Category: umami hypothesis

A new paper in Nature Genetics describes research into the bacteria in ancient teeth plaque. When modern food came along, the bacteria became less diverse. One of the researchers said:

The composition of oral bacteria changed markedly with the introduction of farming, and again around 150 years ago. With the introduction of processed sugar and flour in the Industrial Revolution, we can see a dramatically decreased diversity in our oral bacteria, allowing domination by caries-causing strains.

Whether the decrease in diversity was due to (a) more sugar and flour or (b) less bacteria-laden foods is hard to say.

Again, data suggest we need bacteria to protect us against bacteria. You’d never know this from food safety laws or how freely pediatricians prescribe antibiotics. Again, it is hard to know without more research what caused this or that historical change in health (e.g., more tooth decay when sugar and flour became popular). The obvious answer (e.g., sugar causes tooth decay) might be wrong. If you believe that cavities are caused by too much sugar, the solution is to eat less sugar. What if cavities are caused by not enough bacterial diversity? Then other solutions might work better, such as eating more fermented food.

Thanks to Vic Sarjoo.

A new study has found that fecal transplants work better than antibiotics for clearing up a common and dangerous infection:

Such transplants cured 15 of 16 people who had recurring [= difficult-to-get-rid-of] infections with Clostridium difficile bacteria, whereas antibiotics cured only 3 of 13 and 4 of 13 patients in two comparison groups.

Clostridium difficile infections often result from antibiotic treatment. It is a big step forward for modern medicine to manage to grasp that the bacteria in our bodies protect us from infection. Here is a blog about the value of fecal transplants; here is another blog.

The comments contain many interesting details: Continue reading “Fecal Transplant Roundup”

I became interested in the health value of fermented foods after I noticed a curious coincidence. Humans have three mysterious food preferences: for (a) sour food, (b) food with umami flavor, and (c) food with complex flavor. I realized that all three preferences made bacteria-laden food more attractive. Bacteria change sugars to acids, increasing sourness. They break down proteins, creating glutamate, which produces umami flavor. And the many chemicals they introduce into a food make its flavor more complex. After I noticed this, I came across many studies that supported the idea that fermented foods are good for health. I also found studies that suggest the bacteria in our digestive system are crucial to health.

This raised the question: What fermented foods to eat? How many? How often? To begin to answer these questions, it would help to know how bacteria in our food help us be healthy. There were two obvious answers:

1. Stimulate the immune system. The bacteria in fermented food are inherently safe: they are specialized to reproduce on/in food, which is so different than inside the human body.  But the immune system doesn’t know this. If this was one benefit of fermented food, you could study which ones to eat by measuring immune system activation. Unfortunately, that is nearly impossible.

2. Improve digestion. Many people have digestive problems and some of them are helped by fermented foods. Obviously they contain bacteria that digest food. I don’t have digestive problems so I can’t study this by figuring out which fermented foods help.

Recently, I have begun to think there is a third reason:

3. Place competition. To make us sick, outside bacteria need to stick inside us. To digest our food, the surfaces of our digestive system, such as the inside of our intestines, is much more porous than other surfaces, such as our skin. It is our digestive system, therefore, that is most vulnerable to dangerous microbes. The totally-safe microbes in fermented foods compete for sticky spots with other, more dangerous microbes. If there are plenty of safe bacteria — say, billions in a serving of yogurt — they may do a lot to protect us against the dozen or so similar dangerous bacteria we might get from touching the same surface as a sick person. I think of a wooden floor where the lumber is not quite well-fitted. If you want to protect what’s below that floor from black sand (dangerous), an excellent method would be to pour an enormous amount of white sand (safe) on the floor.

If Effect #3 (place competition) is the main reason fermented food protects us from disease, it implies that dead bacteria work as well as live bacteria (in contrast, live bacteria do not digest food, Effect #2). This might explain the potency of alcoholic beverges such as wine, where most of the bacteria are dead. It also suggests that what matters is diversity of where bacteria stick and how much they stick. It might someday be possible to feed people (non-radioactive) bacteria and learn where in the body they end up.

 

 

One of the main reasons I think we need to eat fermented foods to be healthy is that their flavors correspond neatly to the flavors we like. Fermentation of fruits and other sweet foods changes sugars to acids, making the food taste sour — and we like sour food. Fermentation of proteins produces glutamate, which produces an umami flavor — and we like umami-flavored food. With many foods, their fermentation produces many microbial byproducts, giving the food a complex flavor — and we like complex flavors.

The connection between fermentation and complex flavor is well-put in a Saveur article about fermented foods:

[As a child] I only knew Claussen and other vinegar-cured pickles, the kind you buy in jars off the supermarket shelf, and I liked them just fine. But when I finally tasted a real pickle—the kind made the old-fashioned way, fermented with nothing more than salt, water, and time—I realized what I had been missing. A vinegary pickle plows through your palate with its tartness (often in a most pleasing way), but a live-cultured, salt-cured, fermented one tells a more multifaceted story. It is sour, to be sure, but it tastes of something more, something elusive: It’s the flavor of Middle Europe captured in one bite. When I started cooking for a living, I realized that the complexity I’d tasted in that pickle is the hallmark of well-made fermented foods, which include some of my very favorite things to eat and drink: not just pickles, but aged cheeses, tangy sourdough breads, blistering kimchis, tart yogurts, winy salamis, and of course, wine itself.