In the past several decades, there has been considerable interest in lycopene-rich foods, particularly tomatoes and tomato products, in lowering a man’s risk of getting prostate cancer. In the previous AICR report, the strength of evidence for a benefit was viewed as “probable” for lycopene-rich foods, but in the latest round, the recommendation was lowered to “limited, no conclusion.”
To understand this change, it is important to examine the nature of the evidence used to reach the new conclusion. Most of the evidence is based on studies that record what men are eating, or measure blood lycopene levels, and then follow the men for any diagnosis of prostate cancer.
Then dietary or blood factors are linked to risk of cancer diagnosis. Statistical methods are used to account for other factors. Because these studies are examining associations, which may not necessarily be causal, other considerations such as biologic plausibility are taken into account in formulating the conclusions.