Umami's not what you think it is. It's translated as "savoriness", but that's usually misinterpreted as a kind of general descriptor, the way food could be called "filling" or "chewy". It's also got a sense of being this subtle and higher-order property of good cooking, brought to us from the mysterious East.
Umami is a molecule. Well, actually a class of molecules that hit mGluR1 receptors (among others) in your mouth so that you get a meaty, savory taste. And it's not only appreciated by the discerning Japanese, but also by the somewhat less discerning hamsters. It’s a basic taste in the same way the other four are: The particular ingredient has been identified in food and the taste receptor has been identified in your mouth. Some don't believe in umami, but you still experience it unless you are missing the receptors for some reason, which would constitute a minor disability.
The most significant umami compounds are glutamates, which are the salts of glutamic acid, and in practically everything you enjoy as savory. Most cultures have created a glutamate-rich cooking ingredient that seems absolutely disgusting without an additional “this has glutamates” explanation. These include decomposing fish (anchovies, Worcestershire sauce, fish sauce), decomposing beans (soy sauce, miso), decomposing milk (cheese), and leftover beer-goo.
The way to conceptualize glutamates is to think of a culture that never isolated salt as a cooking ingredient. Salt is straightforward to isolate from seawater or to mine directly, but one could imagine a culture that loves foods such as olives, chips, pickles, and caviar without ever realizing what they really love is salt. Eventually, through trial and error, this culture ends up adding these sorts of ingredients to its savory dishes without ever recognizing the underlying principle.
This is roughly the state of the average Westerner in regards to umami, which results in the strange situation that Western cuisine is to Eastern medicine as Eastern cuisine is to Western medicine. Western medicine identifies the anatomical structure in the body, identifies the compounds which affect that structure, then dose the isolated compound directly to achieve a physiological effect. Eastern medicine has various substantiated or unsubstantiated theories on the physiological effect, and to the extent it has succeeded, it has been through trial and error without a physical understanding of the structures or mechanics.
Many of us are adding foods like Parmesan cheese, anchovies, stock, and tomatoes to food because they improve the taste, without realizing what we’re doing is adding glutamates. More aware chefs and consumers get an intuitive understanding of the principles, though often with some extraneous quirks.
A final more bizarre twist on this metaphor is that although it's added to your favorite processed foods and present in every popular dish, it’s still commonly believed 1) Umami is squishy and 2) Glutamates are bad for you, specifically monosodium glutamate aka MSG.
The proof that umami is concrete is that MSG is in so many megacorp junk foods despite its reputation. It’s typically listed as “monosodium glutamate” in the US, flavor enhancer E621 in Europe, or sometimes simply “natural flavor” if glutamic acid is used directly. This is not to mention numerous related compounds that are used to either avoid the red flag of “MSG” or ensure it appears far down the ingredient list. For a long time, I thought MSG was a food additive more like "Red 40", that it had some obscure food-science use and junk food companies were either too lazy or callous to replace it. It turns out it's more like salt. Good luck taking that out of your Cheetos.
Regarding its safety, you’re probably already eating MSG and you were fine. I know this because blinded studies show that people do not have sensitivity from plausible doses, and from the basic fact that MSG is glutamic acid attached to a sodium ion. You aren’t allergic to sodium unless you’re claiming to be allergic to salt, in which case you have bigger problems than umami. You are probably also not claiming to be allergic to glutamic acid as it’s an amino acid used by nearly all living beings and your body is synthesizing it at this very moment. It’s two bits you aren’t allergic to, which breaks into these bits when dissolved in water, which is to say immediately upon ingestion. That's not to say that because you're not allergic you couldn't be affected by large doses (see: salt), only that sensitivity to typical doses is unlikely.
Why do we even have glutamate receptors though? It must be something important enough that our tongues have evolved the sophisticated chemical machinery to identify a specific class of compounds amongst the thousands we ingest. It’s one of only 5 basic tastes. This sensitivity is even more remarkable considering that our sour taste broadly registers pH and there are over 600 bitter-tasting compounds, so it’s more like salty and sweet which are sensitive to a small class of desirable nutrients.
The best explanation seems to be that it’s used as an analog for protein and amino acids more generally. The non-fermented food most associated with umami is simply broths and meat. Unsurprisingly, MSG is a good shortcut to meatiness, which leads me to my biggest takeaway:
Put MSG on stuff!
Or at the very least consider the glutamate content of your food and add accordingly. You can add glutamate-heavy condiments like tomato paste or soy sauce, but adding MSG is easier because you don't have to worry about integrating flavors or managing consistency. Aside from food just tasting better and fooling people that you know how to cook, you get two big benefits:
- You can use less salt, too much of which is probably bad for you.
- You can put it on meat substitutes, whereby the performance ceiling goes from “that could pass for a real burger” to “damn that was good, I will now crave this instead of cheeseburgers”.
I ate meat daily for most of my life, and generally still want to. Having a meat substitute go from something that kinda scratched an itch to becoming a thing I actively craved has made phasing out meat feel like way less of a sacrifice. It's rare that a food additive can make my life that much easier.
So if you like it you should put some MSG on it. 
Also mammals in general. However, I wanted to find the funniest example and Google Scholar did not disappoint. ↩︎
“Desirable nutrients” is a context-dependent term of course. ↩︎
Why doesn’t Beyond Burger just put MSG on it themselves? The PR implications are likely prohibitive. New Age sensibilities are killing animals, you heard it here first. ↩︎