Old Dame Dob

[shkrobius]

My journal enters the 2011 season, which is likely to be its last season. By tradition, the first post of the season is on a nursery rhyme.

Jack and Jill went up the hill

Comments

[poltorazhyda]

Here's a question I came up with: why are children picky eaters compared to adults?

[shkrobius]

When and where I was a kid, there were no picky eaters.

[poltorazhyda]

Yeah, when I was a kid, we had to walk 5 miles to school and back, uphill both ways. Still, in a non-scarcity environment, kids are more picky than adults.

[shkrobius]

Why do you say that? I mean, suppose you are a picky adult. As an adult, you can eat whatever you want: you can live on chocolate bars, alfa-alfa, whatever. But if you are a picky child, then everyone will be telling you that you are picky, you will be denied chocolate bars, etc. I do not think kids are any more picky in their food than the adults, but they are constantly being corrected while the adults are not. Another difference is that the kids would not hide their food preferences.

[poltorazhyda]

Based on empirical observation. Very few adults choose to live on chocolate bars, but a lot complain about their kids being picky.

I used to hate onions and cabbage with a passion, to the point of nausea. While I still dislike them, I can eat them now. My father told me that he had the same issue and it changed with age. I suspect that there is some chemical reason involved.

Supposedly, even the Khoisan hunter-gatherers only eat a fraction of the edible plants available in their Kalahari habitat, due to taste preferences; I would guess that this "you will eat what you are given, and you will eat all of it!" mindset comes from industrialized society and its conveyor-belt approach.

[shkrobius]

If it is cooked onions and cabbages, there are indeed chemical reasons. Cooked cabbage smells/tastes of dialkylsulfides produced from methionine, and cooked onions produce similar S-containing molecules. Fish and beer could be unpleasant for the same reason. The reason adults are more tolerant, if I remember it correctly (that is what I was told twenty years ago), is that as we get older, there are more anaerobic microbes living on the tongue that produce sulfur compounds of very similar structure. Basically, this is gradual development of halitosis. It may not be dog breath, but it is sufficient for the taste and smell receptors become more tolerant to organic sulfides, thiols, etc.

If your question is specifically about onions, cabbages, and other VSC-rich foods, there are indeed reasons why adults are more tolerant than kids.

[poltorazhyda]

Interesting. What's the evolutionary advantage of having more anaerobic microbes in the mouth as we get older?

[shkrobius]

There is no advantage (to you). Mouth bacteria gradually get the upper hand as you get older, that's all. Eg, teeth and gums begin to rot, there is inflammation, bleeding, it feeds more bacteria, etc. Anaerobic bacteria can hide in pockets and break down tissue and saliva proteins. There is little oxygen below the gum line.

If you mean why the bacteria in the mouth are mainly anaerobic, not all of them are (1/4 are aerobic). There is not too much oxygen when you sleep which gives the anaerobes periodic advantage (hence bad breath in the morning). Also bacteria need to hide deeply in the crevasses or make dense biofilm to protect themselves against lysozymes in the saliva. This limits oxygen diffusion. There could be other reasons I do not know about.

The short answer is that gradual destruction of teeth and gums, weakening of immunity, etc. work for the bacterial advantage while anaerobic proteolysis produces S-containing molecules; the receptors respond to this fouling by readjustment. Not a pretty subject, aging.

[poltorazhyda]

Why hasn't our body developed a defense against this? I mean, even hunter-gatherers routinely live into middle and old age. It seems like something as simple as circulating air through the mouth periodically during sleep could have a high return-on-investment.

[shkrobius]

Perhaps bad breath was not their biggest problem. Also, tooth decay was slower because people ate coarse food with little amount of sugars in it; perhaps halitosis developed around the time when other wear and tear was a greater burden, past the peak of the reproductive age.

[poltorazhyda]

The paleo diet guys claim that non-infectious chronic diseases like this kind of tooth decay (and diabetes, etc.,) were very rare before the modern diet became common; they say that even in the Neolithic, wheat had much more protein and less carbohydrates than that of today. Don't know how valid their logic is; guess we'll find out in 20 years when they get older, whether they have lower non-infectious chronic disease rates than their cohort.

I guess the corollary is that back in the day, people would have avoided cooked onions, cabbage, etc. throughout their lives?

[shkrobius]

Cabbages are very recent; even in the early antiquity "cabbages" were, actually, kyle. Boiling requires pottery, so it is Neolithic 3, which is 6500 BC in the Levant, where kyle and onions were domesticated. Eating boiled cabbages and onions is the relatively recent thing.

I do not know what was the original attraction of raw spices, especially condiments like radishes or mustard. It used to be said that condiments covered rancid meat, now they say it is antibacterial action. I had an idea that it could've worked as an equalizer: everyone eating onions, garlic, radishes, smells the same way. Maybe it was masking bad breath, putting the older folk back into the sex game. I am speculating here.

[egork]

Talking about bad breath in the morning, I believe it to have more correlation to the evening meal than to what type of bacteria one has. Just because one would brush the teeth every night, but not have bad breath every morning. If the mouth is clean to the same extent every night, why the result is different one morning from another?

[shkrobius]

No, this is, actually, correct: the main reason it smells worse in the morning is that the mouth is not well ventilated during the night. Brushing your teeth has little effect on the bacteria: the way brushing works is that fluoride in the toothpaste is included into the tooth enamel making it more difficult for the bacteria to destroy the enamel by secretion of acid. Otherwise, it has almost no effect. You remove some residues etc. but there is plenty of protein in the saliva and the tissues to feed the bugs. Some bad odor comes from the stomach (the amines, for example) and this is what might make it better or worse on different days. Halitosis is specifically volatile S-compounds from the mouth; bad breath is a more general problem. Most people do not clean their tongue from bacterial films, while most of the anaerobic bacteria are at back of the tongue. Said that, food does have effect on the microbial activity. For example, aerobic bacteria turn carbohydrates into lactic acid, and it suppresses the anaerobic activity. The problem