Or, “When I’m down, I feel that everything is hopeless.”
In the fine old tradition of test questionnaires, the subjects were given the following five options to rate on a scale of 0 to 4: Nope, never really / Rarely / Sometimes / Often / Oh yes — absolutely!
Before they began taking the bacteria, the test subjects’ average scores were about 43 out of a total of 136 points. Thus, they were within the healthy average range and did not display any brooding, angry, or despairing tendencies. They then took the bacteria mixture every day for four weeks. Mouth open, powder in, swallow it down. The group that were given a placebo (without their knowledge) barely changed their responses at all. But those who took the real bacteria improved their scores—in particular, in two areas, anger and brooding—by about 10 percent at least (which means roughly half the questions in those areas were answered one degree more positively).
This is not the same effect as would have been achieved if they had been given cocaine—or a powerful tranquilizer—but it is also not the same effect as that of the placebo. Results like these lead us to the question of how great the gut’s influence on our mood is. They also raise the question of what aspects of our mood it can affect.
Stress
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. A stressed nervous system is like a taut bowstring—in a constant state of alertness and sensitive to any external stimulus. Such a state is excellent for tackling an obstacle course or reacting to a dangerous situation while driving. However, as a permanent condition, such a state is pretty costly. . . comparable to taking a monster truck to drive to the supermarket around the corner. The gut lends the brain a large amount of energy in order to deal with the stress (see page 133). Could our guts also help relieve feelings of stress? As a way of helping themselves, so to speak?
In this field, the wait for newer results has been worth it, as the research has changed tack. The initial conclusion following the first experiments with human subjects was that a stressful daily routine or a scary exam was always equally stressful or frightening for subjects, no matter which lovely bacteria they fed to their guts. However, it was concluded, microbes could help reduce the physical effects of stress, such as stress hormone levels, nervous stomach aches, nausea, diarrhea, and susceptibility to colds.
However, a closer examination of those studies reveals an interesting indication. One species of bacteria also altered people’s subjective level of stress—although this appeared to be the case only in one subgroup of subjects: the sleep-deprived ones. Those who slept less in the run-up to an exam were always more stressed. This effect was less pronounced among subjects who swallowed a daily dose of Bifidobacterium bifidum. They were still stressed—but a little less so than their peers who slept equally badly but did not get the bacterium.
In this study, 581 subjects were divided into four groups a couple of weeks before the study began. One group received capsules containing a powder with no bacteria; the other three groups were each given a different type of bacteria: Bifidobacterium bifidum, Lactobacillus helveticus, and Bifidobacterium infantis. Lactobacillus helveticus and Bifidobacterium infantis, however, did not show the same effect as Bifidobacterium bifidum.
The result with Bifidobacterium bifidum encouraged scientists to investigate the microbial world in more depth—after all, a bacterium had now been found that managed something no other bacterium had been shown to do: reduce feelings of stress. It was not long before new results emerged from Ireland. Some researchers—those who had also carried out the experiment with the swimming mice (see page 126)—now ventured into the arena of human trials. One particular Bifidobacterium (Bifidobacterium longum 1714) had shown itself to be highly effective in their experiments with mice. It reduced stress parameters and improved the lab animals’ memory. So the Irish scientists tested it on a small group of human animals.
The participants in this study were asked to fill out an online questionnaire about their feelings of stress every day. They were also called into the lab three times within a period of eight weeks, in order to do the following:
1.Put on a funny helmet.
2.Plunge one of their hands into ice-cold water.
3.Solve mental puzzles on a tablet PC.
THE FUNCTION OF the funny helmet was to measure the activity levels in various parts of the subjects’ brains. If you were to make your beloved wear this helmet while you were telling him or her about your boring day at the office, you would be able to watch as the level of activity in the listening area of their brain slowly declined and the day-dreaming regions revved up for a party.
Plunging subjects’ hands into unbearably cold water is a tried-and-true method of assessing their stress levels. A measurement is taken of the amount of time subjects are able to keep their hands in the icy water, while swabbing their mouths regularly with cotton buds. The cotton buds absorb saliva, which can be analyzed to measure the amount of stress hormones it contains. No matter how often the test is repeated, the subjects’ reactions are always the same. A nervous system that signals stress due to cold is not a creature of habit—it does not get less sensitive over time when exposed to low temperatures repeatedly or for a long period of time. If it did, we would perceive the weather as getting increasingly warmer as winter progressed.
As soon as the test subjects had had enough and rescued their hands from their freezing fate, they were asked a number of questions. The researchers wanted to know how anxious they felt immediately after experiencing a rush of excited hormones.
Almost every parameter was different in some way after a four-week course of Bifidobacteria. In the online questionnaires, the test subjects reported around 15 percent lower levels of day-to-day stress, as compared with the subjects who received a placebo. The cold-water, hand-immersion test still triggered the same reaction (as expected—after all, the water was still freezing cold), but with an overall stress hormone level that was lower than before. Furthermore, those hormones did not lead to increased anxiety.
