What is the role of carotenoids in prostate cancer risk-reduction?

Updated: Oct 11, 2019
  • Author: Mark A Moyad, MD, MPH; Chief Editor: Edward David Kim, MD, FACS  more...
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Answer

Answer

Carotenoids are micronutrient antioxidants that are found in orange or yellow fruits and vegetables and in some dark, leafy vegetables, such as spinach and Brussels sprouts. The most common dietary carotenoids include the following:

  • Beta carotene
  • Alpha carotene
  • Beta cryptoxanthin
  • Lutein
  • Zeaxanthin
  • Lycopene

Lycopene is one of the predominant carotenoids in plasma and in various tissues, including the prostate. It is found in watermelon, tomato and all tomato-based products, pink grapefruit, apricots, papaya, guava, and persimmons. Carrots contain high levels of carotene but contain little lycopene.

Clinical trials that evaluated the role of beta carotene and the risk of developing prostate cancer have indicated, in general, that the risk of prostate cancer is reduced in men with low serum levels of beta carotene who are treated with supplements. However, those findings were generally not from the trials' primary endpoints.

Overall, individual beta-carotene supplements have proved disappointing in their ability to reduce cancer risk. In fact, two large phase III clinical trials (the Alpha-Tocopherol, Beta-Carotene Cancer Prevention [ATBC] [49] and the Beta-Carotene and Retinol Efficacy Trial [CARET] [50] ) raised the possibility that beta-carotene supplements may increase the risk of lung cancer in current smokers, and the Age-Related Eye Disease Study 2 (AREDS2) suggested a potential increase in the risk of lung cancer in former smokers. [51]

Note that beta-carotenes from dietary sources have not been associated with an increased risk of lung cancer. Patients concerned about beta-carotene study results can be reassured that the adverse findings apply only to individual dietary supplements. 

A high intake of tomato products (10 or more servings weekly) has been associated with a 35% decreased risk of advanced prostate cancer; this was independent of fruit, vegetable, and olive oil intake. Additional studies have reported that the incident risk of prostate cancer was reduced by 25-80%. Other studies did not find this association, but some of those were conducted in populations in whom lycopene intake may have been too low to make an association. [52]

Studies comparing high and low intake of tomatoes reported a 10-20%, statistically significant reduction in prostate cancer risk in men with high intake. Cooked tomato products had a stronger effect than raw tomato products. [52]

In contrast with those older dietary data, however, current data (from pooled analysis of prospective studies and updated robust epidemiologic studies) suggest that consumption of tomato products, as well as most other fruits and vegetables, has minimal to no effect on prostate cancer risk. [53, 54]   Regardless, the potential for fruits and vegetables to reduce cardiovascular risk and potentially assist with weight loss should be emphasized while more research in the area of cancer prevention is being conducted. Other carotenoids such as lutein, beta-cryptoxanthin, and zeaxanthin need more research.


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