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In our review of literature on vitamin C supplementation and its effect on lifespan in different model organisms we found that some studies suggest an increase in lifespan , other studies failed to observe any beneficial effect of vitamin C on longevity and some studies even reported a decrease in lifespan following vitamin C supplementation .
 vitamin C, vitamin C, vitamin C
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 vitamin C, vitamin C, vitamin C