The electrode helmet and tablet-based teasers were also not simply for the researchers’ amusement. The “bacteria group” made around two to five fewer mistakes in the memory tasks, compared with the placebo group (who made one to three fewer mistakes)—already a successful result. This effect was also made visible by the helmet. One area of the brain that we use for learning, and which becomes weaker in patients with Alzheimer’s, now showed increased activity. The placebo had no such effect—but with the bacteria, it was clear.
Our gut can send impulses to the brain—for example, via nerve fibers (see page 126). The Irish research team came up with another possible explanation—bacteria could have improved memory function by reducing the subjects’ stress-hormone levels. That might work like this: the brain structure that stores our memories and links them to each other (the hippocampus) is very densely populated with sensors that detect stress hormones. If the hippocampus registers large amounts of such hormones, the brain cuts back the level of activity there. After all, if you are running away from a wild animal, you don’t need to waste energy remembering which plants you pass by. During stressful times in our lives, we develop a kind of tunnel vision—to enable us to direct our attention to the problem at hand.
This observation is interesting—not only for fans of Bifidobacterium longum 1714, but also for patients with gut conditions who find it difficult to concentrate as well as usual during a flare-up, and for school students, for example, who have trouble cooperating with their brains during a tough test. In the end, it may not really matter whether the state of stress is reported by the gut or the brain. Both organs are able to use the nervous system and messenger substances in the blood to stimulate the adrenal gland (the organ that eventually produces stress hormones). And this is precisely where we may return to the issue of mood.
Let’s go back to those little, day-to-day downers studied by the group of Du
tch scientists. Remember—no matter how nice our lives may be, we all have them from time to time. Those who tend to react to such a mood by brooding over their problems will find that our modern world offers a rich palette of problems to ponder. Even more importantly, these are often problems we can do nothing about. Some politician somewhere in the world says something stupid, but in the past hardly anyone would have got wind of it. Elsewhere, a plane comes down, killing an entire football team you would never otherwise have heard about. Someone or other puts a picture of her perfect life online, and we end up comparing ourselves unfavorably to something we would never have seen in the past.
If we engage in it enough, brooding over problems that cannot be changed can result in feelings of stress. The resultant stress hormones serve to increase that tunnel vision. And it becomes increasingly difficult for us to see anything beyond our own problems. And this, in turn, further increases our level of stress. Voilà: we have a vicious circle. A physiological system that was meant to help us in times of stress is thus co-opted, and we increasingly slide into a behavior pattern of “stressed griping,” rather than directly observing the world around us, asking inquisitive questions, or taking care of our well-being.
Depression
THE CURRENT STATE of research indicates that our gut has about a 10- to 15-percent influence on feelings of melancholy, anger, or stress. It tells the brain what is happening inside us, and that information may be worrying or reassuring. So it could be partly responsible when we slide into a certain mood. However, this says nothing about the extent of the gut’s involvement in the process of emerging from a period of fully fledged depression.
Preliminary experiments aimed at answering this question give cause for optimism. A group of Irish researchers, for example, harvested gut bacteria from people with depression and implanted them in rats. This is not the kind of microbial exchange that happens when you shake hands with someone: the scientists first removed all other microbes from the rats’ intestinal system and then administered highly concentrated doses of the harvested bacteria. The rats developed depressive behaviors that they had not displayed previously.
When it comes to purely human experiments, research is still at a very early stage. A common tool in such research is the Becks Depression Inventory psychometric test. This test helps scientists determine the severity of a patient’s depression (and, for example, whether they are dealing with a case of clinical depression or a temporary bout of the blues). Perhaps surprisingly, the list of twenty-one questions does not only ask respondents whether they feel sad or dissatisfied; it also includes questions about problems with sleeping, difficulty making decisions, increasing health worries, or a noticeable lack of interest in sex (compared with the past). Basically, these are indirect questions about the various hormone systems in our body.
So far, there are only two studies that have investigated, under controlled conditions, the effect of probiotic bacteria on depression. The first study, in 2015, found that a combination of two kinds of bacteria (Lactobacillus acidophilus and Bifidobacterium bifidum) and medication improved patients’ condition, but the effect was slight once all possible interference factors were removed from the calculations. And a study in 2017 found that two types of bacteria (Lactobacillus helveticus and Bifidobacterium longum) had no influence on depression. However, the researchers did find an indication that a patient’s vitamin D level may influence this effect. In test subjects with sufficiently high levels of vitamin D in their blood, the microbes appeared to improve their mood; however, the overall number of subjects was too small to allow a scientific conclusion from this study.
These are the first two steps on a new journey in research. If we continue down this path, we will eventually see which way it is leading us. Could we perhaps use the gut to prevent depression before it occurs? Are bacteria better suited as a complementary treatment, to be used alongside medication, therapy, and lifestyle changes? Or should treatments for depression perhaps target multiple possible causes at once—that is, the gut (via bacteria and diet), the brain (with drugs and therapy), and other possible causes (such as vitamin levels, physical activity, or working conditions)? It may also be the case that there are many different kinds of depression—some for which the influence of the gut is greater and therefore more important in their treatment, and others for which this is not the case.
