Did you know the UK had just 2.3 hours of sun per day on average in January 2024?¹ Ever thought about how little exposure to sunlight can impact your child's bone health? 

We're here to guide you and give you the information you need to keep your kids' bones strong and healthy.

Introduction

The teenage years are an important time for strong bones that can support throughout life. Eating a balanced diet and getting enough vitamin D from sun exposure or supplements help adolescents grow dense and sturdy bones. A high amount of physical activity time also contributes to bone strength during this crucial growth phase. By focusing on the tips provided below, we can help young people develop strong bones and beneficial mindsets throughout their lives.

Why is bone health important?

Do you know that 90% of peak bone mass is developed by the age of 18 in those assigned female at birth and 20 in those assigned male at birth,² with additional gains of 5% to 10% during young adulthood?³ It means that during childhood and adolescence, most of our bones have reached their maximum strength and size. 

Specialists refer to this period as a “Bone Bank” and youth is the best time to “invest” in healthy bones. An early deposit serves as the foundation for bone health. Later on, if withdrawals exceed deposits, bone integrity will be compromised leading to to situations where you are prone to fractures or even osteoporosis. 

What do our bones do?

Our bones are made of proteins collagen, and minerals, mainly calcium. and it has many important functions in the body:⁴

• Bones joined with muscles hold up the body when standing and moving
• The skeleton provides a strong framework to support and protect the organs in our body from injury
• Bones house the bone marrow, which is responsible for making blood cells and platelets
• Bones store growth factors and minerals, such as calcium
• Bones release factors into the blood that help organs function properly 

How do our bones grow and develop?

During infant development and childhood growth, our skeleton goes through continuous change. This involves the removal of old bones and the formation of new bones. This process helps maintain mineral levels, repairs damaged bones and adapts to changing skeletal stresses. During the first three decades of life, the skeleton does its best job growing both in size and density until around 30, when your bone mass is accumulated to its maximum.⁵

Our genes account for 60-80% of our skeleton's potential size and strength.⁵ Although genetics play a major role, the fact that many adolescents still do not reach their full "bone bank" potential. Research showed that 16-year-old teenagers in 2017-2018 had a lower bone density around 10% less in people assigned male at birth and 11% less in people assigned female at birth compared to their equivalent between 1979 and 1981. This lower bone mass in today's children also raises concerns about a higher risk of developing osteoporosis and fragility fractures later in life.⁶ Given these worries, it is crucial to understand how to promote healthy bone development.

What affects bone health?

Peak bone mass is considered a significant predictor of future osteoporosis and fracture risk. Therefore, it is important to maximise your child’s genetic potential for reaching their peak bone mass. Research has estimated that a 10% increase in peak bone mass would delay the development of osteoporosis by 13 years and reduce fracture risk from osteoporosis by up to 50% in post-menopause women.⁶

genetic factors might give you an upper hand when growing up compared to your counterparts in other population groups. For example, individuals of African descent have higher bone density than white people, while Caucasian people have higher bone density than Asians or Hispanics.⁵

However, having higher bone density is not directly associated with a lower risk of fracture as other factors should be taken into consideration, such as bone structure, muscle strength, and body fat levels.⁷ Apart from the genetic influences, to optimise your bone health, environmental, dietary, hormonal, and other risk factors are all important.⁵

How to keep your bones healthy?

Many factors that can affect bone health:

• Calcium
• Vitamin D
• Physical activity

Calcium

Calcium plays a key role in bone health at all ages. Calcium demands are particularly high during the rapid period of growth in teenagers, and at older age, when the body’s ability to absorb calcium declines. 

Our skeleton contains approximately 98% of the calcium in the body.⁸ Calcium is a mineral which cannot be produced by our bodies. We rely on our food and/or drink for intake. Low levels of calcium can increase the likelihood of bone breakage, loss of teeth, brittle nails, muscle spasms, and slow development in children. 

Dairy food, such as milk, yoghurt, and cheese, are the most abundant sources of calcium in the diet and they also contain other growth-promoting elements. A UK study shows that healthy secondary school girls who had additional milk consumption, roughly an extra 300 mL, experienced better bone mineral acquisition and a significant increase in growth hormone.⁹ Additional food sources of calcium include certain green leafy vegetables (e.g., broccoli, curly kale, and spinach), whole canned fish such as sardines and pilchards, nuts, and tofu.¹⁰

Dietary recommendations for calcium intake vary from country to country. However, there’s a universal alarm that many children do not take in enough calcium for optimal bone health.¹¹ 

Association of UK Dietitians provides guidance on how much calcium is recommended for children and adolescents attached below. What exactly consider a very low intake risking fractures during childhood is uncertain, but children with calcium intakes < 300-400 mg per day have higher risk of developing rickets. 

