Lycopene is a naturally present, lipid soluble carotenoid (with non-provitamin A activity) in tomatoes which gives fruits and vegetables red color. Lycopene is often regarded as an effective remedy for the prevention of certain malignancies, especially prostate cancer. However, studies vary as to the effectiveness of lycopene. Animals and humans do not synthesize lycopene, and thus depend on dietary sources which is largely supplied by tomatoes and tomato-based products (tomato juice, ketchup, tomato paste, tomato soup, pizza sauce and spaghetti sauce). As a supplement, lycopene is usually incorporated in multivitamin and multimineral products due to its potent antioxidant activity (twice that of beta-carotene and 10 times higher than that of alpha-tocopherol in vitro). A relatively small proportion of lycopene can also be found in watermelon, pink grapefruit, apricots, pink guava and papaya.
Bioavailability and Absorption
The different isomeric forms of lycopene are suggested to greatly influence its bioavailability and absorption as majority of dietary lycopene exists in the linear, all-trans form (95% in tomatoes), human tissues contain mainly cis-isomers (60% in human plasma) . Therefore, the lycopene found in processed tomatoes such as tomato paste is up to 2.5 times more bioavailable than lycopene found in fresh tomatoes . How tomatoes are processed may also influence lycopenes bioavailability. Cooking and heating breaks down cell walls which enhances cis isomerization making lycopene more accessible . Bioavailability and absorption can also be enhanced by coingestion of dietary fats or other carotenoids such as beta-carotene.
Effects on Men’s Health
Lycopene has attracted much attention due to its effects as a natural antioxidant. As men age the risk of benign prostatic hyperplasia (enlarged prostate or BPH) is increasing, which also increases the risk for developing prostate cancer. Strong antioxidative action of lycopene have been suggested to assist in the prevention and treatment of BPH and prostate cancer, however evidence is inconsistent. While some early studies show that lycopene slows the progression of prostate enlargement and improves symptoms [4,5,6,7], other studies failed to find such link [8,9]. Besides antioxidant action, inhibition of prostatic IGF-I signaling, IL-6 expression, and androgen signaling are suggested mechanisms of action of lycopenes efficacy in preventing of benign prostate hyperplasia . A systematic review  which included 8 randomized, placebo-controlled trials (three graded as posing high risk of bias) reported that it is not possible to draw a firm conclusion regarding the use of lycopene for the prevention or treatment of BPH or prostate cancer. The few clinical trials that evaluated the effect of lycopene on prostate cancer growth have reported mainly the short-term effects on the level of prostate-specific antigen (PSA) in the blood, which is generally considered a good indicator of prostate cancer growth .
Some early research in humans has also shown benefits of lycopene together with saw palmetto and selenium in treating prostate inflammation . However, the use of lycopene alone for this condition remains unclear.
Given the lack of any hard scientific evidence and lack of potential risks of excess dietary intake of supplemental lycopene it is premature to recommend it for such conditions.
It has been suggested that oxidative damage may negatively affect sperm  and that the use of oral antioxidants in infertile men could improve sperm quality and pregnancy rates  and since is it believed that lycopene has potent antioxidant effect it has been studied for use in male subfertility. A preliminary report  demonstrates a possible role of oral lycopene therapy in the improvement of semen parameter. The study noted a statistically significant improvement in sperm concentration and motility. Mendiola et al.  also demonstrated a positive association between lycopene intake and semen quality. In Bisphenol A (BPA, 2,2-bis(4-hydroxyphenyl) propane) intoxicated animals, lycopene exhibited marked reduction of testicular damage . Pretreatment with lycopene might also prevent adriamycin-induced spermiotoxicity .
Larger, randomized, placebo-controlled trials are needed to affirm these initial observations.
Many human and animal data suggests that consuming tomato products reduces serum testosterone levels [10,20,21]. Besides being anabolic, testosterone is also critical hormone that impacts prostate development, biology, and promotes prostate carcinogenesis . So, reduced testosterone action is positively associated with prostate cancer risk . However, this reduces serum testosterone levels seem to be only affected acutely  as previously feeding tomato powder or lycopene for weeks or months did not affect serum testosterone levels.
Lycopene and Diabetes Link
In diabetic animal models lycopene has been shown to reduce diabetes-associated learning and memory impairment , and attenuate diabetic neuropathic pain . In Type 2 diabetic patients, lycopene may be beneficial as it reduced oxidative stress and enhances innate immunity or serum levels of immunoglobulin M . One large prospective cohort study  of a total of 35,783 women (aged ≥45), found no associations between lycopene or lycopene-containing foods and the risk of type 2 diabetes mellitus. Same was noted by another similar study .
More high-quality research is needed to better evaluate possible benefits of lycopene for patients with diabetes.
Side Effects and Toxicity
Lycopene is regarded as safe when taken in recommended amounts for up to one year. Some minor adverse effects were noted, namely skin itching, heartburn and flatulence 
(Other common names: All-Trans Lycopene, Cis-Lycopène, Licopeno, Lycopène, Lycopenes, Likopen, Lycopin, Rhodopurpurin, non-provitamin A carotenoid, Psi, Psi-Carotene)
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