Do Tomato Seeds Cause Cancer? - A Complete Evidence-Based Analysis

Do Tomato Seeds Cause Cancer?

Tomatoes are one of the most popular and widely consumed vegetables worldwide. However, there are conflicting claims regarding the health effects and safety of tomato seeds, which are usually discarded when tomatoes are prepared or cooked. Some sources raise concerns that substances like solanine or lectins in tomato seeds may be toxic or carcinogenic.
This thorough article will analyze the scientific evidence behind tomato seed safety and any potential cancer risks. Read on to learn about the nutritional profile of tomato seeds, their health effects, and whether the consumption of tomato seeds is associated with increased cancer risk.

An Overview of Tomato Seeds

The tomato (Solanum lycopersicum) is a flowering plant in the nightshade family. Inside each tomato fruit are numerous seeds encased in a gelatinous sack. Most people discard the seeds when preparing tomatoes, but the seeds are edible.
Tomato seeds are highly concentrated sources of nutrients and beneficial plant compounds compared to the flesh. Just one ounce (28 grams) of dried tomato seeds contains about:
  • 25-30mg of vitamin E - over 100% of the RDI
  • 2-3g of protein
  • 2g of fiber
  • Iron, phosphorus, magnesium, zinc and copper
  • Potent antioxidants like lycopene and phytosterols
Additionally, tomato seeds consist of 25-30% oil containing essential fatty acids like linoleic, oleic and alpha-linolenic acids. However, there are also some potentially harmful substances found in tomato seeds.

Beneficial Compounds in Tomato Seeds

The nutrients and antioxidants in tomato seeds provide significant health benefits. Here is a summary of the major beneficial substances:

Vitamin E - A potent antioxidant that protects cells from damage and inflammation. It supports healthy skin, immune function, and circulation.
  1. Lycopene - A carotenoid antioxidant that gives tomatoes their red color. It has strong anti-cancer and health-promoting activities.
  2. Phytosterols - Plant compounds that lower LDL cholesterol and reduce heart disease risk. They also have anti-cancer benefits.
  3. Polyphenols - Antioxidants that fight oxidative stress linked to chronic diseases like diabetes and neurodegeneration.
  4. Fiber - Promotes digestive health, regularity, and feeds the good bacteria in the gut microbiome.
  5. Essential Fatty Acids - Omega-3 and omega-6 fats support skin, eye, nerve and brain health. They reduce inflammation.
  6. Magnesium & Potassium - Important minerals that are involved in muscle, nerve and cardiovascular function.
The combination of all these compounds makes tomato seeds nutritional powerhouses when eaten. But some people are concerned about potentially harmful substances found in the seeds as well.

Potentially Harmful Compounds

While tomato seeds have a stellar nutritional profile, they also contain some antinutrients and toxins at low levels, including:
  1. Solanine - A glycoalkaloid toxin found in tomatoes and nightshade plants. In excess, it can be neurotoxic and irritating.
  2. Lectins - Proteins that bind carbohydrates and can damage the gut lining at high doses. Found in many plant foods.
  3. Oxalates - Compounds that interfere with mineral absorption and may cause kidney stones when overconsumed.
  4. Saponins - Bitter compounds with hemolytic activity but also strong anti-cancer effects.
However, these compounds exist in very low concentrations in tomato seeds, and pose minimal risk from typical dietary exposure. But some people think they may cause harm if consumed regularly.

Do Tomato Seeds Cause Cancer? Evaluating the Evidence

Should You Eat Tomato Seeds?

There are two primary concerns that are often raised regarding the potential cancer risk from eating tomato seeds regularly:
  • Solanine toxicity
  • Lectin content
However, extensive research shows neither solanine nor lectins in tomato seeds have any carcinogenic or tumor-promoting activity. Let’s analyze the science behind both of these concerns:

Solanine Toxicity and Cancer Risk

  • The major toxic compound in tomato seeds is solanine, a glycoalkaloid. In high doses, solanine can inhibit cholinesterase enzymes and be neurotoxic.
  • Many glycoalkaloids have been found to be cytotoxic against cancer cells in test tube studies. However, human studies show that normal consumption of solanine does not increase cancer risk.
  • A 2020 review of the anticancer effects of glycoalkaloids found that solanine does not enhance tumorigenesis at normal dietary intakes. Doses up to 4-5mg/kg body weight per day were not considered toxic or carcinogenic in humans.
  • Tomato seeds only contain about 5-10mg per 100g of solanine. A 60kg (132lb) adult would need to eat around 1.5kg of dried tomato seeds to reach the 4mg/kg solanine threshold for toxicity.
  • Therefore, the small amounts of solanine in tomato seeds are far too low to cause cancer or toxicity when seeds are eaten in normal food amounts.