Rickets is a condition that affects bone development in children with unpleasant bone pain, poor growth and weak bones. It was common in the past. the NHS suggests that there has been an increase in cases of rickets in recent years as more children have insufficient calcium and vitamin D intake. This trend may be partly related to the fact that many young people do not have a proper breakfast, with its traditional variety of calcium-rich foods, such as milk.¹¹ Moreover, milk consumption has been highly displaced by increased consumption of sodas and sweetened drinks.¹¹ Table 1 shows the daily recommended amounts of calcium for different age groups.

Table 1: Daily recommended amounts of calcium for different age ranges

In some cases, milk as a source of calcium is not considered by vegans and lactose intolerants. The Association of UK Dietitians also provides a comprehensive guide for a wide range of calcium-rich food and how much they provide per serving as seen in table 2. 

Table 2: dairy and non dairy sources of calcium

Vitamin D

Did you know that vitamin D serves as a big help in absorbing calcium? Without sufficient vitamin D, the body struggles to absorb enough calcium from the diet, even if the dietary calcium intake is high. Vitamin D deficiency can lead to possible health problems in children including rickets, slow growth, and muscle weakness.¹²

children and adolescents at higher risk of vitamin D deficiency include ones with:¹²

• calcium insufficient diets
• limited sun exposure
• very little time outdoors
• those who have dark skin may not get enough vitamin D from sunlight

Low levels of vitamin D are common in the UK as sun exposure is one of the most direct ways to absorb vitamin D. Unfortunately, the UK does not experience much sunlight between October and March. Hence, here are some foods rich in vitamin D that could guide you through the autumn and winter:

• Oily fish such as sardines, pilchards and mackerel
• Eggs, meat, and milk (in small and varying amounts)
• Margarine, and certain types of cereal, that are fortified with vitamin D

However, it is difficult for people to get enough vitamin D from food alone as there are only a few that are good sources of vitamin D. The NHS suggests that children from the age of 4 years to adults need 10 micrograms of vitamin D a day, especially during autumn and winter.

Between March and September, most people can get their vitamin D through direct sunlight on their skin and a balanced diet. However, always make sure to use sun protection to minimise skin damage during long sun exposure time.

Physical activity

Did you know that experts have confirmed that adolescents with high sedentary behaviour are associated with lower bone mineral density than those with low sedentary behaviour? This includes high screen time on television and other technology devices.¹³

Studies have shown that physical activity during adolescence affects bone strength.¹⁴ Additionally, regular physical activity improves body composition, and cardiorespiratory fitness, and overall bone health.¹⁴ Weekly PE at school is beneficial, but not enough. ​​

WHO recommends that children aged 5-17 should:

• Do an average of 60 minutes per day of moderate-to-vigorous intensity activities, such as brisk walking, and cleaning (for example: washing windows, vacuuming, and mopping)
• Do vigorous-intensity activities at least 3 days a week, such as fast bicycling, and playing football
• Avoid a sedentary lifestyle, particularly spending too much screen time

Other beneficial factors

Other factors that could also benefit your children’s bone health include, vitamin K and protein, both of which help strengthen our bones.

Moreover, girls begin puberty approximately at the age of 10 and start having menstrual periods at about the age of 12. Regular periods are important to female bone health because it indicates that our body is producing sufficient oestrogen (a hormone that also improves calcium absorption in our body). 

Avoid risk factors

In addition to poor nutrition and low levels of physical activity, certain lifestyle factors can pose a danger to young bone health. Studies estimate that a third of children will experience a fracture before adulthood.^5,15 Some Common risk factors that can have a significant impact on bone strength are:⁵

• Smoking
• Alcohol
• Coffee
• Soft drinks
• Obesity

Summary

Childhood and adolescence are a very important time for the formation of the skeleton. Bone-healthy nutrition and regular physical activity are the key ways to maximise a child’s genetic potential for strong bones and to set a good foundation for future bone health. 

If you suspect slow development in your kids or facing difficulties in maintaining a balanced diet for your kids, consult your doctor and/or dietitian about a health check and establish a healthy eating pattern for future development.