The goal of this journey should not be to discover some kind of super-bug, which we would all take a daily dose of. The aim is also not to produce a population of permanently happy people. Rather, the aim should be to reach a better understanding of our bodies and how we live in them. This includes being aware of what is going on inside our bodies, rather than looking only for external causes of stress or mood swings. If we were to discover particularly effective microbes to support us along the way, that would be an excellent thing. But while scientists are still searching through the fog, we should learn to appreciate what we already have: good microbes inside us and around us, and ancient knowledge, to which we should pay much more heed.
Clever Cravings for Fermented Foods
SOMETIMES IT IS not necessary to understand our desires and cravings. If a person occasionally enjoys rolling around on their living-room floor for no apparent reason, let them. However, it can sometimes be both useful and interesting to find out why we develop the desire to eat and drink what we do.
Take a glass of water and add an equal amount of sugar to that contained in the same volume of cola. Few people would want to drink the resulting mixture. And if we did, we would probably feel disgust at the idea of downing a second glass. This is because our bodies are cleverer than we think.
If we now do something that several million years of evolution has not been able to prepare us for, the experiment ends with a very different result. If we add a little citric acid to the sugar water (represented by carbonic and phosphoric acid in cola)—hey presto! We have a delicious drink. We down the glass in one gulp, and our brain claps its hands in delight: hooray!
Our bodies are familiar with acid, from fruit and good bacteria (for example, the lactic acid bacteria in yogurt). When the acid is not too strong and comes in combination with other nutrients, it gains the trust of our taste buds. Thus we like to include an acid component when we cook a pleasant-tasting meal—tomatoes in the sauce, a squeeze of lemon over the fish, a glug of wine over the frying onions. This well-placed pleasure is fascinating for anyone with an interest in microbes. A pertinent question might be: when we fancy a sour ingredient in our meal, are we really craving good bacteria?
Down the millennia of history, anyone with a yen for a taste of sour would satisfy their hunger with good microbes. Our forebears fermented cabbage to create sauerkraut and drank wine rather than water (which was usually too contaminated to drink untreated in the Middle Ages). They still baked their bread using real sourdough, and made their own sour milk and yogurt products. They did not have access to citrus fruits or acidified carbonated drinks. This observation gives cause for a little experiment you can carry out for yourself.
Fermenting Vegetables with Bacteria at
Home—AKA Making Sauerkraut
FERMENTING MEANS GETTING bacteria to pre-digest your food. Bad bacteria and molds do not ferment your food nicely, but spoil it and render it inedible. Good bacteria, however, process our food to make it easier for us to digest. They are better than our digestive enzymes at splitting open cabbage cells (or other plant cells). In this way, they make the work of the gut much easier and even produce additional vitamins in the process. They also produce acids that kill off any dangerous bacteria, thus preserving the food for longer. Since good bacteria are everywhere, just hanging around in the environment, it makes sense to provide them with a useful job to do and something to eat. This helps them multiply and gain more power.
1.Cabbage is the classic, but almost any vegetable that can be eaten raw can also be fermented. Carrots and gherkins, for example (gherkins are the pinnacle of pickling, howeve
r, as precise procedures must be followed if they are to remain crisp to the bite). Some good bacteria will already be on the cabbage leaves or the skin of the carrots, so there is no need to add any particular bacteria to them. This is why it can be beneficial to buy vegetables that have not been treated with pesticides, etc.
2.Depending on how long you want the fermentation process to take, slice your vegetables thinly or grate them (= one week’s fermentation time) or leave them whole (= four to six weeks’ fermentation time). You need to make sure you avoid contamination as you work. You don’t want just any old kitchen bacteria joining your product in the jar.
3.Add one-third of an ounce to half an ounce (10 to 15 grams) of salt for every 2.2 pounds (1 kilogram) of vegetables. This slows the growth of bacteria in general, preventing bad germs from commandeering the process before the good ones can do their work. It is important to add the correct amount of salt: too much will prevent the fermentation process altogether; too little can result in the food going off and tasting bad. Sea salt is a good choice, but do not use iodized salt under any circumstances as the iodine inhibits the bacteria’s growth too much.
4.Knead the mixture with appropriate fervor. This is to thoroughly mix the salt into the concoction and to help partially break down particularly tough cell walls. The salt helps extract the water from the cabbage cells, which can be used later as the pickling liquid.
5.Press the cabbage firmly into a jar with an airtight seal. It is important to make sure that all the vegetable matter is submerged beneath the liquid so that it is not exposed to oxygen, which disturbs the fermenting bacteria. Any parts that stick out above the liquid will not be protected by the acid and could go moldy. If your cabbage or carrots have not produced enough liquid of their own to cover them completely, you can add more salted water. Add a generous teaspoon of salt for every 0.85 ounces (250 ml) of water. If there is still some vegetable matter sticking out above the surface of the liquid, you can add a weight to press it down. (Special “sauerkraut weights” are available, in Germany, at least!—but a rock or stone of the right size that has been cleaned by boiling it in water will do the job just as well.) Those who prefer a particular flavor to their sauerkraut can now add almost anything they want to the jar, such as caraway seeds, beetroot, or, particularly good with carrots, a little ginger.
Gut: The Inside Story of Our Body's Most Underrated Organ (Revised Edition) Page 22
