Tomatoes and Lycopene: Can Eating More Reduce Your Risk of Cancer?

Tomatoes and Lycopene: Can Eating More Reduce Your Risk of Cancer?

New research suggests that lycopene, found in tomatoes and other red fruits, may help reduce the risk of cancer - particularly lung cancer. But is it the key to prevention or just part of a larger health puzzle?

Published in a review and meta-analysis recently published in the journalLimits in nutritionResearchers conducted a systematic review and meta-analysis to examine the association between tomatoes (or lycopene, the organic pigment responsible for red color) and cancer risk or mortality. It included 119 studies for meta-analysis and 121 studies for systematic review from four online scientific repositories.

The study analyzed data from nearly 2.7 million participants, making it one of the largest investigations into lycopene and cancer risk.

The study results suggest that higher consumption of lycopene, rather than tomatoes alone, was associated with modest protective effects against cancer, with higher consumption and blood levels of lycopene being associated with a relative reduction in overall cancer risk of 5-11%. While high tomato consumption was not significantly associated with cancer risk, it was associated with an 11% lower cancer mortality risk. Higher blood lycopene levels were further associated with reductions in cancer-related mortality of 11% and 24%, with the strongest associations observed at higher blood lycopene concentrations. Among specific cancers, lung cancer showed the strongest response to lycopene, with higher blood lycopene levels associated with a 35% lower risk of lung cancer mortality. These findings support the benefits of dietary lycopene intake and blood lycopene levels, and not just tomato consumption. However, the study authors caution that the observed benefits are based on observational data that cannot establish cause.

background

Cancer prevalence and mortality are at an all-time high, with an estimated 20 million new cases and nearly 10 million deaths in 2022. Alarmingly, this number is expected to rise to nearly 30 million new cases per year by 2040, highlighting the need to identify easily accessible preventive measures against these life-threatening conditions.

Processed tomato products such as cooked or pureed tomatoes may provide a more easily absorbed form of lycopene compared to raw tomatoes.

Recent research suggests an intrinsic connection between diet and cancer etiology. It is estimated that food contributes between 5% and 10% of cancer incidence. Fruits and vegetables are of particular clinical interest given the potential protective effects of their high fiber, vitamin C, and antioxidant-rich components.

Tomatoes are increasingly being studied for their anti-cancer potential, with evidence linking higher tomato consumption to reduced cancer risk and delayed progression. Unfortunately, previous research has shown conflicting results, and it remains uncertain whether the observed protective effects are due to lycopene alone or other components in tomatoes. Lycopene, a 40-carbon red pigment from red fruits and vegetables (watermelons, apricots, etc.), is a likely suspect, but its role in cancer risk and mortality requires validation. Notably, more than 80% of global human lycopene intake is acquired through tomato consumption. Emerging evidence suggests that processed tomato products, such as cooked or pureed tomatoes, may provide greater bioavailability of lycopene than raw tomatoes.

About the study

Lycopene intake was associated with lower lung and breast cancer risks, but the evidence for prostate cancer was less clear, highlighting the need for more targeted studies.

The present review includes two components-a systematic review of the available literature on the associations between tomatoes/lycopene consumption and cancer risk/mortality and a dose-dependent meta-analysis to evaluate the amounts of lycopene necessary to produce the anti-cancer benefits suggested by previous research efforts. The study complies with the preferred reporting positions for systematic reviews and meta-analysis (PRISMA) guidelines.

The study data were obtained from four online scientific repositories, namely PubMed, Web of Science, Google Scholar and Scopus, from database initiation to July 2023. Studies were screened for review/meta-analysis based on the following criteria-1. Study design was prospective. y) and 4. Study results were reported as risk ratios (RRS), odds ratios (ORS), or hazard ratios (HRS).

Studies that included combined dietary associations (e.g. tomatoes alongside other foods) were excluded from analyzes to prevent confounding results.

Fixed-effects and random-effects statistical modeling was used to establish and compare cancer benefits in dose-dependent assessments. Heterogeneity between studies was measured using I² statistics and Cochran's Q test. Subgroup analyzes were performed to examine variations in outcomes by geographic region (US NOT), adjustment for body mass index (BMI), and other potential confounding factors. Sensitivity analyzes were performed to check the reliability of the results.

Study results

While this meta-analysis focused on general trends, the researchers note that more studies are needed in less common cancers such as endometrial and skin cancer.

Initial repository queries identified 2,850 potential publications for inclusion in the study. Of these, 302 were duplicates and 2,124 failed title and abstract screening, leading to their exclusion. Of the remaining 154 publications, 121 were included for systematic review and 119 were included in the meta-analyses.

Nineteen publications (30,009 confirmed cancer cases) were assessed for overall cancer risk. The results showed that tomato consumption did not significantly change the overall cancer risk, regardless of the consumption dose. However, when assessing cancer mortality, four publications (249,308 cancer cases and 8,863 deaths) showed that higher tomato consumption was associated with a lower risk of cancer mortality by 11%.

In contrast, lycopene consumption revealed significant inverse correlations between both dietary intake and blood levels of lycopene and cancer risk/mortality. Dose-dependent assessments (2,687,842 participants, 49,617 confirmed cancer cases) showed a relative risk reduction of 5-11% in overall cancer risk with increased lycopene consumption. Cancer mortality assessments found up to a 24% reduced risk between the highest and lowest blood lycopene levels, with dose-response analyzes suggesting that 5-7 mg/day was in the beneficial range. However, 10 mg/day dietary lycopene intake did not provide any additional benefits.

Blood level assessments continued this positive trend, with cancer-associated mortality reduced by 11-24% with higher blood lycopene levels. The strongest association was observed for lung cancer mortality among specific cancer types, where higher blood lycopene levels were associated with a lower risk of 35%. Breast and prostate cancer also showed some protective associations with blood lycopene levels, although dietary lycopene intake alone did not have a significant impact on prostate cancer risk.

Conclusions

The present review highlights the potential protective benefits of lycopene consumption on cancer-related outcomes, particularly when assessing blood lycopene levels. Higher lycopene intake and blood levels significantly reduced cancer risk (by 5-11%) and mortality (up to 24%), with 5-7 mg/day identified as a beneficial range. However, the study also found that 10 mg/day of dietary lycopene intake did not further reduce cancer risk.

These results may usher in a new era of lycopene-centered research aimed at containing the global cancer pandemic and suggest that tomatoes, particularly processed forms with enhanced lycopene bioavailability, may serve as important nutritional components in cancer prevention. However, the researchers emphasize that these results are based on observational data and should not be interpreted as direct evidence that lycopene prevents cancer. Further randomized controlled trials are needed to confirm these associations.

Sources: