London Osteoporosis Clinic · Course 5

Vitamin D – Absorption and Bone Health

Welcome to the Vitamin D – Absorption and Bone Health module.

Vitamin D is essential for healthy bones, strong muscles and overall wellbeing. Yet vitamin D deficiency is common, often without obvious symptoms, and can quietly increase the risk of osteoporosis, fractures and falls.

In this module you will discover:

• Why vitamin D matters and how it supports lifelong bone health.
• How sunlight, food and supplements contribute to healthy vitamin D levels.
• Who is more likely to become vitamin D deficient.
• What practical, evidence-based steps you can take to optimise your vitamin D safely.

Our aim is not simply to provide information, but to help you understand your own risk and take confident action to protect your future bone health.

The information in this course is educational and should not replace personalised medical advice. If you are concerned about your vitamin D levels or bone health, please speak to your healthcare professional.

For further resources and specialist support, visit londonosteoporosisclinic.com.

Dr Taher Mahmud has spent more than two decades helping people prevent fractures, improve bone health and remain active throughout life. This course combines clinical experience with current evidence to help you make informed decisions and build lasting health capability.

We hope you finish this module feeling more informed, more confident and empowered to take practical steps towards stronger bones and healthier ageing.

Why this matters

Vitamin D is one of the most important nutrients for maintaining strong bones, healthy muscles and lifelong mobility. Because vitamin D deficiency often develops without obvious symptoms, many people are unaware that they may be increasing their risk of osteoporosis, falls and fractures.

Understanding your vitamin D status is one of the simplest steps you can take to protect your future health.

Understanding vitamin D

Vitamin D helps your body absorb calcium and phosphorus—the minerals needed to build, maintain and repair bone.

Without enough vitamin D, calcium absorption falls, even when your diet contains enough calcium. Over time this can weaken bones, reduce muscle strength and increase the likelihood of falls and fractures.

Vitamin D also supports:

• Healthy bones throughout life
• Strong muscles and better balance
• Normal immune function
• Bone repair and remodelling

Most vitamin D is produced when sunlight reaches the skin. However, many factors reduce vitamin D production, including:

• Spending more time indoors
• Living in northern countries such as the UK
• Older age
• Darker skin pigmentation
• Obesity
• Limited sun exposure

As a result, vitamin D deficiency is common.

What you can do

Optimising your vitamin D level is a practical step that supports lifelong bone health. Depending on your individual circumstances, this may include sensible sunlight exposure, vitamin D-rich foods or supplementation.

Remember that vitamin D works as part of a wider bone health strategy that also includes adequate calcium, sufficient protein, regular weight-bearing and strength exercise, and healthy lifestyle habits.

There are three main ways your body obtains vitamin D:

🌞 1. Sunlight

For most people, sunlight is the most important source of vitamin D. When ultraviolet B (UVB) rays from the sun reach your skin, your body naturally produces vitamin D.

🥗 2. Food

A small amount of vitamin D comes from the foods you eat. Good dietary sources include:

• Oily fish such as salmon, mackerel and sardines
• Egg yolks
• Liver
• Fortified foods, including some breakfast cereals, dairy products and plant-based alternatives

Although a healthy diet contributes to vitamin D intake, it is usually not enough on its own to maintain adequate levels.

💊 3. Supplements

Many people benefit from taking a vitamin D supplement, particularly during the autumn and winter months or if they have limited sun exposure. Your healthcare professional can advise on the most appropriate dose for your individual circumstances.

Should You Have Your Vitamin D Level Checked?

A simple blood test can measure your vitamin D level. Testing is particularly useful if you have osteoporosis, are at increased risk of deficiency, or have symptoms that may be related to low vitamin D.

Knowing your vitamin D level allows your healthcare professional to recommend the most appropriate combination of sunlight exposure, dietary changes and supplementation to help you achieve and maintain healthy levels.

How Much Sunlight Do We Need?

Sunlight is the body's main natural source of vitamin D. When ultraviolet B (UVB) rays reach your skin, they trigger the production of vitamin D.

The amount of sunlight needed varies considerably depending on:

• The time of year
• Time of day
• Latitude (where you live)
• Cloud cover and air pollution
• Your age
• Skin colour
• The amount of skin exposed

For many people in the UK during spring and summer, short periods of sunlight on bare skin several times each week are enough to help maintain healthy vitamin D levels. However, there is no single exposure time that is suitable for everyone.

Finding the Right Balance

Sunlight has many health benefits, but it is important to avoid sunburn.

General advice includes:

• Spend some time outdoors most days where possible.
• Expose your forearms, lower legs or other areas of skin when it is safe to do so.
• Avoid prolonged sun exposure that causes reddening or burning.
• Apply sunscreen if you are staying in the sun for longer periods. Although sunscreen can reduce vitamin D production, protecting your skin from sun damage remains the priority.

