As with most people approaching 40, we've started to notice a few extra laughter lines and wrinkles. But to be honest, it's not these external signs of ageing that worry us most. Let's be serious, no one ever died from having too many wrinkles. What all of us are interested in is staying young on the inside. It's the state of our bones, heart, lungs, blood vessels, liver and, heaven forbid, our brain that has us thinking.

Luckily for us, most of our cells are being constantly replaced, new for old. For example, the cells in our gut lining are replaced every three days, our skin every 28 days, our live cells every six weeks, even our bones are constantly changing their cellular structure. Indeed, there is very little in our bodies that is more than 10 years old. So, why is it that we don't all look like fresh-faced youngsters?

The reason we age is partly due to genetics, and largely to do with our lifestyles and environment. On the genetic front, every time our cells divide to make new ones, our DNA must replicate itself to make a perfect copy. This process goes off without a hitch almost 100 percent of the time but, occasionally, a mistake is made in the genetic code. If the damage is not fixed, the error is passed on to future generations of cells, which are less than perfect, and we slowly age.

We are also constantly bombarded with toxins, UV rays from the sun, bacteria, viruses, stress hormones, free radicals and smoke, all of which can cause wear and tear and DNA damage. However, what is now clearer than ever is that eating healthy foods, exercising regularly, relaxing, having a laugh, not smoking and even flossing your teeth daily are some of the most powerful anti-ageing tools we have.

1) Thoroughly Floss Our Teeth Every Day

Flossing our teeth every day may reduce our chances of heart attack, stroke and accelerate ageing. This is because without flossing, we are more likely to develop chronic gum disease. Certain bacteria, inflammatory and toxic substances may enter the bloodstream and trigger plaque formation in the arteries. It is these plaques that cause the problems.

2) Take Time Out to Relax

There is no doubt about it, too much stress can cause premature ageing. Going too fast may accelerate the wear and tear on our body, and  can lead to lifestyle of too much coffee, alcohol and fast food, and too little exercise and relaxation. About one third of people in the workplace are apparently sleep deprived, so get more sleep by going to bed earlier.

Relax regularly by doing something enjoyable. A feel-good fix with yoga, tai chi, meditation and exercise can help lower the levels of damaging, stress hormones. It can also help to lower the blood pressure, improve sleep and diet and keep our relationships more harmonious.

Enjoying life and having a sense of humour are often trademarks of those people who are more than 100 years old. Common traits among centenarians include a positive outlook and a sense of humour. They also refuse to see age as any sort of limitation on their enjoyment of life. 

3) Eat Plenty of Fruit and Vegetables

Everyone knows that a diet of salty, fatty, high-kilojoule foods often leads to trouble. Heart disease, stroke and even impotence can all be the consequences of unhealthy diet. Cancers, such as breast and prostate, may also be linked to what we eat.

The good news is that fresh fruit and vegetables are rich in anti-oxidants, which neutralise the effect of damaging free radicals in our bodies. Free radicals are generated as toxic by-products of our metabolism. So aim to eat at least five to seven serves of fruit and vegetables a day, and try to limit the intake of full-fat milk and cheeses, cream, chicken skin, butter, fast foods, takeaway, pastries, cakes and biscuits.

4) Maintain A Healthy Body Weight

It's impossible that a reduced kilojoule intake may be associated with reduced cancer risk and a longer life span. In the laboratory, animals such as mice and rats, are known to live around 30 percent longer if they are fed a very low-kilojoule diet. The theory is that eating less exposes us to less harmful free radicals, which means less damage to cells and DNA.

However, before we cut back too drastically on our food intake, keep in mind that eating fewer kilojoules may make it harder to eat enough of the right nutrients.

5) Challenge Ourselves With Mental Exercises

Keeping our mind active with challenges keeps our brain young. The brain is a bit like a muscle - it's a matter of "use it or lose it". So by studying, reading, doing the crosswords, learning a new skill or language, playing a musical instrument or doing volunteer work, we can keep our brain cells more youthful. It is believed that active brains create more networks between neurons, and this builds up the brain's reserve. 
This way the brain is more protected against deterioration with age. For some people, keeping mentally active may reduce the risks of dementia. 

6) Stay Physically Active

Exercising and a little strength training can protect our heart and bones, and help to lift mood and ward off depression. It can improve memory and sleep, and may even reduce the odds of developing breast or colon cancer. A trim, fitter body also helps us feel and look years younger. 
Many people, as they age, start to have more fat and less muscle, leading to a slower metabolism, less strength and more injuries such as bone fractures. Strength training is one way to slow down the body clock, as it increases muscle mass and energy levels.

7) Avoid Cigarette Smoke

It's well documented that cigarette smoke contains toxins that may damage DNA. This can lead to cancer, heart disease and accelerated ageing of our internal organs and skin. It can also fast track our diseases associated with ageing - even more reasons to quit smoking or avoid passive smoking.

8) Eat Calcium-Rich Foods
Eating at least three serves of calcium-rich food a day, and doing daily weight-bearing exercises, such as walking, helps to build and maintain healthy bone thinning or osteoporosis. One serve of calcium is equivalent to a glass of low-fat milk or soya milk, or a 200g tub of yoghurt.

9) Stay In Touch With Family and Friends

Visit and phone our families and friends regularly. The closeness of an extended family and other relationships is often a feature of those who live long, healthy lives.