A Little-Known Tomato Compound May Help Protect The Liver, Study Finds

Forget Lycopene: This Colorless Tomato Compound Protected Mouse Livers

Lycopene has long taken credit for the tomato’s reputation as a health food. But new research out of Tufts University points to a colorless, overlooked relative of lycopene called phytoene, and the tomatoes richest in it aren’t the bright red ones. They’re the pale, white-creamy or golden-orange varieties that most shoppers walk past.

In a study published in Molecular Nutrition & Food Research, scientists fed mice a carbohydrate-heavy diet meant to model the kind of low-quality carbohydrates, including refined grains and added sugars, that make up nearly half of daily calories in the United States and are linked to fatty liver disease. Some mice ate that diet alone; others got the same diet with a phytoene supplement mixed in. After 24 weeks, the phytoene-fed mice had noticeably less fat buildup in their livers, and the protection held up in both males and females against a condition now affecting roughly one in three people worldwide.

Phytoene had never been well studied on its own, largely living in lycopene’s shadow despite being the very first building block plants use to make lycopene and other pigments. Certain tomato varieties never finish that conversion process, leaving them pale in color but unusually rich in phytoene itself. If phytoene carries real protective power on its own, that reframes which tomatoes deserve a spot in the cart.

Mice Missing Two Key Enzymes Put Phytoene to the Test

Researchers worked with two groups of mice: normal, healthy mice and a special strain engineered to lack a pair of enzymes, called BCO1 and BCO2, that the body normally uses to break carotenoids like phytoene down into smaller, active fragments. Comparing the two groups was the key to the experiment’s central question, whether phytoene protects the liver on its own or whether the body first has to break it down chemically to get any benefit.

Both groups ate the high-carbohydrate diet for 24 weeks, a timeframe long enough to reliably produce fatty liver disease in past experiments from this same lab. Half of each group’s diet was supplemented with phytoene at a dose calibrated to be achievable through ordinary eating; the paper’s authors calculated the human equivalent at roughly 9.6 milligrams a day, an amount available from about half a cup of tomato paste. Researchers tracked body weight weekly throughout the study, and at its end they examined liver tissue under a microscope, measured how much fat had accumulated, and ran genetic tests to see which biological pathways phytoene might be switching on.

Phytoene Only Protected the Liver When the Enzymes Were Present

In the normal mice, phytoene substantially reduced liver fat scores, and fat stored in the liver also fell in both sexes. Treated mice also gained less weight overall. But in mice missing the two enzymes, phytoene barely moved the needle, even though it built up in their liver and blood at two to nearly five times the levels seen in the normal mice. With nowhere to be broken down, it just sat there.

That contrast is the heart of the finding: the results suggest phytoene needs to be processed by BCO1 and BCO2 before it can do the liver any good. That processing was also linked to higher activity in a liver protein called SIRT1 and a set of related pathways that push liver cells to burn stored fat instead of stockpiling more of it. It’s a bit like a package that only does anything once it’s been opened, the wrapping paper alone was never going to help.

That evidence, though, comes with a built-in warning against overreach: phytoene accumulated far more strongly in mice missing the enzymes than in normal mice, yet those animals got no protection at all. That’s compelling evidence that processing matters, but it doesn’t pin down exactly which breakdown product is doing the work, or prove the complete chain of cause and effect.

Female mice built up substantially more phytoene in liver and blood than males, with concentrations running roughly double to more than three times higher, possibly tied to estrogen’s effect on how efficiently the compound gets absorbed. Researchers also expected phytoene to reshape the gut microbiome, since a whole-tomato diet has done so in earlier lab experiments, but pure phytoene alone left the measured gut bacteria largely unchanged, suggesting microbiome changes weren’t necessary for the liver benefit seen in these mice.

Some limitations are worth flagging for anyone tempted to buy tomato paste by the case. This was a mouse study, not a human trial, and mice and humans don’t process carotenoids identically, though phytoene does appear to be well absorbed in both. The research also used purified phytoene rather than whole tomatoes, which contain a mix of other potentially beneficial compounds like fiber and polyphenols, and this study alone doesn’t tell us whether the same protection occurs in humans.

Even with those caveats, the findings hand phytoene a promotion, from a passive lycopene byproduct to an active player in the tomato’s health benefits, so long as the body can break it down. That gives researchers another reason to take a closer look at phytoene-rich pale and golden tomatoes, the ones usually passed over at the store for looking underripe.

---

Disclaimer: This article summarizes findings from an animal study and is intended for general informational purposes. It is not medical advice. Consult a healthcare provider before making dietary changes based on this research.

---