Meet the Cast
Some of the friendly bacteria which help you most are residents, others are transient visitors, staying in your digestive tract for a few weeks before passing on.

The key players in this drama of life and death, territorial demands and ferocious battles involving villains of great power and heroes with surprising weapon systems, are as follows:¹³

• Lactobacillus acidophilus: This is the main inhabitant of your small intestine in humans and animals. It is also found in the mouth and vagina.

  Acidophilus manufactures lactase to digest milk sugar and produces lactic acid which suppresses undesirable bacteria and yeasts. Some strains produce natural antibiotics. They also lower cholesterol levels and kill Candida yeasts.

  They are very susceptible to poor diet and stress conditions (pollution, antibiotics such as penicillin).

• Lactobacillus bulgaricus: This is a transient but very important bacteria. Together with Streptococcus thermophilus it makes yogurt. Some strains of bulgaricus and thermophilus also produce antibiotics which kill harmful bacteria.

  By manufacturing lactic acid these encourage a good environment for the resident bacteria such as acidophilus and the Bifidobacteria.

• Bifidobacterium bifidum and B.longum: These is a the main inhabitants of your large intestine. Bifidum is also found in the vagina and the lower part of the small intestine.

  In breast-fed infants and adolescents these make up 99% of the entire flora of the bowel. There is strong evidence that the numbers and efficient working of these bacteria decline as we age and with any decline in our health status.

  They produce a number of specialised acids and use these to prevent colonization of the large intestine by invading bacteria, yeasts and some viruses.(see Box)

  They help infants retain nitrogen thus increasing their weight and they prevent potential toxicity from nitrites in your food; manufacture B vitamins for you as well as helping detoxify bile from which they recycle oestrogen in women.

• Bifidobacteria infantis: This is the main inhabitant of every infant’s intestines and is found in small amounts in the vagina. Its functions are very much the same as the other Bifidobacteria.In a freeze-dried form it is the only probiotic product which should be supplemented to infants without professional guidance (see Box)

What Damages the Friendly Bacteria?
Many factors influence just how healthy the flora are. While the type of friendly bacteria living in a region may seem much the same in health and disease, the tasks they perform change according to circumstances.

For example when Bifidobacteria are in a good state of health they will detoxify pollutants and carcinogens as well as manufacturing the various B vitamins as listed above. When in a poor state of health however they just cannot do these jobs as well or at all.

So what makes them function less efficiently?

• The level of local acidity is one major influence and this is affected by your diet and digestive function and most importantly by any stress you are under.¹⁴

• Another important influence is the wave-like contraction of the intestines (called peristalsis) which moves food along the intestines.

  If it is too rapid (as in diarrhoea or irritable bowel syndrome or colitis) this severely reduces the efficiency of the flora.