Category: umami hypothesis

The Hygiene Hypothesis (continued)

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In this NY Times Op-Ed, Jessica Snyder, author of Good Germs, Bad Germs, agrees with my comments about the hygiene hypothesis:

In 1989, an epidemiologist in Britain, David Strachan, observed that babies born into households with lots of siblings were less likely than other babies to develop allergies and asthma. The same proved true of babies who spent significant time in day care. Dr. Strachan hypothesized that the protection came from experiencing an abundance of childhood illnesses.

Dr. Strachan’s original hygiene hypothesis got a lot of press. . . Less publicized was the decade-long string of follow-up studies that disproved a link between illnesses and protection from inflammatory disorders like allergies and asthma. If anything, studies showed, early illness made matters worse. . .
Still, Dr. Strachan’s original observation was confirmed — as a group, babies in large families and day care are less likely to develop allergies and asthma than are children born into smaller families and kept at home. The same protective effect can be seen in children born on farms and in areas without public sanitation.

But the link isn’t disease-causing germs. It’s early and ample exposure to harmless bacteria — especially the kinds encountered living close to the land and around livestock and other young children. In other words, dirt, dung and diapers. Just as disease-causing microbes clearly bring on inflammation, harmless microorganisms appear to exert a calming effect on the immune system.

No mention of fermented food.

Thanks to Michael Bowerman.

The Hygiene Hypothesis

Seth Roberts3 Comments

Here is a nice review of the hygiene hypothesis, proposed in 1989 by David Strachan. The hygiene hypothesis is that the increases in childhood allergies and asthma in rich countries were due to decreases in “infection in early childhood, transmitted by contact with unhygenic older siblings or acquired prenatally.” It was inspired by the observation that allergies and asthma were less common in larger families.

In the original, it was infections that were the crucial thing you got from older siblings. This idea ran into trouble when actual measurements of number infections did not show the expected inverse correlation:

When a composite index of exposure was generated by combining histories of illness due to measles, mumps, rubella, varicella, and pertussis, the tendency was for a slightly higher risk of allergic disease in children with multiple infections.

Also bad for the infection idea is that vaccination for measles didn’t protect against hay fever or eczema.

It looks to my perhaps-biassed eyes that it is dirt (= harmless foreign proteins and bacteria) exposure that matters, not exposure to human infectious agents. Living on a farm helps. Plainly you get dirty living on a farm and exposed to animal viruses and bacteria — but that you get human infectious agents from pigs and cows is unlikely. (In technical terms, they aren’t vectors.) Older brothers are more protective than older sisters. Boys are dirtier than girls; it isn’t obvious they are more infectious. Dogs are more protective than cats. Again, dogs are obviously dirtier than cats but the notion that they are more infectious — few infectious agents cross the species barrier — is less obvious.

An emphasis on dirt rather than human-infectious agents is more compatible with my belief in the vast importance of ingesting bacteria-laden food.

Scary Effect of Food Irradiation

Seth Roberts2 Comments

Continuing the theme that wiping out bacteria — as antibiotics do — might be a bad thing, here is a mysterious development:

The new study arose from a mysterious affliction of pregnant cats. A company testing the effects on growth and development in cats using diets that had been irradiated reported that some cats developed severe neurological dysfunction, including movement disorders, vision loss and paralysis. Taken off the diet, the cats recovered slowly, but eventually all lost functions were restored.

“After being on the diet for three to four months, the pregnant cats started to develop progressive neurological disease,” says Duncan, a professor of medical sciences at the UW-Madison School of Veterinary Medicine and an authority on demyelinating diseases. “Cats put back on a normal diet recovered. It’s a very puzzling demyelinating disease.”

Do Americans have bacteriophobia? I believe we need to eat plenty of bacteria-rich food for best health (the umami hypothesis). If so, then irradiating food is like taking all the vitamins out of it. Of course, food irradiation is big business. From a list of FAQs:

4. Does eating irradiated food present long-term health risks?

No. Federal government and other scientists reviewed several hundred studies on the effects of food irradiation before reaching conclusions about the general safety of the treatment. In order to make recommendations specifically about poultry irradiation, U.S. Food and Drug Administration scientists reviewed findings from additional relevant studies.

Independent scientific committees in Denmark, Sweden, United Kingdom and Canada also have reaffirmed the safety of food irradiation. In addition, food irradiation has received official international endorsement from the World Health Organizations and the International Atomic Energy Agency.

The International Atomic Energy Agency. It’s an interesting methodological question: Is Diet X (irradiated food) “safe” because it is no worse than Diet Y (ordinary food)? What if Diet Y isn’t safe?

