In a clever series called 10 Mysteries of You: Ten things we don’t understand about humans in New Scientist, Australian science writer Emma Young includes some obvious ones (blushing, altruism, dreams, art) but ends her list with a surprise: nose-picking. This had not occurred to me:

It is possible that ingesting nasal detritus might help build a healthy immune response – after all, researchers investigating the hygiene hypothesis have built a large body of evidence indicating that lack of exposure to infectious agents can increase one’s susceptibility to allergic diseases.

This seems to be Young’s idea rather than that of the scientist she spoke to. She has her hygiene hypothesis stuff wrong. The original hygiene hypothesis was indeed that lack of exposure to infectious agents can increase allergies — but the data later collected did not support this. More infections in childhood did not correlate with less allergy. What did seem to help was exposure to dirt. Apparently the dirt was helpful whether or not it was infectious (= contained something that could make you sick). The nose-picking data (kids pick their nose a lot and sometimes eat the stuff) does make sense given my umami hypothesis, which says that exposure to bacteria is good for us. You couldn’t get sick from eating what comes out of your nose but as it leaves your nose foreign bacteria grow on it; so eating your snot is a way to introduce foreign bacteria into your digestive system. Which the umami hypothesis says is needed for health.

Do kids who eat more fermented food eat less snot? As I posted earlier, since I started eating lots of fermented food, my desire for fancy restaurant food has gone way down.

Thanks to JR Minkel.

In an article in Slate about restrictive diets, Daniel Engber noted that

Celiac patients have almost twice the normal risk of cancer, and one-third of them suffer from another autoimmune disease, like Type 1 diabetes, lupus, or multiple sclerosis.

Does celiac disease cause cancer, Type 1 diabetes, lupus, and multiple sclerosis? Not very plausible. Does cancer cause celiac disease? Does lupus cause celiac disease? Not very plausible. Much more plausible is that all five have a common cause. I believe that common cause is a malfunctioning immune system due to not enough bacteria in the diet (the umami hypothesis).

More (May 2012). I now think that all these diseases are due to wheat molecules leaking into the blood and setting off an immune reaction that attacks parts of the body (because the wheat molecule resembles those molecules). The leaky gut that allows wheat molecules to enter the blood is caused by lack of bacteria in the diet.

Here’s a summary of a study that just appeared in Pediatrics:

More than 300 children between three and five years of age were randomly assigned to receive three different milk formulations: plain milk, milk plus the bacterium Lactobacillus acidophilus, or milk with Lactobacillus plus the bacterium Bifodobacterium animalis.

The group that just received Lactobacillus were half as likely to develop a cold and a fever. They also had fewer coughs and runny noses. Those that got both strains of probiotics had 72 percent fewer fevers. They were also less likely to come down with a cough or runny nose. If they did get sick, they got better significantly sooner. They also missed fewer days of daycare.

Here’s the abstract of that study:

OBJECTIVE: Probiotic consumption effects on cold and influenza-like symptom incidence and duration were evaluated in healthy children during the winter season.

METHODS: In this double-blind, placebo-controlled study, 326 eligible children (3—5 years of age) were assigned randomly to receive placebo (N = 104), Lactobacillus acidophilus NCFM (N = 110), or L acidophilus NCFM in combination with Bifidobacterium animalis subsp lactis Bi-07 (N = 112). Children were treated twice daily for 6 months.

RESULTS: Relative to the placebo group, single and combination probiotics reduced fever incidence by 53.0% (P = .0085) and 72.7% (P = .0009), coughing incidence by 41.4% (P = .027) and 62.1% (P = .005), and rhinorrhea incidence by 28.2% (P = .68) and 58.8% (P = .03), respectively. Fever, coughing, and rhinorrhea duration was decreased significantly, relative to placebo, by 32% (single strain; P = .0023) and 48% (strain combination; P < .001). Antibiotic use incidence was reduced, relative to placebo, by 68.4% (single strain; P = .0002) and 84.2% (strain combination; P < .0001). Subjects receiving probiotic products had significant reductions in days absent from group child care, by 31.8% (single strain; P = .002) and 27.7% (strain combination; P < .001), compared with subjects receiving placebo treatment.

The probiotics were given as pills. Such large safe improvements are signs of a nutritional deficiency being remedied. It would be very hard to produce a drug that worked as well.

Thanks to Tom George.

Bacteria-free mice have malfunctioning digestive systems and immune systems. Sarkis Mazmanian, an assistant professor at Caltech, has found that as little as one bacterial-surface molecule can make their immune systems work much better. Exposure to this molecule also protects the mice against a bacterium that would otherwise cause a mouse model of irritable bowel syndrome.

So far, so good: More evidence that we need bacteria for our digestive and immune systems to work properly. But then things get murky:

The Human Microbiome Project, an undertaking funded by the National Institutes of Health (NIH) to sequence the microbiota from hundreds of humans, has challenged itself with determining the relative quantities of all bacteria present in the human gut. With a known baseline of the bacteria present in healthy individuals, it will be much easier to understand which bacteria might be missing in diseased patients.

How we will find “healthy individuals”? I believe that almost everyone in America eats too little bacteria and has suboptimal health. Mazarian continues:

With a known baseline of the bacteria present in healthy individuals, it will be much easier to understand which bacteria might be missing in diseased patients. Hopefully, the Human Microbiome Project will lead to the discovery of other beneficial bacteria [in addition to the bacteria that Mazarian is studying].

“Much easier”? The bacteria that people need to be healthy must have been abundant in our environment long ago. We got vast amounts of bacteria from what we ate — bacteria that grew on food. To test the idea that these bacteria are beneficial you merely need to feed people bacteria-rich food (such as fermented food) and see if their health improves. This has been done hundreds of times, with highly positive results.