In July 2006, a research database was constructed to manage the most up-to-date research describing the diet-disease relationship for tomatoes, tomato products and lycopene. This database was updated in 2007, 2009 and now again in 2011 (cut off Oct 2011 for published original research).
Thirty-four (34) publications meeting criteria for this review were available. Data suggest a neutral relationship between dietary lycopene and risk for diabetes mellitus based on incidence of disease and risk factors, such as HgA1c, glucose, insulin. Plasma/serum lycopene concentrations and diabetes risk are mixed with both protective and neutral relationships reported in nearly equal ratio. Data are limited for lycopene supplementation (n=2 studies), but may suggest a beneficial effect for risk factor management in people with diabetes. Lycopene supplementation decreased oxidative stress and improved lipid status in people with diabetes. Similar findings were shown in studies feeding tomato/tomato products, including 1 study reporting improvements in HgA1c. Observational data on tomato intake are mixed with neutral, negative and positive relationships with diabetes/risk factors reported. Processed tomato products appear to be a favorable choice for potential benefits; although this observation is limited and requires additional research for clarity. Findings are based on effects of tomato/tomato products on glycation variables, lipids, oxidative stress and insulin.