Packaged and processed foods, such as cakes, cookies, candies, chocolate, yogurt, and marshmallows, often contain unfamiliar animal ingredients, so may be a special concern for vegetarians due to the likelihood of such additions. Often, prior to purchase or consumption, vegetarians will scrutinize products for animal-derived ingredients. Vegetarians' feelings vary with regard to these ingredients. For example, while some vegetarians may be unaware of animal-derived rennet's role in the production of cheese, and may therefore unknowingly consume the product, other vegetarians may not take issue with its consumption.
A study by the Institute of Preventive and Clinical Medicine, and Institute of Physiological Chemistry looked at a group of 19 vegetarians (lacto-ovo) and used as a comparison a group of 19 omnivorous subjects recruited from the same region. The study found that this group of vegetarians (lacto-ovo) have a significantly higher amount of plasma carboxymethyllysine and advanced glycation endproducts (AGEs) compared to this group of non-vegetarians. Carboxymethyllysine is a glycation product which represents "a general marker of oxidative stress and long-term damage of proteins in aging, atherosclerosis and diabetes" and "[a]dvanced glycation end products (AGEs) may play an important adverse role in process of atherosclerosis, diabetes, aging and chronic renal failure".