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2011_06_30:14: A tryptophan and rice myth
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"Serotonin is synthesized from tryptophan in the presence of adequate vitamins B1, B3, B6, and folic acid. The best food sources of tryptophan include brown rice, cottage cheese, meat, peanuts, and sesame seeds." Source: http://www.fi.edu/learn/brain/proteins.html
Why would anyone call brown rice a "best food source of tryptophan"?
I stumbled on this false-oid this morning. I was testing my nutrition program, one of the features of which is to take the name of a nutrient and give back a list of every food that contains it, along with the amount of the nutrient that is contained in a given gram weight of the food. The nutrient that I happened to use for the testing was tryptophan, an essential amino acid.
Essential amino acids are those that can't be synthesized from other things by the human body. We have to get them in our food. If we don't get them in our food, we tear down our own muscles in order to get them for daily processes. We have no choice about this whatsoever. It's not a political decision. You can't decide that, since you want to be a vegan, you don't need tryptophan (or muscle, or neurotransmitters); rather, you have to find a way to get tryptophan without eating meat or milk, end of debate. Since we make the neurotransmitter serotonin from tryptophan, you'd better eat tryptophan in adequate quantities.
OK, let's do a search on tryptophan and see what we get. The top results are protein isolates. This isn't surprising. Amino acids are what proteins are made of, so if your food is pure protein, you'd expect it to have more of each amino acid than a food that has water and fat mixed in (like fresh roast beef) or that is mostly sugar and water (like a fresh apple). What *is* surprising is that turkey is not the next food on the list, after the protein isolates. This is surprising because it is common mythology that "everyone knows", that turkey is one of the best sources of tryptophan--except that it isn't.
Here's what we get on the list that my program produces, along with the ranking (out of about 8,000 foods) and the amount supplied in 100 grams of the food, skipping most of the weird foods like dried beluga meat and various soy protein isolates and dried egg whites, and skipping over duplicates (the cheeses are listed over and over with differences in single milligrams, for example):
grams in 100 grams of food
1.600 Stellar sea lion meat with fat 1 (1 out of 8,000)
1.116 soy protein isolate 5
0.929 dried spirulina 10
0.762 raw (dried) winged beans 18
0.721 dried chia seeds 24
0.625 cooked pork pancreas 32
0.618 cooked whelks 33
0.603 part skim mozzarella cheese
0.591 dried soy beans 37
0.569 shelled roasted pumpkin seeds 44
0.560 shredded parmesan cheese 45
0.436 wild rabbit meat 69
0.415 domestic lamb shoulder 72
0.410 pork shoulder 74
0.405 beef top round 78
By this time, if you're like me, you are getting very impatient to see something justifying the claim that brown rice is a "best source of tryptophan". You may even be wondering why you don't see turkey yet. Where is it? Scanning down the list and skipping other interesting meats like elk and goat and various cuts of ground beef and other cheeses like gruyere, we finally see some poultry at rank 81 out of 8,000:
0.403 goose roasted 81
0.400 duckling leg meat 86
0.393 sesame seeds 98
0.390 fried chicken 101
0.375 cooked fish eggs 122
0.350 TURKEY WING MEAT ONLY 190
Finally! Ranking 190 out of 8,000, after a couple hundred other foods including all sorts of other animal flesh foods, most of which normal people could eat in 100 gram portions, we finally get turkey. But interestingly, turkey doesn't appear on the list again until #220:
0.343 turkey light meat 220
with all sorts of other meats and cheeses again taking higher rankings.
But, my question wasn't where turkey falls on this list; that was just a diversionary sub-myth about tryptophan. We were looking for rice. Where does rice appear on this list? We haven't seen that yet, but here's wheat berries (wheat berries are sort of like rice, before they have been ground up into flour), at ranking 1,513 out of 8,000:
0.195 hard red spring wheat berries 1513
Finally, we get rice at ranking 1723. But it's not brown rice, it's *wild* rice, before cooking:
0.179 wild rice raw
and another grain:
0.167 quinoa uncooked 1822
At this point my program gave up (a little bug I need to fix :). So I restarted, and this time chose to look for tryptophan ONLY in grains. Among grains and grain products like flours, it turns out that WHITE rice, NOT brown rice, comes in at ranking 73, and brown rice comes in at ranking 83:
0.110 white rice 73
0.101 brown rice 83
That's 73 and 83, respectively, among *grains*, not among all foods. In other words, EVEN AMONG GRAINS, rice is a *terrible* source of tryptophan. This just goes to support my contention, which I can't seem to get anyone to believe, that rice is one of the most worthless foods one can eat. As poorly as it does on the amino acids and protein ranking, it does even worse at supplying vitamins and minerals. Almost any grain that you randomly pick is going to be better for you. But nevermind that. The question was, what would make someone say that rice is one of the best sources of *anything* other than carbohydrates, let alone one of the best sources of tryptophan? You tell me.
Compare rice to vegetables. 100 grams of cooked spinach has the same amount of tryptophan as 100 grams of uncooked white rice. But spinach has tons of other nutrients as well, and isn't loaded with empty carbohydrates. If you're going to list rice as one of the best sources of tryptophan, why not list spinach?
0.101 spinach cooked
Exploring a little further just for the fun of it, I note that the top whole raw bean, kidney beans, has three times the amount of tryptophan as the same quantity of rice, and several other very common, tasty, much more nutritious legumes also easily outrank rice:
0.300 raw kidney beans
0.275 raw split peas
0.272 roasted spanish peanuts
0.254 raw lima beans
0.252 raw black turtle beans
0.242 boiled soy beans
This is the sort of information that my program ferrets out and lays bare. Do with it what you will. I apologize if I upset your worldview, but hopefully you'll start eating better on account of it, and this will make your brain work better due to the upsurge in serotonin. You're welcome! :)