From my point of view, let me say that Japanese-Americans weren't the only ones displaced by the war. Hundreds of Alaska Natives were taken from the Aleutian Islands by both the United States and Japan. For those taken by the Japanese, it was a true internment. For those transported to Southeast Alaska, it was more a refugee situation. Still, G. Edward White called it the Lost Internment, and I think that fits. The Natives could move (and did) to take jobs in Juneau and other places in Southeast Alaska. Still, conditions were hard, and several of the 86 people landed at Killisnoo died during the war. I intend to visit the site of the camp on Saturday.
Let me return to your original question. Much has been written about this subject. You may want to turn to the Japanese-American National Museum, which has an extraordinary letters collection. If you're a visually oriented person, you may want to see the documentary "Children of the Camps," which follows the lives of six interned children.
Conditions in the camps varied greatly. The War Relocation Authority (WRA) attempted to create camp communities that resembled normal communities to the greatest extent possible. Each of the 10 camps had schools and hospitals, a newspaper, some degree of democratic self-government and leisure activities as baseball leagues and movie showings. The WRA encouraged "loyal" camp residents to resettle in inland cities like Denver or Chicago, but many didn't take the offer -- they didn't trust it.
Here are a few letters from Louise Ogawa, who wrote from Poston War Relocation Camp in Arizona, which housed more than 17,000 people at its peak in 1943. Ogawa's letters were later turned into a book, and there are ample other writings as well.
While answering another question on US internment policy in WW2 a while ago, I was reading Personal Justice Denied, the final report produced by the Commission on Wartime Relocation and Internment of Civilians. It's a comprehensive review of the internment programme, and in large part a fairly damning indictment of the implementation of that programme.
Chapter 6 has a section on life in the camps (from p158, and particularly relevant from p162), which may be of interest to you. Some relevant excerpts on food/nutrition:
The [War Relocation Authority] walked a fine line in providing for evacuees' basic needs, on the one hand was their genuine sympathy for the excluded people. On the other was a well-founded apprehension that the press and the politicians would seek out and denounce any evidence that evacuees were being treated generously. WRA's compromise was to strive for a system that would provide a healthy but Spartan environment. They did not always succeed, and it was usually the evacuees who suffered when they failed. [p162]
[...]
Food quality and quantity varied among centers, generally improving in the later months as evacuees began to produce it themselves. The WRA's expressed policy was that evacuees were entitled to the same treatment as other American citizens: WRA was to provide an adequate diet; foods rationed to the public would be available to evacuees in the same quantities. The reality, however, was very different.
[...]
In January 1943, after accusations that the evacuees were being coddled, the WRA adopted new policies which showed that their fear of adverse publicity had overcome any humanitarian impulse. "At no time would evacuees' food have higher specifications than or exceed in quantity what the civil population may obtain in the open market." Centers were ordered to submit their planned menus for each 30-day period to Washington for advance approval to make sure that the public was adequately informed of WRA feeding policies. Perhaps the best that can be said of the meal system is that no-one starved.
The general tone of the report is that the internees existed in something of a grey area: they were being detained by the state and deprived of their rights in extraordinary circumstances, and in a climate of mistrust and suspicion. There's an inherent conflict there; one that's difficult to reconcile. They weren't conventional judicial prisoners; they weren't prisoners of war. They were (in large part) American citizens who had committed no crime but were being detained without legal recourse. So the question of the conditions in which they could be held was complex — and only complicated further by public opinion and political expediency.
There are examples of abuse or mistreatment of prisoners by camp guards — tensions between those two groups did arise (see pp174-180) — and the general living conditions in the camps were poor. It was certainly not a comfortable detention — and one not easily justifiable in legal or constitutional terms. But in general, the internment camps were more comparable to allied prisoner-of-war camps than concentration camps; the level of humanity afforded the detainees was completely different, and there wasn't the same kind of systemic/systematic abuse of prisoners by the camp authorities that you saw in, for example, the German camps.
Is "concentration camp" accepted terminology? That's a very loaded phrase, usually only reserved for Nazi death camps.
I hope this doesn't count as anecdotal evidence, but if it is, I understand.
My grandmother essentially grew up in an internment camp(Poston). She's an artist and has a book of watercolors that she did about her memories of camp. This is a link to the gallery of the pictures and her commentary on them. It may not provide a full picture of the conditions, but you can get a general idea. However, keep in mind that this is just one camp of many.
They weren't really prisoners in the way you may think of people in jail(they were still prisoners though). The camp itself was more like a small town. The men old enough to work would often have jobs(my great grandfather worked as a janitor in the camp, and my great uncle was a fire fighter). They had general stores in the camps where you could buy necessities, though some of those were also given regularly(particularly in the beginning when they were still getting everything all set up).