1.6 Outline the importance of calcium and vitamin D for bone development

This guide will help you answer 1.6 Outline the importance of calcium and vitamin D for bone development.

Bones form the framework for the human body. They support us, protect organs, and help us move. From birth to old age, bones go through many changes. Two nutrients stand out as being very supportive for bone development: calcium and vitamin D.

What Bones Are Made Of

Bone tissue is made up of a hard outer layer called cortical bone and a spongy inner area known as trabecular bone. Both parts need minerals and proteins to remain healthy. Calcium, a mineral, and vitamin D, which helps the body absorb that mineral, play key roles. Without enough of them, bones can weaken and become prone to fractures.

Calcium

Calcium gives bones strength and structure. About 99% of the calcium in the human body is found in bones and teeth. It acts as a storage bank. The body uses this stored calcium whenever it needs it for other bodily functions.

Key Roles of Calcium in Bone Development

• Supports the growth of strong bones during childhood and adolescence
• Helps maintain bone mass during adulthood
• Reduces bone loss in later life
• Repairs bone after injury or damage

Calcium is involved in other important processes too, including nerve function, muscle contraction, and blood clotting. However, when we do not get enough calcium in the diet, the body will draw on the calcium stored in bones to meet these needs. This can make bones thinner and more fragile over time.

Needs Across the Life Course

• Babies get calcium through breast milk or infant formula.
• Children and teenagers need more calcium than adults because their bones grow quickly.
• Women after menopause often need extra calcium, as bone loss speeds up when oestrogen levels drop.
• Older adults need to continue getting enough calcium to keep their bones strong.

Foods That Contain Calcium

Calcium comes from both animal and plant foods. Examples include:

• Milk, cheese and yoghurt
• Tinned fish with soft bones, like sardines and pilchards
• Green leafy vegetables such as kale and broccoli
• Tofu made with calcium
• Fortified foods, like some plant milks and breakfast cereals

Not all plant-based foods are high in calcium. For example, spinach and rhubarb contain calcium but also have substances called oxalates. Oxalates stop much of the calcium from being absorbed.

Vitamin D

Vitamin D is key because it helps the body absorb calcium from food. Without enough vitamin D, not much calcium enters the bloodstream from the gut, no matter how much is eaten. Vitamin D also makes sure the body keeps proper levels of calcium and phosphate in the blood.

How the Body Gets Vitamin D

• Sunlight: The skin makes vitamin D when exposed to sunlight, mainly in the summer months in the UK.
• Food: Only small amounts naturally occur in foods. Good sources include oily fish (such as salmon and mackerel), egg yolks, liver, and fortified spreads or cereals.
• Supplements: Some groups, such as pregnant women, infants, and older adults, may be advised to take supplements.

In the UK, from October to March, the sun is not strong enough for the skin to make vitamin D. Many people need to rely on food and supplements during these months.

Results of Not Getting Enough Vitamin D

If the body lacks vitamin D:

• Only small amounts of calcium are absorbed from the diet.
• Blood levels of calcium can drop, and bones lose calcium to make up the difference.
• This leads to weak or soft bones.

Children who lack vitamin D may develop rickets. This causes bone pain, poor growth, and deformities like bowed legs or swollen wrists. Adults can develop osteomalacia, which leads to bone pain and muscle weakness.

The Relationship Between Calcium and Vitamin D

Calcium and vitamin D work as a team. Getting plenty of calcium, without enough vitamin D, will not give full protection to bones. The same is true the other way round.

Here’s how they work together:

1. Vitamin D increases the amount of calcium absorbed from food in the gut.
2. The body uses the absorbed calcium to grow and repair bone tissue.
3. If vitamin D is missing, calcium passes through the gut without being absorbed, and the body draws on calcium stored in bones.

Taking high levels of calcium without vitamin D does not prevent bone weakness. Both nutrients need to be balanced for good bone development.

Bone Growth in Childhood and Adolescence

During childhood and teenage years, bones grow fast. Most of the adult skeleton is laid down by the late teenage years. To build strong bones, children and teenagers need plenty of calcium and vitamin D.