Duncan, the researcher quoted above, said this:

“We think it is extremely unlikely that [irradiated food] could become a human health problem,” Duncan explains. ”We think [what happened to the cats] is species specific.”

Hmm. If you don’t understand what causes the effect, how can you make strong claims about it? I think food with too-few bacteria is already a human health problem.

Thanks to Peter Spero.

What Did Eskimos Eat?

Seth Roberts13 Comments

In the early 1900s, the anthropologist/explorer Vilhjalmur Stefansson, after living with Eskimos for a long time, returned to tell Americans what he had learned about nutrition. Eskimos ate meat almost exclusively, he said, which contradicted the usual emphasis, then as now, on diversity and fruits and vegetables. Yet Eskimos were healthy. Eskimo diet became even more fascinating when it was realized they had very low rates of heart disease — much lower than Danes, for example. In the 1970s, two Danish doctors, Bang and Dyerberg, found that Eskimos had large amounts of omega-3 fats in their blood, much more than Danes; that was the beginning of the current interest in omega-3 and the idea that fish and fish oil are “heart-healthy”.

As I pointed out earlier, discussions of the Eskimo diet have ignored the fermented food they ate. Here’s what Stefansson said in 1935:

I like fermented (therefore slightly acid) whale oil with my fish as well as ever I liked mixed vinegar and olive oil with a salad. . . .

There were several grades of decayed fish. The August catch had been protected by longs from animals but not from heat and was outright rotten. The September catch was mildly decayed. The October and later catches had been frozen immediately and were fresh. There was less of the August fish than of any other and, for that reason among the rest, it was a delicacy – eaten sometimes as a snack between meals, sometimes as a kind of dessert and always frozen, raw. . . .

[At first, Stefansson didn’t want to eat decayed fish.] While it is good form [in America] to eat decayed milk products and decayed game [well, well], it is very bad form to eat decayed fish. . . . If it is almost a mark of social distinction to be able to eat strong cheeses with a straight face and smelly birds with relish, why is it necessarily a low taste to be fond of decaying fish? On that basis of philosophy, though with several qualms, I tried the rotten fish one day, and if memory serves, liked it better than my first taste of Camembert. During the next weeks I became fond of rotten fish.

So Eskimos ate fermented whale oil and a lot of rotten fish. (“A lot” because if they didn’t eat a lot of it, Steffanson wouldn’t have felt pressure to eat it.) I had no idea that Americans used to eat decayed game.

Autism and Digestive Problems

Seth Roberts3 Comments

A new study in Pediatrics has a brief but useful summary of the evidence linking autism and digestive problems. Here’s one study. Here’s a review, with this abstract:

Recent publications describing upper gastrointestinal abnormalities and ileocolitis have focused attention on gastrointestinal function and morphology in [autistic] children. High prevalence of histologic abnormalities in the esophagus, stomach, small intestine and colon, and dysfunction of liver conjugation capacity and intestinal permeability were reported. Three surveys conducted in the United States described high prevalence of gastrointestinal symptoms in children with autistic disorder.

There is also evidence that immune dysfunction is associated with autism.

I believe that few people in America eat enough bacteria — in practice, this means not enough fermented food — and that this causes digestive and immune problems. A vast number of people will say, “of course, good food is really important, bad food causes X, Y, and Z” — where X, Y, and Z can be practically anything. The difference between my views and theirs is the prescription: They inevitably think that people should eat more fresh unprocessed food. (Usually fruits and vegetables, for some curious reason.) Fermented food, of course, is not fresh and not unprocessed.

Bacteria and Learning?

Seth Roberts2 Comments

Do bacteria-laden foods improve learning? A recent study:

The ability of dietary manipulation to influence learning and behavior is well recognized and almost exclusively interpreted as direct effects of dietary constituents on the central nervous system. The role of dietary modification on gut bacterial populations and the possibility of such microbial population shifts related to learning and behavior is poorly understood. The purpose of this study was to examine whether shifts in bacterial diversity due to dietary manipulation could be correlated with changes in memory and learning. Five week old male CF1 mice were randomly assigned to receive standard rodent chow (PP diet) or chow containing 50% [raw] lean ground beef (BD diet) for 3 months. As a measure of memory and learning, both groups were trained and tested on a hole-board open field apparatus. Following behavioral testing, all mice were sacrificed and colonic
stool samples collected and analyzed by automated rRNA intergenic spacer analysis (ARISA) and bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP) approach for microbial diversity. Results demonstrated significantly higher bacterial diversity in the beef supplemented diet group according to ARISA and bTEFAP. Compared to the PP diet, the BD diet fed mice displayed improved working (P = 0.0008) and reference memory (P < 0.0001). The BD diet fed animals also displayed slower speed (P < 0.0001) in seeking food as well as reduced anxiety level in the first day of testing (P = 0.0004). In conclusion, we observed a correlation between dietary induced shifts in bacteria diversity and animal behavior that may indicate a role for gut bacterial diversity in memory and learning.

