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Till then, eat dahi

When I wrote about sourdough bread here a few weeks ago, responses varied.

There was one kind of response, however, that I found particularly intriguing. Why had I not written that sourdough bread was healthier than other bread? Why, asked some readers, had I not mentioned that sourdough was full of bacteria that was beneficial to our bodies?


Well, umm.


   The primary difference between traditional sourdough and most modern white bread, I had written, was that sourdough depended on natural bacteria, both in a starter culture and from the air. Most shop-bought white bread, on the other hand, used commercial yeasts.


   It is easy to confuse yeasts with bacteria, especially when we are discussing their role in cooking. Yeasts are fungi (as are mushrooms, truffles and mould – so it is a vast category) and are normally classed with the vegetable kingdom. Bacteria are not plants. They are living organisms that can be found almost everywhere on earth.


   When foods alter their form and flavour, it is often a consequence of the action of both bacteria and yeasts. In sourdough, though the starter culture is usually bacterial in composition, wild yeasts from the atmosphere will also be attracted to the dough. The final product will have both yeasts and bacteria.


   Cheese was once thought of as being created solely by mould and fungi, but we know now that bacteria have a huge part to play in giving cheeses their distinctive flavour.


   But does the fact that a food has been bacterially-fermented mean that it is good for you?


   Far from it.


   Let’s be clear. All bacteria are not wonderful. There are many harmful bacteria. Most diseases are caused by bacteria.


   In food terms, when something spoils, the chances are that the growth of bacteria has spoiled it. Salmonella is a kind of bacterium that can cause food poisoning. One reason why health authorities in so many countries ask that you cook eggs thoroughly is because chickens may carry salmonella, which can contaminate their eggs and poison us. In fact, one type of salmonella can cause typhoid.


   So the desire to romanticise all bacteria as our wonderful little friends is silly. On the other hand, it is true that our bodies sometimes seem no more than travelling cases for trillions of bacteria. According to one estimate, there are nine bacteria in the body for every human cell.


   What exactly these bacteria do is the subject of much scientific interest. We know that bacteria can help in the digestive process. Billions of bacteria live in our gut and help our systems process the food we eat.


   At some level, most cultures have always guessed that there are benefits from good bacteria, especially when it comes to digestion even if they have not understood the science. That’s why Germans eat sauerkraut and Koreans eat kimchi, both heavily fermented products.


"But do all bacteria help in digestion? And even if you are sticking to so-called good bacteria, how much do you need to consume for there to be a beneficial effect?"

   The South of India is rich in foods that use bacterial fermentation. For instance, when we say that the dosa batter has to be fermented, what we mean is that we must give bacteria the time they need to grow in the dough. A variety of bacteria (and natural yeasts), many of them drawn from the atmosphere, contribute to giving the batter its flavour. The most important bacterium used to ferment the batter is lactobacillus, but other bacteria and wild yeasts also play a role.


   The most significant source of good bacteria in our diets, of course, is dahi; something that the West only widely accepted in the later part of the 20th Century. The reason we add a little bit of dahi to milk before we leave it to set overnight is because the ready dahi contains bacteria (mainly, the same lactobacillus family we find in dosa batter) that reproduces rapidly and turns the milk into more dahi.


   In Eastern Europe (and parts of the Middle East), the benefits of dahi have long been recognised. But Indians may have been the first to guess that there was an added complication. While there may be bacteria in the starter culture, as the dahi sets, it also attracts bacteria from the atmosphere. It is these bacteria that give the dahi its distinctive taste. Because the kinds of bacteria in the atmosphere vary from place to place, so does the taste of the dahi. Even if you use the same starter culture, the dahi you make in say, Madurai, will not taste exactly the same as the dahi you make in say, Ludhiana.


   I spoke to Dr Issac Mathai of Soukya, probably the most globally famous Indian exponent of traditional medicine and alternative healing. (Prince Charles went to Soukya in Bengaluru. The Duchess of Cornwall is a regular etc.) Dr Mathai recognises how the bacterial composition of dahi can vary from place to place. But in medical terms, he does not think that this is a bad thing. In fact, when patients come to him with digestive problems he often recommends that they have a little home-made dahi, first thing in the morning. (Commercial dahi either has no live bacteria or, even in fancy health-food brands, a bland bacterial composition that does not really reflect the environment you live in.)


   Dr Mathai's is a sensible and effective low-cost prescription because lactobacillus, the main bacterium in dahi has been proven to help in digestion.


   But do all bacteria help in digestion? And even if you are sticking to so-called good bacteria, how much do you need to consume for there to be a beneficial effect?


   Well, most of the foods regarded as containing ‘good’ bacteria carry some version of lactobacillus or its cousins – kimchi and sauerkraut for instance. Even idlis and dosas rely on lactic acid bacteria of various forms.


   And indeed the bacterium that gives sourdough its khatta taste (well, real sourdough should have that taste; most Indian versions don’t) is also a version of lactobacillus. The difference between dahi and kimchi and products that are subject to heat (like bread and dosas) is that most bacteria are killed off doing the heating process. So while bacteria play a huge role in imparting flavour to dosas, very few Indians recommend dosas as health foods.


   So, it should be with sourdough. Even if some probiotics survive the cooking process, there are not enough of them to make any real difference to your health.


   The role of bacteria in our gut is a subject that scientists are still studying. New research suggests that many of the things we don’t understand – why some of us become fat, for instance – are linked to levels of bacteria in our system.


   As the research progresses, we will learn more. Till then, eat dahi. But don’t fall for the ‘health’ claims made for every food that may contain some bacteria.



Posted On: 06 Feb 2021 11:38 AM
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