As functional foods go, that is, foods which claim to be good for you and not just nutritious, probiotics are generating a lot of buzz.
Probiotics are cultures of beneficial bacteria that are normally present in a healthy digestive tract, for instance, the bacteria which turn milk into yogurt.
It may come as a surprise but all of us carry nearly 1.5kg of bacteria in our bodies. We house billions of bacteria from at least 500 different species in our gut and they play many complex roles from regulating immunity to helping with the absorption of nutrients.
Among these are the good bacteria, harmless bacteria and ugly bacteria that can produce powerful toxins and carcinogens.
The gut can be thought of as a battleground between good and bad bacteria. The more the good bacteria colonise the gut, the less space there is for the bad.
This has been recognised for centuries though it was studied scientifically only about a century ago. A Russian microbiologist called Eli Metchnikoff observed that Bulgarian peasants who drank sour milk lived very long and healthy lives. He also found that fermented milk could inhibit the growth of harmful bacteria in the gut, for which he won the Nobel Prize in 1904.
But the promise of probiotics was forgotten when Sir Alexander Fleming discovered penicillin in 1929, leading to the antibiotic era.
Getting your dose
In recent times though, the role of probiotics in health has become the focus of a number of studies. Clinical evidence is mounting for specific strains of bacteria and their therapeutic effects.
Scientists have found that these gut-dwelling bacteria get depleted by disease, stress, poor diet, or medications like antibiotics.
Replacing them through diet or supplementation may help with a range of health issues - from gastrointestinal problems to repetitive yeast or urinary tract infections.
Some strains beneficial to humans have been identified, but a lot more research needs to be done before they can be targeted for specific therapies.
For a commercial probiotic product to be effective, it must contain hundreds of billions of live bacteria that can survive the journey down the gastrointestinal tract into the colon, where they are exposed to strong acids and enzymes.
While not all the products currently available can achieve this, some have special delivery mechanisms such as microencapsulation to ensure that the bacteria do get to their destination.
Mind Your Body gives you a brief guide to the terminology:
PROBIOTICS: Derived from the Greek phrase 'for life', it is defined by the World Health Organisation as 'live microorganisms which, when administered in adequate amounts, confer a health benefit on the host'.
These are available in fermented milks such as Vitagen and Yakult, or yogurt with live and active cultures, and also in powder or pill form in pharmacies.
PREBIOTICS: These are non-digestible components in carbohydrates that help feed specific good bacteria. For instance, a sugar-like substance called fructo-oligo-saccharide (FOS), present in bananas, can help support the growth of good bacteria. Common sources of prebiotics include raw oats, onions, unrefined wheat, barley and soybeans.
SYNBIOTICS: This refers to a product which combines both prebiotics and probiotics in such a way that the former promotes the growth of the latter.
For example, a yogurt with added FOS is a synbiotic.
