Investing in bone health
Wing-kei asks: Which foods are rich in calcium and good for bone growth?
Wynnie says: Bone is a living tissue, which means it's continuously being remodelled - that is, old bones are broken down and replaced by new ones.
The formation of bone and replacement of old bone tissue takes place throughout life.
But from the age of around 30, more bone is lost than can be replaced, which results in a decrease in bone strength.
During adolescence, the skeleton is actively growing and getting bigger and stronger. By the end of your teens, bone growth has already been completed.
This is when bone has achieved its 'peak bone mass', the stage when your bones are at their strongest. The higher the peak bone mass, the greater protection your skeleton will have against bone loss and osteoporosis (brittle bone disease) later in life.
Peak bone mass is influenced by genetics and whether you're male or female. It can be increased by ensuring your diet contains enough calcium and vitamin D from childhood to early adulthood, and by doing regular weight-bearing exercises.
So invest in your bone health right now. Think of your skeleton as a savings account - but you can only deposit calcium into your bone bank from childhood to young adulthood.
Eat your way to healthy bones by including dairy foods such as milk, yoghurt and cheese - these foods are rich sources of calcium.
Other good sources are calcium-fortified breakfast cereals and soy milk, pulses, tofu, nuts, dried fruit, green leafy vegetables such as kale, pak choi, mustard greens, and fish such as salmon or canned sardines.
Teens should include three to four servings of calcium-rich foods in their daily diet - for example, a couple of glasses of low-fat milk, a tub of yoghurt and a bowl of fortified breakfast cereal.
Your body uses calcium best when it's spread throughout the day, so include a calcium-rich food at each meal or snack time.
Vitamin D helps your body to absorb and use the calcium it needs. This fat-soluble vitamin can be synthesised via the action of sunlight on your skin. You'll need to be out in the sun for about 15 to 20 minutes to get enough.
If you're not a sun worshipper, the best food sources of vitamin D are fortified dairy products and oily fish such as salmon, tuna, and mackerel.
Weight-bearing exercises build denser and stronger bones, particularly when the bones are still growing.
This is why it's so important to be physically active every day.
The best exercises for building up the skeleton include jumping, side lunges, skipping, weight-lifting, jogging, hiking, stair-climbing, step aerobics, dancing, tennis, badminton, squash and other exercises that require your muscles to work against gravity.
Wynnie Chan is a British-trained nutritionist. If you've got a question for her or would like to be featured in this column, e-mail firstname.lastname@example.org