Canned tomatoes: Balancing benefits with hidden health risks

Canned tomatoes are sumptuous as a base for sauces or soups, enhance ratatouille, salsa, or a smoothie, and can be used to prepare pizza, shakshuka, and homemade ketchup—the virtues of canned tomatoes are numerous. But do these products have only advantages?

Italians are primarily known for canned tomato production, but this method of preserving delicious vegetables (botanically fruits) originated in the United States. Harrison Woodhull Crosby, the chief gardener at Lafayette College in Pennsylvania, is considered the pioneer, having developed a primitive method for "canning" tomatoes in 1847.

Just 10 years later, American President Abraham Lincoln, a great lover of tomatoes personally, admired them in one of his letters: "canned tomatoes are a testament to human ingenuity and innovation." However, cans were made manually until the end of the 19th century. Developing a mechanical production method led the product to gain widespread recognition, which persists today.

Store shelves, bending under the weight of canned tomatoes, testify to this. They are whole or diced, often with various additives: basil, garlic, or chili peppers. Their form makes them easy to use and ready to eat straight out of the can. They form an excellent base for many Italian, Greek, Spanish, Balkan, or Mexican dishes. They are perfect for making sauces, meat dishes, and even soups, such as the tomato soup so loved by Poles.

What should you know before buying them?

Undoubtedly, tomatoes in any form are a product with significant nutritional benefits. They are a treasure trove of lycopene – a pigment that gives them their intense red colour. Lycopene is a potent antioxidant that effectively inhibits the harmful activity of free radicals, accelerating the body's ageing processes and contributing to cardiovascular diseases and cancer (an appropriate dose of lycopene reduces the risk of prostate and colorectal cancer).

Just one large tomato can cover nearly half of our daily vitamin C requirement, which strengthens the immune system, protects it from infections, slows down ageing processes, and regulates the cardiovascular system. This juicy treat is also a rich source of vitamins A, E, and B group vitamins and numerous minerals, especially potassium – an element essential for maintaining proper blood pressure and critically important for regulating the body's water balance.

These benefits are also present in canned tomatoes, provided they are the main ingredient of the preserve. Typically, they constitute 60-65% of the can's contents, with the rest being tomato juice. However, preserves with 98-99% tomato content are worth looking for.

Most canned tomatoes available on the UK market also contain salt. However, products without this addition can be found, which is beneficial as people already overconsume salt – the average UK resident consumes twice the daily sodium chloride dose recommended by the World Health Organisation. The effect? A significantly increased risk of developing hypertension, stroke, and other cardiovascular diseases. Excessive salt intake also poses a risk of osteoporosis, kidney disease, and stomach cancer.

Most canned tomatoes contain citric acid (coded as E 330), which functions as an acidity regulator. Although it is considered safe for health, in excess, it can sometimes damage dental enamel (promoting tooth decay), cause problems with absorbing certain valuable microelements (especially calcium), and exacerbate issues like cold sores. It is worth choosing if you can find a can of tomatoes without this additive.

After opening the can, tomatoes should be used immediately; alternatively, the remaining contents can be transferred to a glass container, along with the juice (to preserve the aroma), and placed in the refrigerator for no longer than 24 hours.

Storing preserves in the open can risk the leaching of Bisphenol A (BPA) – a chemical used to coat the can's interior to protect the contents from contact with metal. Recent scientific studies have shown that long-term absorption of BPA can lead to obesity, hormonal disturbances, and even an increased risk of certain cancers.

Meanwhile, a recent study by the German consumer organisation Öko-Test revealed that out of 20 cans of peeled tomatoes tested (8 were from organic farms), 18 products had high BPA levels.

Therefore, when choosing canned tomatoes, it is best to select those labelled "Bisphenol A free" or "BPA free".