The Longevity Project » Molecules

Tomatoes, tomato-based products, lycopene, and cancer: review of the epidemiologic literature

TLP — Tue, 03 Jul 2007 18:13:38 +0000

The epidemiologic literature in the English language regarding intake of tomatoes and tomato-based products and blood lycopene (a compound derived predominantly from tomatoes) level in relation to the risk of various cancers was reviewed. Among 72 studies identified, 57 reported inverse associations between tomato intake or blood lycopene level and the risk of cancer at a defined anatomic site; 35 of these inverse associations were statistically significant. No study indicated that higher tomato consumption or blood lycopene level statistically significantly increased the risk of cancer at any of the investigated sites. About half of the relative risks for comparisons of high with low intakes or levels for tomatoes or lycopene were approximately 0.6 or lower. The evidence for a benefit was strongest for cancers of the prostate, lung, and stomach. Data were also suggestive of a benefit for cancers of the pancreas, colon and rectum, esophagus, oral cavity, breast, and cervix. Because the data are from observational studies, a cause-effect relationship cannot be established definitively. However, the consistency of the results across numerous studies in diverse populations, for case-control and prospective studies, and for dietary-based and blood-based investigations argues against bias or confounding as the explanation for these findings. Lycopene may account for or contribute to these benefits, but this possibility is not yet proven and requires further study. Numerous other potentially beneficial compounds are present in tomatoes, and, conceivably, complex interactions among multiple components may contribute to the anticancer properties of tomatoes. The consistently lower risk of cancer for a variety of anatomic sites that is associated with higher consumption of tomatoes and tomato-based products adds further support for current dietary recommendations to increase fruit and vegetable consumption.

Giovannucci E.

Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA 02115, USA. edward.giovannucci@channing.harvard.edu

J Natl Cancer Inst. 1999 Feb 17;91(4):317-31.

Serum Lycopene, Other Carotenoids, and Prostate Cancer Risk: a Nested Case-Control Study in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

TLP — Tue, 03 Jul 2007 18:06:58 +0000

Background: Reports from several studies have suggested that carotenoids, and in particular lycopene, could be prostate cancer–preventive agents. This has stimulated extensive laboratory and clinical research, as well as much commercial and public enthusiasm. However, the epidemiologic evidence remains inconclusive.

Materials and Methods: We investigated the association between prediagnostic serum carotenoids (lycopene, {alpha}-carotene, ß-carotene, ß-cryptoxanthin, lutein, and zeaxanthin) and risk of prostate cancer in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a multicenter study designed to examine methods of early detection and risk factors for cancer. The study included 692 incident prostate cancer cases, diagnosed 1 to 8 years after study entry, including 270 aggressive cases, with regional or distant stage (n = 90) or Gleason score ≥7 (n = 235), and 844 randomly selected, matched controls. As study participants were selected from those who were assigned to annual standardized screening for prostate cancer, results are unlikely to be biased by differential screening, a circumstance that is difficult to attain under non–trial conditions.

Results: No association was observed between serum lycopene and total prostate cancer [odds ratios (OR), 1.14; 95% confidence intervals (95% CI), 0.82-1.58 for highest versus lowest quintile; P for trend, 0.28] or aggressive prostate cancer (OR, 0.99; 95% CI, 0.62-1.57 for highest versus lowest quintile; P for trend, 0.433). ß-Carotene was associated with an increased risk of aggressive prostate cancer (OR, 1.67; 95% CI, 1.03-2.72 for highest versus lowest quintile; P for trend, 0.13); in particular, regional or distant stage disease (OR, 3.16; 95% CI, 1.37-7.31 for highest versus lowest quintile; P for trend, 0.02); other carotenoids were not associated with risk.

Conclusion: In this large prospective study, high serum ß-carotene concentrations were associated with increased risk for aggressive, clinically relevant prostate cancer. Lycopene and other carotenoids were unrelated to prostate cancer. Consistent with other recent publications, these results suggest that lycopene or tomato-based regimens will not be effective for prostate cancer prevention.

(Cancer Epidemiol Biomarkers Prev 2007;16(5):962–8)

Full Text

Ulrike Peters1,2,3, Michael F. Leitzmann3, Nilanjan Chatterjee3, Yinghui Wang1, Demetrius Albanes3, Edward P. Gelmann4, Marlin D. Friesen5, Elio Riboli6 and Richard B. Hayes3

1 Fred Hutchinson Cancer Research Center; 2 University of Washington, Seattle, Washington; 3 Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Department of Health and Human Services, Rockville, Maryland; 4 Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, District of Columbia; 5 Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; and 6 Nutrition and Cancer Unit, International Agency for Research on Cancer, Lyon, France

Requests for reprints: Ulrike Peters, Cancer Prevention Program, Fred Hutchinson Cancer Research Center, P.O. Box 19024, 1100 Fairview Avenue North M4-B402, Seattle, WA 98109-1024. Phone: 206-667-2450; Fax: 206-667-7850. E-mail: upeters@fhcrc.org

Lutein

TLP — Wed, 28 Mar 2007 13:10:21 +0000

Lutein (from Latin lutea meaning “yellow”) is one of over 600 known naturally occurring carotenoids. Found in green leafy vegetables such as spinach and kale, lutein is employed by organisms as an antioxidant and for blue light absorption. Lutein is covalently bound to one or more fatty acids present in some fruits and flowers, notably marigolds.

