Note: The goal of this post is to provide simple, practical advice for my friends and family regarding glycine supplementation. If you want to dive in to more detailed research regarding the benefits of glycine---and I recommend you do!---then you can start by perusing the links at the bottom of this post.
Methionine is an essential amino acid, prevalent in meats and animal foods like eggs and milk. Excess methionine is harmful to humans, and leads to all sorts of problems, causing inflammation and probably contributing to cancer, heart disease, early death, etc. It's probably a good idea to think of excess methionine as the #1 endogenous toxin in the human body. There are two basic strategies for dealing with excess methionine:
(1) Consume less methoinine. For most people this would mean eating a vegetarian or mostly vegetarian diet, because if you eat less meat/dairy you'll usually end up consuming less methionine. This can be an effective strategy, but (a) it can be difficult for some people to adhere to this diet, and (b) there are other potential nutritional downsides to a mostly-vegetarian diet, and with restrictive diets in general, which I won't discuss here.
(2) Consume more glycine. Glycine is different amino acid that basically clears excess methionine out of your system. Giving glycine supplements to rodents increases their lifespan and significantly reduces their susceptibility to disease. Basically, glycine supplementation is amazing and helps just about everything (surprisingly, it even seems to reduce and/or eliminate the side effects of excess sugar consumption).
The second strategy is probably the better one, and it's certainly the easiest to implement. Sources I've read indicate that supplementing 5-8 grams of glycine daily is probably a good idea for average adult Americans (more than 8 grams would probably be superfluous). I aim for 5 grams, personally. Here are a few ways to get glycine:
(a) Eat gelatin. We're talking a LOT of beef gelatin here, because gelatin is only about 20% glycine. So if you're aiming to supplement 5 grams of glycine daily that means eating ~25 grams of gelatin. That's a little over 2 Tbsp. That's a lot of jello. But that's doable. There are also cold-water-soluble forms of gelatin that you can dissolve in juice. I estimate this gelatin strategy would cost a minimum of $0.40 daily if you're only buying cheap gelatin in bulk 5 lbs bags, and a maximum of $1.13 daily if you're only buying cold-soluble-gelatin on Amazon, and somewhere between if you're doing a combination. Personally, that's too expensive for my budget, and even if I could afford it I probably wouldn't want to eat that much gelatin.
(b) Eat glycine powder. Pretty simple, right? You can buy powdered glycine on Amazon, and it's surprisingly cheap. At 5 grams a day, it would cost $0.15 a day. This is the cheapest and easiest option I'm aware of, and it's what I'm doing personally. It tastes pretty good ...basically just sweet. We add lemon juice and water and make a lemonade drink out of it. (The trick is to avoid diluting it too much, otherwise the sweet taste goes away and it imparts a bitter off taste.)
(c) Take glycine pills. You could either buy pre-made pills, or make your own pills using empty size "000" capsules. Pre-made pills will cost you $0.36 a day, whereas homemade pills would cost approximately $0.20 a day.