Dashi stock granules, Ajinomoto, MSG and health considerations
Seamaiden, who has a lovely gluten-free blog called Book of Yum, asked in the comments here whether Ajinomoto is gluten-free. Since I know that a lot of people become interested in rice-centric Asian cuisines, including Japanese, because of the wide variety of wheat-free dishes, I thought I'd post some of my findings here about Ajinomoto and dashi stock granules rather than bury them in the comments.
Monosodium glutamate or MSG is a concentrated and manufactured form of umami. It is a flavor enhancer with a lot of controversy. I won't get into that at the moment, since reactions to MSG really vary widely depending on the individual. The reality is that MSG is present in many manufactured food products.
Now specifically about Ajinomoto, the white granulated product that is synonymous with MSG: According to the official Japanese Ajinomoto company site, it is currently made by "fermenting the sugar extracted from sugar canes or corn, tapioca starch and other ingredients". That doesn't mean of course that MSG manufactured by other companies are made the same way. They also state that when the company was founded, they used to make MSG from wheat gluten, and later moved on to extraction from soy beans.
Ajinomoto is also a major manufacturer of dashi stock granules (their product name is Hondashi). On the Hondashi page they emphasize that they make Hondashi from real bonito (this is why dashi stock granules are not vegetarian).
Food allergies are just as hot a topic in Japan as they are in the rest of the world, especially children with allergies. Unlike in the English speaking parts of the world where allergies seem to be defined more granularly, most environmentally caused allergies are called by the general name atopii (アトピー), which is derived from the term atopic syndrome. Generally the current commonly held belief amongst people affected by atopii, especially mothers with allergic children, is to avoid all food additives, including Ajinomoto/MSG (called kagaku choumiryou, meaning "chemical food flavoring") and dashi stock granules. Whether this has concrete scientific backing is beyond the scope of this site, but it might be something to consider if you're affected by food-related allergies. (Anyone who's been to Japan knows that there are a positively staggering array of skillfully packaged and marketed manufactured/pre-packed products loaded with chemicals, additives, etc. there. Instant ramen is just one of millions of probably-bad-for-you products.)
As for myself, I haven't had Ajinomoto in my kitchen for a very long time. I can't even remember the last time I bought it. I do however use other flavor enhancers on occasion, such as dashi stock granules and soup stock cubes. Fortunately no one I have to cook for regularly (including myself) has a known intolerance for these foods. I do much prefer to make dashi stock from real bonito flakes and kombu seaweed, since it's relatively easy to do so. (Compare the procedure for making a bonito-kombu stock to making say, a real beef stock from bones and such...the latter is considerably more complicated and messy.)
The good news as far as Japanese cooking is concerned is that many if not most, Japanese dishes rely on a boost of umami, but adding this is quite simple since many natural or naturally produced ingredients that are used in everyday Japanese cooking are loaded with umami: bonito flakes, kombu and other seaweeds, dried shiitake, dried fish (niboshi) or dried fish powder; miso; soy sauce; and so on. So, when in doubt you may want to rely on the natural umami ingredients.