Fermentation. It's one of the food buzzwords of the last few years. And whenever something's a buzzword I feel the need to approach with caution.GOOD BUGSFermentation. It's one of the food buzzwords of the last few years. And whenever something's a buzzword I feel the need to approach with caution.But fermentation, unlike some other recent trends - foams and savoury sorbets spring to mind - is not some newfangled thing; it's an essential component of our diets.Bottom line: bacteria are our friends. Such close friends, in fact, that many microbiologists say there are many more bacterial cells inside and upon us than there are human cells.Food writer Michael Pollan claims that we might be only 10% human if cell numbers, rather than weight or volume, are what's counted. Every day, it seems, we're discovering just how essential these bacteria are. There's no human culture that doesn't (or didn't) practise food or drink fermentation of some sort.Babies are born with ''sterile" bacteria-free guts which take up to three years to be colonised by the same variety and (relative to body-weight) amount as an adult's gut. Until recently, doctors were puzzled by the presence of oligosaccharides in breast-milk, because infants can't digest such carbohydrates.Now they've realised that these are not there to nourish the infant directly, but to nourish one essential gut bacterium, Bifidobacterium infantis. That's how badly our bodies want us to hold onto bacteria.Until perhaps half a century ago, our diets were rich in bacteria: a loaf of bread, a tub of yoghurt, a helping of sauerkraut, soya sauce or raw milk cheese, all bustled with bacteria. This may still be the case for small rural communities, but most urbanised eaters are living in a terrifyingly sterile food world.All ''commercial" bread has bypassed the proving process and contains no beneficial bacteria at all. So-called yoghurt is not made through lactic-acid fermentation, but is milk sweetened and thickened with gelatine and/or starch and/or fruit puree. Most soya sauce is no longer fermented, so it still contains the toxins which make unfermented soy so bad for us. Sauerkraut is simply soured with pasteurised (dead) vinegar. Processed cheese? Some of it contains only 10% actual cheese, and fermentation is zero.The solution is slightly annoying: make it yourself or change your buying patterns. Real sourdough bread is available, and for fail-safe bacterial happiness, keep some real fermented sauerkraut around. Delicious jars of the stuff are available at Cheese Gourmet on 3rd Avenue in Linden (011-888-5384) along with cultured, wonderfully bacteria-rich stinky cheeses, or at most whole-food shops. Probiotics are a fall-back solution, but good sourdough bread, ripe Brie and a properly brewed beer are surely more satisfying medicines...