Healthy Bones The Great British Space Dinner Secondary Schools

Why do we have bones? Bones provide support to the body. Bones protect important organs e.g. the heart and lungs. Bones help us with movement (e.g. walking, running). Adults have 206 bones in their body.

Bone formation Bone is a living tissue which means old cells are replaced by new cells throughout our life. Therefore bones are continuously being made and remade. This process helps children to grow and it helps adults to maintain strong bones. Our bones start to form before birth and grow until adulthood. Bones become strongest when we are in our early twenties. From about 40 years of age our bones start to get weaker.

Structure of bones Bones are made from a mix of protein, calcium and phosphorus. Protein (collagen) in the bones works a bit like glue and holds the bone together. Bone tissue is distributed in two forms: –Compact – the outer part of bones – provides strength –Porous – the inside of bones acts as a shock absorber for the sites that are constantly in motion, e.g. limbs or spine Did you know? –If bones were made only of protein they would be soft and if they were made only of minerals they would crumble easily. Image source: NASA

What is peak bone mass? It is important to build strong bones when we are young to prevent them from becoming weak in later life. Peak bone mass is the maximum amount of bone mass acquired during life. Bone growth and calcium deposition in bones is higher during puberty than in any other time in life. Amount of deposition depends on genetic and environmental factors. Some environmental factors such as diet and exercise affect peak bone mass.

Bone health on Earth For strong healthy bones we need certain nutrients from our food along with sunlight and regular exercise. Calcium - 99% of calcium in our body is found in bones and teeth. 1% is found in soft tissues and body fluids. We need adequate amounts of calcium from our diet for strong, healthy bones, Vitamin D – sunlight during summer months produces vitamin D under the skin, which helps absorb dietary calcium to make strong bones. For most people, sunlight provides about 90% of their vitamin D and diet only 10%. Regular exercise, particularly weight- bearing exercise is important for strong, healthy bones.

Bone health in space Earth keeps us from floating away because of its gravity. Astronauts in space are effectively in ‘free-fall’ around the earth – so they feel like they are in zero gravity. Since the ISS is also in free-fall, astronauts seem to float in space. We use our bones and muscles to resist the pull of gravity, but as astronauts float in space their bones and muscles do not have to work so hard. This leads to loss of bone and muscle, which can make astronauts weak. To keep bones and muscles strong in space, astronauts eat a healthy diet and exercise for at least 2 hours each day. Image source : NASA

Food sources of calcium Calcium is essential for bones to grow and be strong. Can you name any sources of calcium? Foods that provide calcium are: –Dairy products (e.g. milk, yogurt and cheese) –Bread (as it is fortified in the UK) –Soya beans –Tofu –Edible soft bones found in canned fish –Green leafy vegetables, like broccoli and spring greens. Research which foods contain the most calcium and which foods contain the least.

Recommended Intake for Calcium The recommended intake for young people aged years is 800mg per day and 1000mg per day for boys. This can be provided by 2-3 servings of milk and dairy foods everyday, such as: –a 200ml glass of milk –a small (150g) pot of yogurt –a matchbox size (30g) serving of cheese Did you know? –Semi-skimmed and skimmed dairy products contain as much calcium as full fat versions.

Sources of Vitamin D The major source of vitamin D for most people is sunlight during the summer months. Few food sources contain large amounts of vitamin D. Small amounts of vitamin D can be obtained from: –oily fish –meat –eggs –fortified breakfast cereals –margarine/spreads

Vitamin D and calcium in space Astronauts in space need 1500mg of calcium each day to keep their bones healthy. This is higher than the requirement on Earth because long duration flights can cause bone losses of up to 2% per month. What foods could astronauts take to space to make sure they have an adequate calcium intake? –Cheese, milk, yogurt, leafy green vegetables, soya, tofu, edible bones in fish. How would they need to be processed to take to space? –Heat processed, canned or dehydrated. Why are vitamin D levels a problem in space? –The ISS shields astronauts from the sun’s rays. This means astronauts cannot make vitamin D from sunlight, so astronauts on the ISS take a vitamin D supplement.

Bone strengthening exercises Weight-bearing exercise and resistance exercise are particularly important in improving bone density. Weight-bearing exercises are exercises where your feet and legs support your weight. This includes brisk walking, running, dancing, climbing stairs, basketball, badminton, volleyball and rope skipping. Resistance exercises use muscle strength, where the action of the tendons pulling on the bones boosts bone strength. Resistance exercise includes press-ups, weightlifting or using weight equipment at the gym.

How do astronauts exercise in space? The ISS has its own gym which contains special exercise equipment to allow astronauts to exercise. The ISS contains a stationary bicycle, a treadmill and an advanced resistive exercise device (ARED). Equipment is specially adapted to hold the astronauts onto the bicycle or on the treadmill. The treadmill allows astronauts to run in space – a weight-bearing activity. –Click here to watch NASA astronaut Karen demonstrate the ISS treadmill.here The advanced resistance device allows astronauts to carry out resistance exercise in space. –Click here to watch NASA astronaut Mike demonstrate the ARED.here Image source: NASA

Why are strong bones important? Excessive loss of bone tissue is called as osteoporosis. This leads to increased risk of fracture due to fragile bones. Space research projects are investigating bone loss occurring in crewmembers which is similar to osteoporosis on Earth. This could help with preventative methods and rehabilitation for patients on Earth who have similar bone conditions. A normal and an osteoporotic bone Can you spot the difference?

Summary Healthy bones are important on Earth and in space. Bones provide support, protect important organs and are help us carry out movement such as jumping and running. On Earth and in space we need a healthy diet and regular exercise to keep our bones healthy. Image source: NASA

This presentation has been developed in collaboration with the British Nutrition Foundation. For further information and resources, go to: