SPAM (which means "spiced ham") is a canned meat product invented in the United States in 1937. It was widely used as a food source during the second world war, both for soldiers and for civilians experiencing food shortages due to a reduced pool of agricultural labor. The ubiquitousness of SPAM as a food staple in the United Kingdom (a nation which had notable food shortages during the war due to its dependence upon agriculture) is parodied in the famous Monty Python sketch portraying a cafe that serves SPAM in every one of its menu offerings.
Like many smoked or processed meat products, SPAM contains nitrites as preservatives, and these have been implicated in a number of health issues when consumed in excess. Nitrites and nitrates can form nitrosamines, cells which have been shown to cause cancer in laboratory animals. The addition of ascorbic acid to foods containing nitrites is believed to help prevent the formation of nitrosamines in the body. Cooking meat containing nitrites (such as bacon or SPAM) at high temperatures may also form nitrosamines, so these products should be cooked slowly at low temperatures.