Who May Need More Sunlight?

Some people produce vitamin D less efficiently and are more likely to become deficient, including those who:

• Have darker skin pigmentation.
• Spend most of their time indoors.
• Regularly cover most of their skin with clothing.
• Live in care homes or are housebound.
• Are older adults.

Many of these individuals will benefit from vitamin D supplementation, particularly during the autumn and winter months.

Why Is Vitamin D Stored?

Vitamin D is a fat-soluble vitamin, along with vitamins A, E and K. After it is produced in the skin or absorbed from food, it is stored in the body's fat and liver, allowing it to be used when sunlight exposure is reduced.

Living in the UK

In the UK, sunlight is generally not strong enough between October and early March for most people to produce adequate amounts of vitamin D. Modern lifestyles also mean that many people spend much less time outdoors than previous generations.

For these reasons, vitamin D deficiency is common, making sensible sunlight exposure, a healthy diet, appropriate supplementation and, where appropriate, blood testing important parts of maintaining lifelong bone health.

Although sunlight is the body's main source of vitamin D, certain foods can also help you maintain healthy vitamin D levels.

However, it is important to understand that diet alone is unlikely to provide enough vitamin D for most people, particularly in the UK. Food should be seen as part of an overall strategy that includes sensible sunlight exposure and, for many people, vitamin D supplements.

Foods Naturally Rich in Vitamin D

Good natural sources include:

• Oily fish, such as salmon, mackerel, sardines and herring.
• Egg yolks.
• Liver (although this should be eaten in moderation).
• Cod liver oil.

Fortified Foods

Many everyday foods have vitamin D added to them, including some:

• Breakfast cereals.
• Dairy products.
• Plant-based milk alternatives.
• Fat spreads (such as margarine).
• Orange juice (in some countries).

Always check the food label, as vitamin D fortification varies between products.

Is Food Enough?

For many people, particularly those living in northern countries such as the UK, obtaining enough vitamin D from food alone is difficult.

Children, older adults, people with darker skin, those who spend little time outdoors, and individuals with osteoporosis may all require vitamin D supplements to maintain healthy levels.

A simple blood test can determine whether your vitamin D level is adequate and help guide the most appropriate treatment.

For many people, vitamin D supplements provide a simple and effective way to maintain healthy vitamin D levels throughout the year.

In the UK, the Department of Health and Social Care recommends that:

• Everyone aged 1 year and over should consider taking a daily supplement containing 10 micrograms (400 IU) of vitamin D during the autumn and winter months.
• This advice also applies to pregnant and breastfeeding women.
• People who spend little time outdoors, have darker skin, cover most of their skin, live in care homes, or are otherwise at increased risk of vitamin D deficiency may benefit from taking vitamin D throughout the year.

While these recommendations are appropriate for the general population, some people—particularly those with osteoporosis, a confirmed vitamin D deficiency or certain medical conditions—may require different doses. A simple blood test can help determine the most appropriate treatment for you.

Measure Rather Than Guess

At the London Osteoporosis Clinic, we encourage people to measure rather than guess whenever possible.

A simple blood test can determine whether your vitamin D level is adequate and help your healthcare professional recommend the most appropriate dose. This helps avoid both under-treatment and unnecessarily high doses.

Choosing a Supplement

When selecting a vitamin D supplement, look for products from reputable manufacturers that:

• Clearly state the amount of vitamin D provided.
• Are produced to recognised quality standards.
• Provide vitamin D3 (cholecalciferol), unless another form has been specifically recommended for you.

Many people ask whether they should also take vitamin K2. Although this combination is increasingly popular, it is not necessary for everyone. Your healthcare professional can advise whether it is appropriate for your individual circumstances.

Our Recommendation

At the London Osteoporosis Clinic, we work with trusted partners to identify high-quality vitamin D supplements that meet our standards for quality and reliability.

To learn more about choosing a vitamin D supplement, including one of the products currently recommended by the London Osteoporosis Clinic, please visit our recommended Vitamin D supplement.

A Final Thought

Vitamin D supplements are intended to complement—not replace—a healthy lifestyle.

The best approach to maintaining healthy vitamin D levels combines:

• Sensible sunlight exposure.
• A healthy, balanced diet.
• Regular physical activity.
• Appropriate vitamin D supplementation where needed.
• Blood testing when clinically indicated.

When taken at the recommended dose, vitamin D supplements are safe for most people. However, very high doses should only be taken under the guidance of a healthcare professional.

If you are unsure whether vitamin D supplementation is right for you, or you have osteoporosis or another medical condition affecting bone health, please seek advice from your doctor or healthcare professional.

Next course: Protein — Building Blocks for Bone →

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Written by Dr Taher Mahmud of the London Osteoporosis Clinic.
Provided for education and not a substitute for personalised medical advice.