Salt, We Misjudged You

So, MSG may or may not be bad by itself, but the highly processed empty calories that it hangs out with, definitely bad. Bet you can't eat just one? I don't take that bet anymore, I lose too often.

I don't think there's any doubt about this. Compared to evolutionary rates, the typical diet in the west has changed at lightning pace from just a few decades ago, meaning our bodies and taste buds are behind the curve. We need willpower and common sense to have a healthy diet, rather than raw survival instincts.

Unfortunately what's driving change in our diet is the demand for companies to serve food with high profit margins and low cost raw materials (e.g. high-fructose corn syrup). Capitalism is great for providing us with cheaper clothes and ever-cheaper computing power, but providing cheaper food means providing crappier food. There's no Moore's Law for food.

I think it was here on HN I read about studies done in remote communities (possibly some remote whaling community) that had recently become westerised, and the diet quickly shifted to one more similar to a typical American diet. Within 5-10 years (or a relatively short time frame, can't remember exactly) obesity and type-II diabetes rates exploded.

Another interesting story was reports from surgeons who operated on injured Afghan fighters from the current conflict. Normally when operating on westerners, you expect a certain amount of yellowish fatty tissue surrounding the major internal organs. This wasn't present on Afghan locals, which surprised the surgeons who were so used to seeing it on western patients and pretty much assumed it was normal up till that point. The difference was down to diet.

My favorite example is Vitamin B12, mostly because I learned the story when I reduced my meat consumption to about once a month. So there's this family of massive molecules containing the metal cobalt which we can't make on our own because we're not adapted to eat cobalt, and they're all called "Vitamin B12". It helps in the last step of making the protein building-block called methionine; if you get malnourished in this way your body just basically fills up with "almost finished" methionine which is useless and might even be poisonous. There can also be a slight risk of nerve damage although as I understand it we don't actually understand why the hell that would be.

The biggest cause of malnutrition in this sense is simply being old -- you can't absorb Vitamin B12 so well in the first place because it is huge and weird, and old people have even more trouble either because their gut is slowly dying or because they're infected with H. pylori, which is a safe bacteria more than 80% of the time and might even be important for a well-functioning stomach, but might sometimes cause a chronic tummy-bug.

Okay, so that's the problem, but what do we know about how much of the B12s we need and get? We know very little. The US Recommended Daily Allowance of B12s is 2.4 μg, but the US Daily Value for B12 is 6.0 μg. How much do you get in your food? You get almost none from vegetables, and vegans are basically all ipso facto suffering from B12 deficiency unless they take supplements or eat enriched cereal -- but most of them are quite healthy and see no problems from it. As for vegetarians like (almost-) me, the exact range for milk and eggs to get to this limit is imprecise because the limit itself varies by a factor of 3, so you might need to eat three eggs per day or else ten; so you might need to drink two cups of milk per day or else five, to live up to those numbers. So in theory there are lots of vegetarians also who come in at half or one-third their daily requirement, and never notice anything. Meanwhile there are people over 60 who eat plenty of meat but are starting to feel the effects anyway.

We actually don't even know how well you absorb it. A USDA researcher named Lindsay Allen did a 2011 study where she marked Vitamin B12 in eggs so that she could detect it, and then fed those eggs to 10 people. She found that the body absorbed 50% of a 1.5 μg dosage but only 20% of a 2.6 μg dosage. Let me repeat that. She found that, in absolute value terms, eating more B12 led to less of it being absorbed, 0.75 μg versus 0.5 μg. It's probably not statistically significant with 10 people, but still. We don't even know that eating more leads to you absorbing more of it. (I also wonder whether RDAs are "amount absorbed" while DVs are "amount eaten", as this is pretty much never reported, but I will assume that they aren't crazy and that it's always "amount eaten.")

I wouldn't use the scare-quotes around "science" when talking about nutrition science, as I think there is potential for real research here and I think people do indeed do it -- but it's a lot of work before we have a firm understanding, and most of that work hasn't been done yet, and yet you hear these confident conclusions. I would just like to hear people publish standards in the form, "you might need this much, or that much, we don't really know."

The engineer in me craves error bars. Where are the error bars?