“Occasionally,… positive things happen in the field of cancer prevention science to popular, good-tasting foods.” Yes, broccoli family vegetables are wonderful, but may be “a hard food for the public to swallow.” By contrast, who doesn’t like tomatoes?
But, studies using high-dose supplements of lycopene, the antioxidant red pigment in tomatoes thought to be the active anticancer ingredient, failed over and over again to prevent or treat cancer, and may even end up promoting it—since at the high levels one can get with supplements, lycopene may actually act as a pro-oxidant. But, lycopene in supplement form doesn’t appear to be effective at lower doses, either. “There is a strong [protective] correlation between the intake of [actual whole] fruit[s] and vegetables and the incidence of certain cancers.” But when we supplement with only a single compound isolated in pill form, we may upset the healthy natural balance of antioxidants.
It does seem to be quite the human hubris to think we can reproduce “the beneficial effects of consuming entire fruits and vegetables” by giving supplements of a single phytochemical, which would normally interact with thousands of other compounds in “the natural matrix” Mother Nature intended. In addition to lycopene, other carotenoids in tomatoes include beta-carotene, gamma-carotene, zeta-carotene, phytofluene, and phytoene, all of which are known “to accumulate in human prostate tissue.” And, “there are also numerous non–carotenoid compounds in tomatoes that [may] have [anti-cancer] activity”—not to mention all the compounds we have yet to even characterize.
But, it’s not about finding the one magic bullet: “The anti-cancer effects of carotenoids and other phytonutrients may reside in [their] combined activity.” For example, at the low concentrations of the tomato compounds phytoene, phytofluene, and lycopene found in most people who eat normal amounts of tomatoes, there’s very little effect on cancer cell growth in vitro, used separately. But combine them all together, and a non-effective dose plus a non-effective dose becomes effective somehow, significantly suppressing prostate cancer cell growth.
And, the same synergy can be seen across foods. Curcumin, the yellow pigment in turmeric and curry powder, tomato extracts, and the vitamin E found in nuts and seeds do little to inhibit pro-growth signaling of prostate cancer cells—less than 10%. But all three together suppresses growth signaling like 70%. The whole is greater than the sum of its parts.
So, how about instead of giving cancer patients lycopene pills, we give them some tomato sauce? “Thirty-two patients with localized prostate [cancer]” were given three-quarters of a cup of canned tomato sauce every day “for 3 weeks…before their scheduled radical prostatectomy.” In their bloodstream, PSA levels dropped “by 17.5%.” PSA, prostate-specific antigen, is a protein produced by prostate gland cells, and elevated blood levels are routinely used “to monitor the success of [cancer] treatment. It was surprising to find that,” in just three weeks, a “tomato sauce-based dietary intervention” could decrease PSA concentrations in men with prostate cancer. Also, free radical damage of the DNA in their white blood cells dropped by 21%. Imagine how antioxidant-poor their diet must have been beforehand, if less than a cup of tomato sauce a day could reduce DNA damage by more than a fifth.
Okay, but what did they find in their prostates? “[H]uman prostate tissue [is thought to] be particularly vulnerable to oxidative DNA damage by free radicals, which are thought to play a critical role in all stages of [cancer formation].” This may be for a number of reasons, including “fewer DNA repair enzymes.” Well, the researchers had tissue samples taken before the tomato sauce from biopsies, and tissue samples after the three weeks of tomato sauce from the surgery, and resected tissues from tomato sauce-supplemented patients had 28% less free radical damage than expected. Here’s the DNA damage in the prostate before the tomato sauce, and here’s after. Just 20 days of sauce. And, what’s interesting is that “[t]here was no association between” the level of lycopene in the prostate and the protective effects. Tomatoes contain a whole bunch of things, some of which may be even more powerful than lycopene.
Regardless, in contrast to the lycopene supplements alone, “the whole-food intervention” seemed to help. To see if lycopene played any role at all, one would have to test a lycopene-free tomato—in other words, a yellow tomato. So, what if you compared red tomatoes to yellow tomatoes, which have all the non-lycopene tomato compounds, to straight lycopene in a pill? So, they fed people red tomato paste, yellow tomato paste, lycopene pills, or placebo pills, and then dripped their blood on prostate cancer cells growing in a petri dish.
Compared to those not eating anything, the red tomato serum, the blood from those who ate red tomato paste, significantly decreased the prostate cancer cell’s expression of a growth-promoting gene called cyclin D1. This downregulation of the gene by the red tomato consumption “may contribute to lower prostate cancer risk by limiting cell proliferation.” The red tomato seemed to work better than the yellow; so, maybe the lycopene helped, but not in pill form. “[T]his gene was not regulated by [the lycopene-pill serum],” indicating that maybe it’s something else. And, lycopene alone significantly upregulated “procarcinogenic genes. Therefore, it can be stated that tomato consumption may be preferable.”
So, what’s the best way? A spouse wrote in to the editor of the Harvard Men’s Health Watch saying his or her husband “wants to have pizza…for his prostate”—to which the doctor replied, fine, but how about “cheese-free pizza (with broccoli instead of pepperoni)”, or, he can just drink some “tomato juice.”