Lutein was found to be present in a concentrated area of the macula, a small area of the retina responsible for central vision. The hypothesis for the natural concentration is that lutein helps protect from oxidative stress and high-energy light. Various research studies have shown that a direct relationship exists between lutein intake and pigmentation in the eye. Several studies also show that an increase in macula pigmentation decreases the risk for eye diseases such as Age-related Macular Degeneration (AMD).

Lutein is a natural part of human diet when fruits and vegetables are consumed. For individuals lacking sufficient lutein intake, lutein-fortified foods are available, or in the case of elderly people with a poorly absorbing digestive system, fortification via a sublingual spray ensures maximum benefit to the eyes. As early as 1996, lutein has been incorporated into dietary supplements. While no recommended daily allowance currently exists for lutein as for other nutrients, positive effects have been seen at levels of 6 mg/day. The only definitive side effect of excess lutein consumption is the same observed for β-carotene overdose, namely bronzing of the skin (carotenodermia). The normal levels of Lutein found in a daily vitamin tablet can be as low as 0.25 mg.

Resveratrol

TLP — Wed, 28 Mar 2007 12:11:27 +0000

Resveratrol is a phytoalexin (antibiotics produced by plants that are under attack) found in the skin of red grapes and as a constituent of red wine. Resveratrol and other grape compounds have been positively linked to fighting cancer, heart disease, degenerative nerve disease, and other ailments. Red wine typically has health benefits not found in white wine (with some exceptions) because many of these compounds are found in the skins of the grapes and only red wine is fermented with the skins.

Flavonoids

TLP — Wed, 28 Mar 2007 12:00:08 +0000

Flavonoids (bioflavonoids in the media) are phenylpronanoids, a class of plant-derived organic compounds that are biosynthesized from the amino acid phenylalanine and belonging to the polyphenol group, characterized by the presence of more than one phenol group per molecule. Flavonoids are most commonly known for their antioxidant activity.

Polyphenols

TLP — Wed, 28 Mar 2007 11:59:58 +0000

Polyphenols are a group of chemical substances found in plants, characterized by the presence of more than one phenol group per molecule. Polyphenols are generally further subdivided into tannins, and phenylpropanoids such as lignins and flavonoids.

Phenylpropanoids

TLP — Wed, 28 Mar 2007 11:59:49 +0000

Phenylpropanoids are a class of plant-derived organic compounds that are biosynthesized from the amino acid phenylalanine. This class includes: cinnamic acids, cinnamic aldehydes and monolignols, coumarins and flavonoids, stilbenoids. They have a wide variety of functions, including defense against herbivores, microbial attack, or other sources of injury; as structural components of cell walls; as protection from ultraviolet light; as pigments; and as signaling molecules.

Vitamin C

TLP — Wed, 28 Mar 2007 11:59:30 +0000

Vitamin C or L-ascorbate is an essential nutrient required to allow a range of essential metabolic reactions in animals and plants, and widely known as the vitamin that prevents scurvy in humans. The pharmacophore of vitamin C is the ascorbate ion. In living organisms, ascorbate is an antioxidant, as it protects the body against oxidative stress, and a cofactor in several vital enzymatic reactions. As a nutrient, its uses and requirements are matters of on-going debate. The North American Dietary Reference Intake recommends 90 milligrams per day and no more than 2 grams per day (2000 milligrams per day). As a food additive, vitamin C is used as an antioxidant preservative and an acidity regulator. Several E numbers account for the vitamin, depending on its chemical structure: E300 as ascorbic acid, E301 as sodium ascorbate, E302 as calcium ascorbate, and E303 as potassium ascorbate.

Retinol

TLP — Wed, 28 Mar 2007 11:56:11 +0000

Retinol, the animal form of vitamin A, is a yellow fat-soluble, antioxidant vitamin important in vision and bone growth. It belongs to the family of chemical compounds known as retinoids. Retinol is ingested in a precursor form; animal sources (milk and eggs) contain retinyl esters, whereas plants (carrots, spinach) contain pro-vitamin A carotenoids. Hydrolysis of retinyl esters results in retinol while pro-vitamin A carotenoids can be cleaved to produce retinal. Retinal, also known as retinaldehyde, can be reversibly reduced to produce retinol or it can be irreversibly oxidized to produce retinoic acid. The best described active retinoid metabolites are 11-cis-retinal and the all-trans and 9-cis-isomers of retinoic acid.