Previous studies had found that changes in diet changed behavior. This article says that changes in diet can produce changes in bacterial diversity and these bacterial changes might have caused the behavior changes.

Eventually I will stop eating lots of fermented food and see what happens. Perhaps my arithmetic scores will get worse.

Where Does Umami Come From?

Seth Roberts1 Comment

As previously blogged, the evolutionary reason we like umami taste may be so that we’ll eat more bacteria-laden food. This makes sense only if bacteria-laden food would have been the main source of umami. Nowadays, you can get umami from MSG. What about before MSG?

The Umami Information Center sent me a free booklet called Umami The World — a better title than Umami: An Introduction. Umami taste is mainly supplied by glutamic acid, a protein building block. My assumption was that glutamic acid is usually a protein breakdown product. Bacteria feed on protein, leaving a pile of bricks — glutamic acid among them. Was this correct? Or could you get umami taste without bacteria?

You can, but in most cases you don’t. In Japanese cooking, a potent source of umami is konbu, a type of seaweed. Perhaps because konbu produces so much umami and so little else that umami was discovered by a Japanese scientist. Umami flavorings are used in many other cuisines but the source is usually fermented food. In many Asian countries, umami comes from fermented fish sauce and fermented bean products (e.g., miso, soy sauce). In Chinese cooking, umami comes from a condiment called jiang, which is made from fermented grain, meat, or fish. In Western cuisines, cured pork is often used as a flavoring agent. “The curing process liberates more of the glutamic acid content of the meat.” Curing takes place at room temperature, which means bacteria grow. “Much of the food of ancient Rome was routinely seasoned with a sauce [that] was made from salted fish, fermented and strained. . . The polar Eskimo people traditionally fermented a small portion of their harvest of fish.” Tomatoes and shitake mushrooms are non-fermented sources of umami.

A telling comment in the book is that umami usually comes from sauces (e.g., fish sauce) or liquids (e.g., dashi, bouillion). Cooks use sauces and liquids to add what is missing. The presence of umami in so many sauces — as if sauces have been devised or selected to be high in umami — suggests that ordinary foods don’t have much umami. A table of glutamate concentration says that parmesan cheese has 1700 mg/100 g whereas several vegetables — tomatoes (246 mg/100 g), green pea (106), onion (51), spinach (48), potato (10) — and meats — beef (10), chicken (22), pork (9) — have much less.

The breakdown process I imagined is spelled out: “During the ripening of cheese, proteins are broken down progressively into smaller polypeptides and individual amino acids. Large increases in free amino acid content also occur during the curing of ham.” Surely the same will be true during room temperature aging of any protein source. Beef is routinely aged at room temperature for about a week to give it a “meaty” flavor (not from the umami book but from here).

Umami Burger

Seth Roberts4 Comments

A new restaurant with the excellent name Umami Burger has just opened in Los Angeles. According to The Foodinista, the food is as good as the name:

An attractive space with an attractive clientele. The tightly edited menu consists of 10 burgers, and a few sides including fries and a market salad. But, we’re told at 12:45 pm on a Tuesday afternoon, they’ve run out of buns. . . . amazing homemade ketchup . . . The beef patties on all of the above, really flavorful and just plain GOOD. I don’t know how they can make such a great burger and charge so little. . . . I’m telling you, the burgers are great.

Review by Jonathan Gold.
Thanks to Tucker Max.

Shades of Homeopathy! Peanut Allergy Cured . . . With Peanuts

Seth Roberts2 Comments

Doctors at Addenbrooke’s hospital in Cambridge gave four children tiny doses of peanut flour every day, gradually increasing the dose until now they can eat ten or more nuts a day.

Previously the children would have risked anaphylactic shock or even death if they accidentally ate even a trace amount of peanut.

The team say this is the first time that so-called desensitization treatment has been successful.

From the Telegraph. Notes: 1. No blinding. 2. No control group. 3. Started small (with 4 patients), now doing a larger study (18 patients). 4. Jewish kids in Israel have a 10-fold lower rate of peanut allergies than Jewish kids in the UK, according to a 2008 study. In Israel, peanuts are eaten at an earlier age.

Thanks to Oskar Pearson.