For active women, coaches, trainers and teachers

Advice on bone health

Sport and exercise are an important part of life for many New Zealand women. For some, sport is an end to itself: to be the best in their field. For others, sport and exercise is a social activity, which helps them to stay healthy and keep in shape. As a result, high demands are made on the body.

Everyone wants to succeed at his or her sport or in achieving fitness goals. But you must ensure you aren't endangering your present or future health in the process. You must strike the right balance between your goals now and your health in the years to come. This article aims to help you achieve this balance - especially when it comes to keeping your bones strong. With the advice given, you can ensure your future health, without jeopardising your immediate health or sport achievement goals.

The structure of bones

A normal healthy bone is as strong and as well engineered as a piece of steel, able to cope with the many stresses and challenges we put on it. But, unlike steel, bone has a web-like structure. This structure makes the bone light, yet strong.

It also allows the bone to act as a shock absorber. Bone is a living tissue. As with the rest of your body, it is continually being remodelled and rebuilt. 90% of your bone mass forms before you are 20 years old. Even until the age of about 30, bone increases in mass and density, as calcium and other minerals are deposited, building up a strong web structure. But as you grow older, your body can start taking calcium from your bones. This causes then to become brittle and prone to breaking.

To ensure that bone continues to develop normally, we need to provide the right balance between exercise, nutrition and hormone levels. Too much exercise and too little food can seriously damage your bones. It can lead to osteoporosis.

After your bones reach their peak bone mass, they will normally maintain this level until your 40's. At this point, your bones start to lose more calcium than is being replaced. When menopause occurs and women stop menstruating, oestrogen levels decline and calcium is lost even more quickly. It is important you have reached and maintained as high a level of bone mass as possible to avoid the serious problems of osteoporosis later in life.

Osteoporosis means 'porous (thin) bones'. The hard outer shell of the bone thins out and the web-like structure becomes less dense. Although the bones stay the same size, their internal structure becomes much weaker. This process also means bones are more likely to break as they age. It is estimated one in three women over the age of 60 in New Zealand will break a bone because of osteoporosis - most commonly the hip, wrists or spine. These breaks are extremely painful and often lead to permanent disability.

Osteoporosis can and does occur in young women in their 20s and 30s, especially if they are under-weight with low body fat, have stopped menstruating or over-exercise. Osteoporosis can often be present without any symptoms.

Surely, being very fit is good for your bones?

Certainly weight-bearing exercise will help develop strong bones in the lower body. For upper body strength additional weight-resistance and weight training exercise is required. So as an active woman you are more likely to have stronger bones then those who sit around all day!

There has to be a good balance. Very intensive training may actually damage your bones. If the amount of training you do reduces your body weight and your body fat to very low levels, you could be at risk. As a woman, your level of body fat should not drop below 18%.

Not eating adequate amounts of food - the calories required to supply your height energy needs, and the minerals required to renew your tissues - will disrupt your hormonal balance and can cause long term problems.

Even if your exercise levels are more moderate, it is absolutely essential to provide your body with the right 'fuel' - both energy and essential vitamins and minerals.

Why are regular periods so important?

Oestrogen is the number one hormone maintaining your healthy bone mass. It is also important for your heart, skin and hair. It you miss your period for 6 months or more, it's a warning sign that your body is low on oestrogen. Oestrogen levels will fall naturally during menopause, but you may also develop low oestrogen if you are underweight or training too much.

If you have already started experiencing problems with your periods you run the risk of bone ageing similar to that of women in their 50s, 60s and 70s. In many cases it can be treated, and if treated early enough, this process may be reversed, but if it is left too late you may face a life marred by fracture, pain and deformity.

At first, stopping periods may even seem convenient, but it's a very important warning sign that all is not well. If your periods become irregular or stop altogether and you are training or exercising intensively, talk with your doctor.

But I need to be slim to meet my goals

While there are many sports and performing arts in which being slim is an advantage, you can't afford to endanger your future health in pursuit of today's goals. Being slim may not be the most balanced lifestyle for you, especially if you are not eating an adequate level of calories and your periods have become irregular. It can even lead to eating disorders such as bulimia and anorexia nervosa.

Recently, doctors have begun to notice that people with current or past eating disorders fracture their bones more than would be expected for their age. These fractures were, in many cases, being caused by low bone density.

If I am to achieve my goals, I cannot afford to put on weight

There are many factors involved in success other than weight; natural ability, correct training, mental preparation, fitness, strength and so on. Remember that your body is ruthless when it comes to meeting its energy demands. If your calorie intake and fat reserves are too low, your body will start absorbing your muscle cells for energy - this will reduce your strength and your performance will definitely suffer.

By changing your lifestyle you can affect your performance for the better. Your bones and your muscle strength will increase. You will feel less tired, you will have better control and you will have much less risk of injury.

My busy life makes it hard to train, compete and eat big meals

Meals do not have to be big, but balanced. You need carbohydrates, proteins, fats, minerals and vitamins every day - but it isn't that hard. Remember to feed those bones by eating a calcium-rich diet - at least 1000mg a day is recommended (for a guide to what this means in terms of food, see the chart below). In return, your bones will cope with the demands you will put on them with less risk of injury.

Remember, smoking, heavy drinking and lots of coffee can depress bone building. By eating properly, you will have more energy. You will also be automatically strengthening your bones for the future. Chocolate and cola may seem an easy option, but you can eat cheaply, conveniently and healthily without disrupting your lifestyle. It just takes a little thought and planning.

Where do I get my calcium?

You may find you don't have nearly as much milk or dairy products in your diet as you did when you were very young. But milk isn't just for children! It's a valuable source of a range of nutrients, especially calcium.

In fact, most dairy products - including cheese, yoghurt, ice cream and milk - provide the great majority of the calcium in the average New Zealand diet. Fat reduced milks (which are also higher in calcium content) are ideal when body weight is an issue.

Contribution of different foods to your calcium intake

• dairy products 56%
• bread and baked goods 12%
• fruit and veges 10%
• meat and alternatives 7%
• cereals and grains 5%
• other 10%.

What if I don't eat dairy products?

All dairy products are valuable in a well balanced diet. But if you don't or can't eat dairy products, it is possible to get enough calcium from other foods. It just takes a little more thought and planning. Fish eaten with bones, tofu, soymilk, some dried beans and nuts contain good amounts of calcium.

Check the chart for more details. If there is not enough calcium in your diet, take advice on whether or not to take calcium supplements.

You're recommended calcium intake and the best places to find it

Amount of calcium needed per day

• women - 4 servings a day
• very active women - 5 servings a day.

Calcium content of common food per serving
(Each serving = approximately 200mg of calcium)

A final word for coaches and teachers

Everyone needs support to develop their self-esteem and to take a personal responsibility for their own health. Training and performance programmes require awareness of individual physiques and nutrient requirements.

Training programmes designed for men may not be appropriate for women as body structure and body chemistry are different. While the shape and size of the human body is relevant in all areas of sport and dance, ultimately success depends on a supremely healthy skeleton supporting that body.

Vigilance is needed in spotting signs of anorexia, fatigue, an undue number of stress injuries, severe weight loss and continuous long spells without periods to ensure that those who may be putting their bone health at risk can be given appropriate advise and treatment. Care should also be taken to avoid doing 'too much too soon' after an injury lay-off, as bone takes more time than soft tissue to heal properly.

Original material supplied by Arthritis New Zealand. Reviewed by everybody.