Factors that help during this stage include:

• A diet rich in dairy, green vegetables, and other calcium sources
• Regular safe sunlight exposure for vitamin D
• An active lifestyle with weight-bearing exercise (e.g., walking, running)

Bones store up calcium during these years. This sets the foundation for healthy bones in adult life. If not enough calcium is stored, bones can be weaker when older.

Maintaining Bone Health in Adults

Bone tissue is not fixed. It is constantly being broken down and rebuilt in a process called bone remodelling. Adults need to keep up their intake of calcium and vitamin D to:

• Maintain bone mass
• Repair everyday wear and tear
• Replace lost bone tissue

Women, especially after menopause, need to pay attention to calcium and vitamin D. Loss of the hormone oestrogen speeds up bone loss. This increases the risk of osteoporosis, a condition where bones become thin and break easily.

Men can develop osteoporosis too, more often if they have low testosterone or drink too much alcohol.

Risks of Deficiency

Lack of calcium and vitamin D can affect anyone, but some groups are more likely to have low intakes or low blood levels:

• Elderly people who spend little time outside
• People who cover most of their skin for religious or cultural reasons
• People with dark skin, as more melanin in the skin means less vitamin D is made
• Vegans and people who avoid dairy or oily fish
• Babies and children who are only breastfed and whose mothers are low in vitamin D

Long-term deficiency can lead to problems like smaller, weaker bones and more fractures.

How Much Do We Need?

In the UK, government guidelines suggest these daily amounts:

• Calcium: Adults need about 700mg per day. Teenagers need more, up to 1000mg.
• Vitamin D: 10 micrograms (μg) per day for most people aged 4 and over.

Some people need higher amounts, for example, older adults or those who cannot get enough sunlight.

Safe Intake

Getting too much calcium or vitamin D can cause problems. Large doses of calcium from supplements may cause kidney stones or upset stomach. High amounts of vitamin D can increase calcium in the blood to unsafe levels. This can lead to damage to the heart, kidneys, and other organs.

It is rare to get either nutrient from food intake alone. Problems usually happen only if large doses of supplements are taken for a long time.

Supporting Bone Health at Every Age

Bones need support throughout life. Children and young people build bone mass, adults maintain it, and older adults need to prevent loss. Diet, sunlight, and activity are all important.

Awareness of risk factors such as limited sun exposure, food choices, and stage of life can help highlight when more support is needed. Health professionals can advise on diet and supplements when needed.

Terms Explained

Osteoporosis
A disease where bones become thin and break easily.

Rickets
A condition in children where bones become soft and weak, often causing deformities.

Osteomalacia
Softening of the bones in adults, usually due to too little vitamin D.

Bone remodelling
The lifelong process where old bone is removed and new bone is formed.

Micrograms (μg)
A unit of measure for very small amounts, often used for vitamins.
1 microgram (μg) = 0.001 milligrams (mg).

Fortified foods
Foods to which extra nutrients, like vitamin D or calcium, have been added during production.

Tips for Meeting Needs

• Eat a balanced diet with enough calcium-rich foods.
• Spend time outside during daylight, especially from April to September.
• Talk to your GP or a pharmacist if you may be at risk of low vitamin D.
• Follow supplement advice only as recommended.

Final Thoughts

Bones shape our bodies and give us the strength to move, play, and live independently. From early life through old age, calcium and vitamin D remain two nutrients right at the centre of keeping bones strong.

Diet and sunlight give us what we need. For many children, teenagers, and adults, a healthy diet and outdoor activity are enough. People living in the UK, with long winters and little sunlight for much of the year, need to think about how to get vitamin D when the sun is weak. This is even more important for people who get little sunlight for other reasons.

Early years are the best time to build strong bones, but it is never too late to strengthen and protect them. Even adults who did not get enough calcium or vitamin D as children can lower their risk of bone disease by making changes now.

Checking diet and lifestyle, being aware of warning signs, and seeking advice when needed can help everyone reach and keep the best bone health possible. Bone diseases can have a big impact on quality of life, but with good habits and knowledge, their chances can be reduced.

Remember – balance is key. Aim for regular, moderate amounts of both nutrients from a variety of sources. Your bones will thank you for it at every stage of life.