: Many breakfast cereals, plant-based milks (e.g. soya, oat, almond), and some margarines or spreads are fortified with vitamin D.

• UV-exposed mushrooms: Certain mushrooms can produce vitamin D2 when exposed to ultraviolet light.

How to Test Your Vitamin D Levels

If you suspect you’re not getting enough vitamin D, a blood test can check your levels.

The most commonly used test is the:

• 25-hydroxyvitamin D (25(OH)D) blood test

  
  

In the UK, vitamin D levels are typically measured in nanomoles per litre (nmol/L). Here’s a general guide:

• Deficient: Below 25 nmol/L

• Insufficient: 25–50 nmol/L

• Sufficient: 50–125 nmol/L

• High (possibly excessive): Above 125 nmol/L

If your levels are low, your GP or healthcare provider may recommend a high-dose supplement or daily maintenance dose, depending on the severity of the deficiency.

Final Thoughts

Vitamin D plays a central role in maintaining strong bones, supporting your immune system, and protecting against chronic diseases. For women, especially post-menopause, maintaining healthy vitamin D levels is a key part of reducing the risk of osteopenia and osteoporosis, as falling oestrogen levels increase bone loss.

Sunlight remains the most efficient source, but with the limitations of the UK climate, a balanced approach including food sources and supplements—particularly during the darker months—is often necessary.

If you're at risk, recently gone through menopause, or simply unsure about your vitamin D status, it’s worth getting tested. A simple blood test and a few small lifestyle changes can make a lasting difference to your bone health and wellbeing. Contact my clinic if you would like further information on how to test.