Lectin Harm and Cancer

  • Lectins like tomatine in tomatoes can damage the gut lining at extremely high intakes. This led to speculation that lectins may promote cancer development.
  • However, human studies have not found correlations between normal lectin intake and any cancers. Research shows dietary lectins are safely degraded, poorly absorbed from the gut, and do not exhibit carcinogenic effects.
  • A review of the health effects of dietary lectins concluded they do not cause or aggravate cancer at normal intakes. Extremely high lectin doses are required to initiate DNA damage responses or apoptosis in human cells.
  • Tomato seeds only have about 0.1-1% tomatine by weight. Typical consumption of tomato seeds is not high enough for its lectin content to demonstrate toxicity, let alone increase cancer risk.

Do Tomato Seeds Protect Against Cancer?

Not only is there no evidence that normal ingestion of tomato seeds causes cancer, but emerging research suggests tomato seeds may actually help protect against several types of cancer:

Prostate Cancer
  • Tomato seeds are one of the richest dietary sources of lycopene - containing over 100 times more lycopene than tomato flesh per gram. Multiple studies demonstrate that higher lycopene intake is associated with significantly reduced prostate cancer risk.
  • According to an analysis in the Journal of the National Cancer Institute, men with the highest blood lycopene levels had a 21% lower risk of developing prostate cancer compared to those with the lowest levels. Lycopene from tomato seeds may confer chemo-preventive effects.
Breast Cancer
  • Tomato seed oil high in lycopene and phytosterols has been found in preliminary studies to selectively inhibit the growth of ER+ breast cancer cells. The researchers attributed this anti-proliferative activity mainly to lycopene.
Colon Cancer
  • The fiber in tomato seeds supports the growth of healthy gut bacteria and production of short chain fatty acids like butyrate, which have anti-cancer benefits in the colon. The vitamin E in tomato seeds also protects against colorectal cancer development.
  • According to a 2021 review, tomato seeds inhibited colon cancer cell growth in vitro and in animal studies, indicating they “could be considered as a food with anti-cancer potential.”
Liver Cancer
  • Studies report tomato seed oil exhibits strong antitumor actions against hepatocellular carcinoma (HCC) cells. This indicates it may help combat liver cancer. The antitumor activities are likely due to the antioxidant, anti-inflammatory and immunomodulating effects of compounds in tomato seeds like lycopene.
  • Overall, increasing intake of tomato seeds through the diet or supplements may possibly help lower cancer risk thanks to their stellar nutritional profile. The antioxidant, anti-inflammatory and antimicrobial properties of tomato seed compounds are involved in their chemo-preventive activities.

Other Potential Health Benefits of Tomato Seeds

In addition to possible anti-cancer effects, research indicates tomato seeds and tomato seed oil may also:
  1. Lower cholesterol and protect heart health
  2. Reduce inflammation involved in diseases
  3. Improve blood pressure and circulation
  4. Inhibit kidney stone formation
  5. Combat anxiety and depression
  6. Support brain and cognitive health
  7. Accelerate wound healing
  8. Have antimicrobial effects against pathogens
Tomato seeds truly are nutritional superstars. The scientific data suggests including them in the diet may offer diverse disease-preventing benefits with minimal risks.

Are There Any Side Effects of Eating Tomato Seeds?

For most people, eating tomato seeds is considered very safe with minimal side effects. However, some things to be aware of:
  • People with tomato allergies may react to tomato seed ingestion.
  • Those with kidney issues should moderate intake due to oxalates.
  • Consuming extremely high amounts may cause gastrointestinal upset. Moderation is key.
  • Topical application of tomato seeds/oil can very rarely cause skin irritation.
Always start with small amounts of tomato seeds if trying them for the first time to assess tolerance. Speak to your doctor if taking medications or if pregnant/breastfeeding before adding tomato seeds to your diet.
Overall, research shows tomato seeds are very well tolerated with no serious side effects expected at normal dietary intakes.

Conclusion - Should You Eat Tomato Seeds?

Tomato seeds are highly nutritious yet overlooked parts of the tomato. They are rich sources of antioxidants like lycopene and vitamin E, fiber, minerals, healthy fats and bioactive plant compounds.
Numerous studies demonstrate the beneficial effects tomato seeds and their components can have on health - ranging from reducing inflammation to supporting heart health, brain function, and wound healing.
Crucially, research does not support fears about solanine or lectins in tomato seeds promoting cancer. The tiny amounts present in tomato seeds are far below toxic thresholds and do not increase cancer risk through dietary exposure. On the contrary, the anticancer potential of nutrients like lycopene may lower cancer likelihood.
While more research is still needed, the current evidence indicates tomato seeds are very safe to eat and provide important nutrients. Incorporating tomato seeds into recipes, smoothies or other dishes can be an easy way to enhance your nutritional intake and possibly protect against chronic diseases.
Instead of discarding tomato seeds, consider utilizing this nutritious component of the tomato to boost your overall health and wellbeing. Just be sure to consume in moderation. For most people, enjoying tomato seeds as part of a varied, plant-based diet poses no risks and provides significant benefits.