How Tomatoes Protect Against Cancer — and When They Don’t

This Week’s Research Highlight

Tomatoes weren’t supposed to be the standout.

In 1995, a landmark study tracked the diets of nearly 48,000 men to investigate which fruits and vegetables might reduce the risk of prostate cancer. Out of 46 different foods analyzed, only four showed a significant protective effect — and three of them were tomato-based.

Men with the highest intake of these foods had a 35% lower risk of developing prostate cancer.

The common thread? Lycopene — the red pigment that gives tomatoes their color.

Since then, lycopene has been studied in hundreds of experiments. Lab models have shown it can interfere with tumor growth, reduce inflammation, and protect DNA.

But in real-world dietary studies, the results have been far less consistent. Some show benefits. Others don’t.

So what’s going on?

A massive new meta-analysis helps make sense of the confusion — and it may finally explain why the most lycopene-rich food in our diet doesn’t always deliver the protective punch we’d expect.

What the Researchers Did

To untangle decades of conflicting data, researchers conducted a systematic review and meta-analysis, combining results from 121 prospective cohort studies — spanning over 4.5 million participants and 100,000 cancer cases.

They organized the data into three categories:

• Tomato consumption, based on self-reported dietary questionnaires

• Lycopene intake, estimated from the same reports

• Blood lycopene levels, measured from serum or plasma samples

Their goal: to determine whether any of these exposures — what people ate or what showed up in their bloodstream — consistently predicted lower cancer risk or death.

To keep things consistent, they excluded studies focused on specific tomato products like sauce or paste — a methodological choice that, as we’ll see, may have filtered out the most potent sources of lycopene.

By pairing dietary reports with biomarker data, this study wasn’t just asking whether tomatoes or lycopene protect against cancer. It was probing a deeper question:

Is the real driver of protection what we eat — or what our bodies actually absorb?

The Strongest Signal: Lycopene and Cancer Death

Across the board, people with higher lycopene exposure were less likely to die from cancer — although the strength of that association varied depending on how lycopene was measured:

• Those who ate the most tomatoes had an 11% lower risk of cancer death.

• Those who reported the highest lycopene intake showed a 16% lower risk.

• The strongest signal came from bloodwork: people with the highest blood levels of lycopene had a 24% reduction in cancer mortality. For lung cancer, the effect was even more dramatic — a 35% lower risk of death.

That’s a pretty striking result, especially given that these findings emerged from long-term studies in free-living humans.

Cancer Risk and the Lycopene Divide

When the researchers looked at overall cancer incidence — not just death — a more nuanced picture emerged.

Tomato consumption wasn’t significantly associated with lower cancer risk. Raw tomatoes also showed no effect.

Lycopene, however, did.

People with the highest blood lycopene levels saw an 11% lower risk of developing cancer. And importantly, there was a clear dose–response: for every 10 μg/dL increase in blood lycopene, cancer risk dropped by an additional 5%.

That kind of stepwise relationship strengthens confidence in the finding. When more exposure leads to more benefit, it suggests a true biological effect — not just a statistical blip.

Taken together, these results suggest that lycopene may protect against cancer — but not all tomatoes are equally effective at delivering it.

The difference? Bioavailability: how much lycopene your body can actually absorb and use.

Why Raw Tomatoes Don’t Deliver

Tomatoes are the richest dietary source of lycopene. But eating them doesn’t guarantee lycopene will reach your bloodstream.

In one controlled trial, participants were given the same amount of lycopene from either whole fresh tomatoes or tomato juice. Only the juice raised blood lycopene levels. Despite offering the same dose on paper, the fresh tomatoes had no measurable effect.

Why? Lycopene is tightly bound within the fibrous matrix of raw tomato cells, making it hard to extract during digestion.

In one lab study that simulated the chemical and enzymatic conditions of the human gut, scientists found that only 3.2–4.5% of the lycopene in fresh tomatoes was actually released during digestion  — meaning more than 95% of it likely passes through untouched.

This is where processing comes in. Mechanical disruption — like juicing, blending, or pureeing — physically break open the tomato’s fibrous structure — freeing the lycopene that would otherwise go to waste.

But that’s only half the story.

Heat: A Catalyst for Absorption

Cooking takes bioavailability a step further.

In another feeding trial, researchers compared raw and heat-treated tomato juice. Both contained the same amount of lycopene — but the heated version delivered more than twice as much lycopene to the bloodstream.

Why? Heat doesn’t just soften the plant structure — it transforms lycopene itself.

In fresh tomatoes, lycopene occurs in an all-trans form — a rigid, linear molecule that doesn’t dissolve well in fat and is tough for our intestinal cells to grab onto. Heating twists some of these molecules into cis-isomers — kinked shapes that mix better with fats, survive digestion more reliably, and are more easily absorbed.

In short, cooking makes lycopene more compatible with human physiology.

Cooking converts lycopene’s rigid all-trans structure into bent cis-isomers — the forms your body prefers.

