In many ways it is true ? you are what you eat! Most cells in your body are replaced within six months and the process of replacing and building new cells depends on the nutrients available. Therefore, the healthier your diet, the healthier you become ? quite literally. However, it is sometimes more complicated than this because not only are you what you eat, but more specifically, what you can digest and absorb.

Now, your digestive tract is amazing! Did you know that it is approximately 30 feet long and that it has a surface area the size of a small football pitch? Most cells lining it will be renewed every four days and over your lifetime, approximately 100 tons of food will pass along it. You are also host to about 100 trillion bacteria (give or take a few) and it's here that we find some friends in unexpected places!

We all have some good, and some bad, bacteria in our digestive tracts. Recently, these have become widely referred to as "friendly" or "unfriendly" bacteria. All of us have some unfriendly bacteria, but so long as we have plenty of friendly bacteria, the bad guys are kept in check. Two of the most common and important friendly bacteria are L. acidophilus and B. bacterium.

Here are just some of the things that friendly bacteria do:

They make certain nutrients (B vitamins, Biotin, A and K) in the colon which are then absorbed into the bloodstream and distributed to cells in the body. They also aid the absorption of calcium and other minerals

They help digest your food

They are responsible for 60 percent of your immunity, helping to fight infections. Several studies show that they halve recovery time from food poisoning or travellers diarrhoea

They promote the health of, and repair, the digestive tract

They can help to reduce inflammation so may be beneficial to those with inflammatory conditions such as rheumatoid arthritis, irritable bowel and eczema.

But how friendly are your bacteria? Common symptoms of too few friendly bacteria, and too many unfriendly bacteria are: bloating, gas, burping, fatigue, frequent infections, thrush, candidiasis, constipation, diarrhoea and anal itching. If any of these symptoms sound familiar, then consider this ? antibiotics, the birth control pill, stress, high sugar intake, high alcohol intake, spicy food, parasitic infections and bouts of food poisoning all deplete friendly bacteria and encourage an overgrowth of unfriendly bacteria.

The good news is that live natural yoghurt and cottage cheese are two excellent dietary sources of friendly bacteria. Unfortunately many of the fruity live yoghurts in the supermarkets, may also contain lots of sugar (up to four teaspoons per serving!) In this instance, it is better to eat plain live yoghurt and add a little fresh fruit for sweetness. Fruit and vegetables (especially bananas, onions and Jerusalem artichokes), soya and parsley are also worth including in your diet as they are rich in something called FOS which helps friendly bacteria to replicate in your digestive tract. Additionally, you can buy supplements of friendly bacteria ? this is often a wise choice after a course of antibiotics or if you are fighting a yeast infection. If you choose to do so, ask for a top quality brand from a good health food store (such as Down to Earth or Rock On) and look for one that contains at least 100 million viable organisms; it's also beneficial if the supplement contains FOS. If you are allergic or intolerant to dairy, ask for friendly bacteria that come from a non-dairy source.

Whilst nurturing your friendly bacteria is important for digestive health, there are several other steps you can take to improve digestion and optimise the absorption of nutrients from your diet:

1. Eat at least one serving of RAW fruit or vegetables daily. These raw foods contain natural enzymes that help you to break down and absorb your food efficiently.

2. If you suffer from persistent indigestion, limit your fluid intake at mealtimes to one small glass of water. Too much water close to meals can dilute digestive enzymes. Most adults need approximately two litres of water daily, but try to drink this in between meals.

3. Always chew your food THOROUGHLY before swallowing. Good digestion begins in the mouth.

4. RELAX! Try and relax when you eat. Stress causes digestion to seize up.

5. Reduce wheat products. Wheat is often irritating to the digestive tract and causes many people bloating and abdominal discomfort in large amounts. Try incorporating wheat-free cereals/pasta/bread, Ryvita and oats into your diet in place of some of the wheat. Some people are particularly sensitive to wheat and have wheat intolerance. However, consult your GP, nutritionist or dietician before eliminating a food group from your diet. They will need to make sure you are still receiving a balanced intake of nutrients.

6. Consider supplementing friendly bacteria if relevant for you.

7. Ensure adequate fibre intake. Fibre is found in fruit, vegetables, whole grains, nuts and seeds and has wide ranging health benefits ? more on this next week!

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