Seth's Blog

Here is a summary/directory of my posts about what I call the umami hypothesis — the idea that we must ingest plenty of microbes to be healthy. My Watts Towers. The easiest way to ingest plenty of microbes is to eat fermented foods.

• Probiotics reduce/prevent diarrhea caused by antibiotics. News article. The abstract says “The pooled evidence suggests that probiotics are associated with a reduction in AAD [antibiotic associated diarrhea].” It should say that the evidence suggests — very strongly, in fact — that probiotics cause a reduction in AAD (because there is no plausible alternative explanation of the association). This mistake is so elementary it is like saying 2 + 2 = 3. And JAMA is one of the world’s most prestigious medical journals.
• Living without money. The author was much healthier than when he lived with money. Among the many possible explanations is that dumpster food, old enough to allow microbes to grow on it, is healthier than fresher and therefore more sterile food.
• Not just farms. Children who grow up on farms have fewer allergies and less asthma than children who grow up in cities — important support for a modified version of the hygiene hypothesis (and my umami hypothesis). This study finds that living near other sorts of biodiversity provides similar benefits.

Thanks to Brody, Jazi Zilber and Mark Griffith.

• Difficulties repeating priming effects
• Unexpected benefits of yogurt in mice. “The yogurt-eating mice were incredibly shiny. . . . These animals had 10 times the active follicle density of other mice.”
• A 13-year-0ld invents a cure for hiccups.
• A business that sells starter cultures for yogurt, kefir, kombucha, and so on — even natto. Here’s a little secret: you shouldn’t need to buy starter cultures. The store-bought product (e.g., bottle of kombucha), if not pasteurized, should function as starter culture for yogurt, kefir, or kombucha.
• Amish farm kids have fewer allergies than Swiss farm kids. Suggesting that something besides growing up on a farm can reduce allergies. Drinking microbe-rich raw milk?

Thanks to Hal Pashler and Bryan Castañeda.

• The magic of mangoes. “In one double blind trial which included a low fat diet, the participants who took the mango supplements lost 5.3 per cent of their body weight while the control group lost only 1.3 per cent.” Which sounds impossible.
• Greek yogurt taste test
• Umami flavour as a means of regulating food intake and improving nutrition and health
• Babies fed breast milk have better intestinal microflora than babies fed formula. “Our findings suggest that human milk promotes the beneficial crosstalk between the immune system and microbe population in the gut, and maintains intestinal stability.”

Thanks to Melissa McEwen and Bryan Castañeda.

Alcohol is bad for your liver, we’re told. However, moderate amounts may be good for your liver. A recent meta-analysis found that men who drank moderate amounts of alcohol had considerably less risk (a risk ratio of 0.3) of liver cirrhosis than men who drank no alcohol.  It wasn’t clear if some forms of alcohol (e.g., wine) were more protective than others. I came across this study because another article called the association “biologically implausible”, whereas I think it is highly plausible due to vast experimental literature on hormesis (animals given small amounts of poisons are healthier than animals given none).

The findings about cirrhosis join a much large body of evidence that moderate drinking is associated with less heart disease.  A recent meta-analysis reached this conclusion once again and found, in addition, that moderate drinking is associated with less all-cause mortality.

These are more examples of the health benefits of fermented foods, one of my favorite subjects. It is unfortunate the liquor industry does not run long-term human experiments on the effects of moderate amounts of beer, wine, and so on.

It’s hard to get scurvy. If you eat anything resembling an ordinary diet you won’t get it. The existence of scurvy, produced by extreme conditions, led to the discovery of Vitamin C.  From the case of scurvy and Vitamin C we learned — well, most people learned — that some diseases are clues to what we need to eat to be healthy. (more…)

A new online open-access journal called Flavour has just started publication. The first issue has three articles and an editorial.

The journal

encourages contributions not only from the academic community but also from the growing number of chefs and other food professionals who are introducing science into their kitchens. . . . often in collaboration with academic research groups.

The first set of articles has an example of a collaboration between chefs and professional scientists — how to get a strong umami flavor from Nordic seaweed. Then you add the flavor to ice cream. Which reminds me of dessert at a friend’s house where he poured expensive balsamic vinegar on vanilla ice cream.

Thanks to Melissa McEwen.

• no detectable association between heart disease and fried-food consumption
• tiny amounts of alcohol greatly lengthen worm’s life
• climate models fail to predict ocean heat content
• disgust and fermented food

Thanks to Aaron Blaisdell, Alex Chernavsky and Navanit Arakeri.

When I taught Introductory Psychology, I came across a study in which researchers put people in a room with food and watched them. They were looking for cycles in eating and drinking. They noticed that their subjects spent a lot of time touching the face near their mouth — what they called “the snout area”. After I read that, I noticed the same thing countless times. Right now I am at an airport waiting for a flight. Looking around, I see three of about 50 people touching their mouth or nearby.

Why do we do this? I propose an evolutionary explanation:  To expose our immune system to all the germs near us in small amounts. Mouth-touching is part of a larger sampling process:  1. We touch many things constantly. In particular, we shake hands, hug, and otherwise touch people near us. Germs that have managed to live in or on other people are the most dangerous. 2. We lick our lips often, moving germs on our lips inside our mouths. 3.  When you eat, food transfers bacteria from the inside of your mouth to your tonsils, which circle your throat. Tonsils are full of lymphocytes, the immune-system cells that detect germs. Once we have developed antibodies to a microbe, of course, we are much less vulnerable to it. The whole sampling process is a kind of self-vaccination.

We need conventional vaccination when self-vaccination fails. Polio vaccination was the first big vaccination program, and it worked: polio was nearly wiped out.  Before around 1900, polio was not a big problem. It became a big problem at roughly the same time that public health measures and the replacement of horses by cars caused cities to become much cleaner places. Others have theorized that this is why polio became a big problem. As recently as 1951, thousands of children died from polio.

This is related to but different than my ideas about our need for fermented food. (I believe we need to eat plenty of fermented food, day after day, to be healthy.) When we eat fermented food, we ingest large amounts of bacteria that  are familiar and safe. The amount is large because the food has been fermented. The bacteria are familiar because we eat the same food repeatedly. They are safe because the insides of our bodies are dramatically different than  what we eat (e.g., different temperature).  The sampling system I am proposing here exposes us to small amounts of unfamiliar dangerous bacteria. However, this sampling system and the factors that push us to eat fermented food (our liking for complex, sour, and umami flavors) both act to produce the best environment for our immune system. Fermented food resembles exercise and practice; the mouth-touching system resembles information.

A similar sampling system is our love of gossip. We love to hear it, we love to spread it. Gossip spreads information about the dangers around us. Again, forewarned is forearmed.

I am in Tokyo (for a few more minutes), an admirably clean city. Public rest rooms, for example, are convenient, clean, and free. (Unlike New York, Los Angeles, San Francisco, Beijing . . . ) The practical point of this idea isn’t that there is something wrong with public health measures, it is that they can go too far.

• Comparing one elbow to the other. I have no idea what “clinical epidemiology” is. The level of self-deprecation is remarkable. From the BMJ Christmas issue.
• The value of cod liver oil. From the BMJ Christmas issue.
• More evidence for radiation hormesis (beneficial effects of small amounts of radiation).
• Evolutionary medicine reaches the BMJ. The word paleo does not appear.
• Medical journals: “information-laundering operations for drug companies”

Thanks to Robin Barooah and Mike Bowerman.