From Arballo et al, 2021.

Now, combine both processes — mechanical disruption and heat — and you get something special: tomato sauce. Or better yet, tomato paste.

Both of these products are made by crushing and simmering tomatoes into a thick, concentrated source of highly bioavailable lycopene. In a head-to-head comparison, tomato paste led to nearly four times more lycopene absorption than fresh tomatoes — despite ostensibly offering the exact same lycopene content.

Why the Numbers Didn’t Add Up

So, this is where the puzzle comes together.

In the meta-analysis, researchers included only studies reporting total tomato intake — not specific products like sauce or paste.

That choice made sense methodologically. But nutritionally, it may have been a miss.

As we’ve seen, processed tomato products are the most effective sources of lycopene. Excluding them means the dietary data didn’t capture the foods that actually deliver it best.

Blood levels, in contrast, reflect absorption — regardless of food source. And that’s where the strongest cancer protection showed up.

This idea isn’t new. That 1995 study we opened with found that tomato sauce and pizza were the most protective foods for prostate cancer. These aren’t just incidental sources of lycopene — they’re actually the forms that deliver it best!

And maybe the key lesson from this whole body of research is this: When it comes to tomatoes, it’s not just what you eat — it’s the form it takes.

Processing, For Better and For Worse

There’s a popular nutrition rule: the less processed, the better.

And most of the time, it kind of holds. Highly processed foods — packed with sugar, starch, artificial flavorings, and industrial oils — are linked to obesity, diabetes, and early death.

But that heuristic has exceptions.

Tomatoes appear to be one of them.

In raw form, they’re rich in lycopene — but poorly absorbed. Juicing or blending breaks open plant cells. Cooking transforms lycopene into absorbable forms. And pairing it with a little fat boosts absorption even more.

In this case, processing doesn’t degrade nutrition. It activates it.

So if you're eating tomatoes for their health benefits, the best versions may not be fresh from the garden — but stewed, simmered, or spooned out from a can.

Summary: In a large meta-analysis of 121 prospective cohort studies involving over 4.5 million participants, researchers examined whether tomato consumption, dietary lycopene intake, or blood lycopene levels were linked to cancer outcomes. While higher tomato intake and reported lycopene consumption were associated with modest reductions in cancer mortality (11% and 16%, respectively), the strongest and most consistent signal came from blood lycopene levels. Individuals with the highest blood lycopene had a 24% lower risk of cancer death and an 11% lower risk of developing cancer overall, with a clear dose–response relationship — every 10 μg/dL increase in blood lycopene was linked to a 5% drop in cancer risk. The findings suggest that lycopene may be protective against cancer, but that absorption, not just intake, is what truly matters.

Random Trivia & Weird News

🍅  The Tomato Effect is a medical term for when a therapy is dismissed not for of a lack of efficacy, but because it violates our expectations.

In 1820, Americans believed tomatoes were poisonous.

To prove them wrong, Colonel Robert Gibbon Johnson allegedly staged a public stunt to prove them wrong. He marched through the streets of Salem, New Jersey, climbed the courthouse steps, and — in front of 2,000 people — ate an entire basket of tomatoes.

A woman screamed and fainted. The crowd watched in horror… until he didn’t die. Then came the cheers and the music. And America subsequently learned to love tomatoes.

Today, medicine has a term for this phenomenon: the Tomato Effect — when a treatment is rejected, not because it doesn’t work, but because it doesn’t seem like it should. A reminder that sometimes, our biggest blind spots are the ones we’re most certain about.

Podcasts We Loved This Week

• Duane Mellor: Rethinking ultra-processed foods in the modern food system. Via Sigma Nutrition Radio.

• Martha Clokie, James Ebdon, Claas Kirchhelle: Bacteriophages. Via In Our Time.

Products We Like

Tuscanini Premium Double Concentrated Tomato Paste

Shelf-stable, ultra-concentrated, and easy to portion without waste — this is basically a lycopene delivery vehicle in a squeeze tube.

I like to keep these in the fridge and use them on an ongoing basis as a stealth nutritional upgrade for soups, sauces, sautéed greens, and other dishes.

humanOS Catalog Feature of the Week

How-to Guide: Smoothies

We often think of food processing as something to avoid.

But sometimes, the right kind of processing — like blending or cooking — can actually unlock nutrients that are otherwise trapped or poorly absorbed.

That’s the philosophy behind our How-To Guide to Smoothies.

Built around evidence-based principles, the guide shows you how to use mechanical processing (i.e., your blender!) to boost nutrient density, increase fiber intake, and deliver hard-to-access phytochemicals in a delicious, convenient form. It’s all about getting more from the plants you already eat.

To Access:

1. Log in to humanOS.
2. See How-to Guides in navigation on the left-hand side
3. Scroll down to Smoothies (in the middle column, close to the bottom)

Also, you can search “smoothies” in the search field after you’ve logged in:

Wishing you the best,