Summary of Research - Tomatoes / Lycopene and Disease Risk

2009 UPDATE

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 and now again in 2009 (cut off Oct 2009 for published original research). All qualified research for this review is in humans and from original journal communication. Previous versions included a review of the published science in cancer and cardiovascular disease (CVD) research. New to this update is a review of the published research in humans investigating the relationship between tomato, tomato products and lycopene on skin protection (Skin), bone health (Bone), cognitive function (Brain), and body weight management (BW). Cancer and CVD have been updated as well. The format of the summary report is described below. Results and study information from previous versions have been integrated. A total of 469 abstracts are included: Cancer, n=178; CVD, n=76; Skin, n=8; Bone, n=6; Brain, n=6; BW, n=7; Tomato intake and plasma/serum lycopene concentrations, n=28; Cancer risk reviews, n=39; Chronic disease reviews, n=10; and Special interest, n=111. Published research abstracts are organized into the following sections:

Website Site Map

Each disease/health-related section includes 4 subsections:

  • Dietary Lycopene and Disease Risk
  • Plasma/Serum Lycopene and Disease Risk
  • Lycopene Supplement and Disease Risk
  • Tomato/Tomato-based foods and Disease Risk

Stand alone sections include: Tomato intake and Plasma/Serum Lycopene, Tomato/Lycopene Reviews and Tomato/Lycopene special interest abstracts. For the purpose of this summary, only original research (in the first 7 categories), including subcategories are discussed in detail.

Special interest studies are those that were reviewed, are related to the topic area and considered of “interest” but do not specifically associate tomato or lycopene with a disease risk outcome in humans. These studies are generally older publications and focus on fruit and vegetable intake on disease risk or in the case of newer investigations focus on mechanism of action in in vivo animal or in vitro models. The summary of research database includes published work up to Oct 2009.

The review is based on abstracts of human studies. For greater detail and depth to this review, original articles and complete review of papers in their entirety is required. Despite the limitation, this review provides substantial information for identifying research gaps and opportunities for developing industry direction and research strategy.

Qualifying results

Research investigations were qualified by disease/health-related condition, study type, sample size and main result as reported in abstracts and confirmed as necessary by full article. Results were designated as (-), N, (+), (-)/N in tabular format. Each Table of results is accompanied by a brief summary of main findings.

Study type

  • RCT: Randomized Control Trial
  • Interv: Intervention, baseline control, no Pbo
  • PC: Prospective cohort
  • CC: Case-Control
  • CS: Cross Sectional
  • Eco: Ecological

Sample size classification

  • RCT/ n= based on total # of subjects
  • Interv/ n= based on total # of subjects
  • PC/ n= based on cases identified in population
  • CC/ n= based on number of cases studied (case-control ratios 1:1, 1:2 or 1:4)
  • CS/ n= based on total # of subjects

Result designations

  • (-) = Inverse relationship between dietary variable and disease risk or other specified endpoint.
  • N = Neutral relationship between dietary variable and disease risk or other specified endpoint.
  • (+) = Direct relationship between dietary variable and disease risk or other specified endpoint.
  • (-)/N = Studies that had multiple endpoints and were mixed in outcomes were designated a combination result.

    For all studies, except for those investigating a diet/serum lycopene relationship, the beneficial outcome is (-).

Summary of Research Findings

Three hundred and nine (n=309) human studies investigating the effects of tomato/tomato-based foods and or lycopene on many forms of cancer and cardiovascular disease, skin protection, bone metabolism, brain function and body weight management are referenced. The number of cancer- based research studies overwhelmingly exceeds that of cardiovascular-based investigations and far fewer publications are available for the association of tomato/tomato-based foods or lycopene and skin protection, bone metabolism, brain function and body weight management. Future work should consider balancing the knowledge-base and focus on the relevance of tomato/tomato-based foods on important risk factors of multiple diseases, such as, but not limited to, obesity, central adiposity, insulin resistance, diabetes, metabolic syndrome, oxidative stress and inflammation/immune function. Important considerations for future research should also consider building the knowledge base in skin protection, bone health, brain function and body weight management.