Gut: The Inside Story of Our Body's Most Under-Rated Organ

by Giulia Enders

As it happens, the higher the hygiene standards in a country, the higher that nation’s incidence of allergies and autoimmune diseases.

But if you dilute the bacteria on your plates, cutlery, and cutting board nicely with water, and then wipe them over with a kitchen sponge before putting them away, you may as well have licked them clean with your tongue. Kitchen sponges offer the perfect home for any passing microbe — nice and warm, moist, and full of food. Anyone looking at a kitchen sponge under the microscope for the first time usually wants to curl up on the floor in the foetal position, rocking back and forth in disgust. Kitchen sponges should only be used for cleaning the worst of the dirt off — plates, cutlery, and so on should then be rinsed briefly under running water.

Bacteria cannot breed on dry surfaces. Some cannot survive there at all. A freshly mopped floor is at its cleanest after it has dried. Armpits that are kept dry by antiperspirants are less cosy homes for bacteria — and fewer bacteria produce less body odour. Drying is a great thing. If we dry food it keeps for longer before it rots. We use this to our advantage: just think of foodstuffs like pasta, muesli, crispbread, dried fruit (such as raisins), beans, lentils, and dried meats.

The optimum temperature for your fridge is something below 5°C.

However, damp kitchen cloths, a load of underpants, or sick people’s laundry should be washed at 60°C or more. Most E. coli bacteria are killed by temperatures above 40°C; 70°C is enough to kill off tougher salmonella bacteria.

Since our skin produces a natural coating of fat, it’s often enough to achieve this effect by using soap and water. Some of the fat layer remains, aiding its replenishment after washing. But too-frequent hand washing makes no sense — and the same is true of too-frequent showering. If the protective fat layer is rinsed away too often, our unprotected skin is exposed to the environment. This gives odour-producing bacteria a better foothold, making us smell more pungently than before: a vicious circle.

Not far away, across the border in Germany, the same method is in use in the public toilets of the small town of Düren. A company is using a mixture of bacteria to clean the toilets. The odourless bacteria occupy the places normally colonised by the bugs that create that all-too-familiar public-toilet smell. The idea of using bacteria to clean public conveniences is a brilliant one. Unfortunately, the company refuses to reveal the recipe for its cocktail of bacterial cleaners, so a scientific evaluation is impossible. However, the town of Düren seems to be faring very well with this experiment.

These new ideas about the use of bacteria illustrate one thing very clearly: cleaning does not mean annihilating all bacteria. Cleanliness is a healthy balance of sufficient good bacteria and a few bad ones.

Take care abroad. One holidaymaker in four returns home carrying highly resistant bacteria. Most of these bugs disappear in a few months, but some lurk around for much longer. Special care should be taken in bacterial-problem countries like India. In Asia and the Middle East, you should wash your hands regularly, and clean fruit and vegetables thoroughly — if necessary, with boiled water. Southern Europe also has its problems.

Fresh sauerkraut is usually only sold in specialist healthfood stores these days.

Mothers who were unable to breastfeed their babies found they often had a problem with their bottle-fed offspring. The babies were getting diarrhoea much more often than they should. This took the formula milk industry by surprise, because they had taken care to make sure their product contained the same substances as real breast milk. What could be missing? The answer was, of course, bacteria! Bacteria that live on milky nipples, and which are particularly common in the guts of breastfed babies:

There are studies that show their effects, but they are not sufficient to satisfy the European Food Safety Authority. It has banned companies like Yakult and Actimel from claiming in their advertising that their products promote health. These doubts are compounded by the fact that it is not always possible to know whether enough probiotic bacteria are reaching the large intestine alive. A break in the cold chain, or a person with a particularly acidic stomach or slow digestion, might kill off these microbes before they reach their intended destination.

Bad bacteria cannot process prebiotics at all, or hardly, and so they cannot use prebiotics to produce their evil chemicals. At the same time, good bacteria fed with prebiotics grow constantly in power, and can gain the upper hand in the gut.

Fig.: Artichoke, asparagus, endive, green bananas, Jerusalem artichoke, garlic, onion, parsnip, black salsify, wheat (wholegrain), rye, oats, leek

What the researchers are interested in is not the blues themselves, but how we react to them. This is among the most accurate indicators of whether a healthy person might develop depression or not. Above all, studies have repeatedly shown that the least favourable reaction is fretful brooding — about who might be to blame for our woes, for example.

While mood can be seen as originating in various parts of our nervous system, stress is better described as the state the nervous system is in.

The current state of research indicates that our gut has about a 10-to-15 per cent influence on feelings of melancholy, anger, or stress.