Talking Turkey

Nutrition comes with myths and magic. The scientific realities of tryptophan

| 13 Dec 2019 | 01:19

Remember that yummy roasted Thanksgiving turkey? Remember falling asleep after finishing the feast? Get ready for a re-run because, as the song says, “Everybody knows a turkey and some mistletoe, help to make the season bright.”

Nutrition is a very new science. The term vitamin (from the Latin word vita meaning life) wasn’t even invented until 1912. Like any other new thing, nutrition comes with myths and magic including the essential amino acid l-tryptophan.

The science community has known about tryptophan since 1901 when British chemist Sir Frederick Gowland Hopkins isolated it from the milk protein casein, a discovery for which he was awarded the Nobel Prize in chemistry in 1929. No wonder: Your body uses the tryptophan it gets from food to make the B vitamin niacin and the really magic chemical compound serotonin which influences mood, helps you relax, and is integral to the creation of melatonin, the hormone that helps to regulate your circadian rhythm, that is, your sleep and wake cycles.

The general public – you and me – probably got the message 96 years later on November 6, 1997, when NBC-TV aired the 162nd episode of Seinfeld in which Jerry and George fed a friend a dinner of turkey – tryptophan! – to lull her to sleep so they could play with her antique toys.

The guys were right to assume that turkey is a good source of l-tryptophan. But does turkey alone really put you to sleep? Probably not. Chicken has exactly as much tryptophan per serving as turkey; a bunch of other protein foods have more. More to the point, on its own tryptophan is a pretty week puppy. To make its way through digestion, into your bloodstream, and on to your brain, it needs a carb assist. As the National Sleep Foundation explains, “That’s why carbohydrate-heavy meals can make you drowsy, and why the best bedtime snack is one that contains both a carbohydrate and protein, such as cereal with milk.”

Sudden Grogginess

So, if eating turkey isn't exactly the same as popping a sleeping pill, why the sudden grogginess as soon as our holiday feast is over? “It’s not all about the tryptophan,” says Bonnie Taub-Dix, RDN, creator of and author of "Read It Before You Eat It." "It’s also about spending lots of time enjoying happy hour, sitting for long periods of time, and, yes, those desserts at the end of the meal!”

Libby Mills, a national spokesperson for the Academy of Nutrition and Dietetics has a sensible work-around: Less sleepy desserts. First, make it mini (smaller portions). Second, make it lighter (applesauce instead of fats in muffins and quick breads). Third, make it frozen (fruit juice pops instead of ice cream). Finally, make it sweet but use less sugar (one tablespoon less sugar in baking with maybe a substitute spoon of moistening fruit puree instead).

P.S. In 2018, writing in The International Journal of Tryptophan Research, USDA research chemist Mendel Friedman suggested that because it plays a role in making good chemicals in our bodies, the tryptophan we get from food “may have the potential to contribute to the therapy of autism, cardiovascular disease, cognitive function, chronic kidney disease, depression, inflammatory bowel disease, multiple sclerosis, sleep, social function, and microbial infections.”

Add some carbs, and that’s enough to give you sweet dreams.

In 2002, the U.S. Institute of Medicine set the recommended daily intake for tryptophan at 4mg per kg of body weight/1.8mg per lb.
Example: A person weighing 68 kg/150 lb should consume around 272 mg of tryptophan per day.
Food Tryptophan (mg in 100g/3.5 oz serving)
Soybeans (roasted) 575
Parmesan cheese 560
Cheddar Cheese 320
Pork chop 250
Turkey 240
Chicken 240
Beef 230
Salmon 220
Egg (1) 170
Unsweetened chocolate 130
Milk (whole) 75
(nonfat) 56
(low-fat) 55