How healthy are tomatoes?

Tomatoes have come a long way since the 16th century, when some Europeans called them “poison apples” because they were mistakenly believed to be toxic. Now, they’re the second-most consumed vegetable in the United States (behind only potatoes) and are recognized for a range of health benefits.

Here’s what nutrition experts say about tomatoes.

They’re hydrating.

Tomatoes are 95% water. One cup of chopped raw tomatoes has nearly 6 ounces of water, making them even more hydrating than watermelon.

Fresh, raw tomatoes have the highest water content, said John Erdman, a professor emeritus of nutrition and food science at the University of Illinois Urbana-Champaign. When they’re cooked, they tend to lose a bit.

Their lycopene may help protect against cancer.

Tomatoes pack a hefty dose of the antioxidant lycopene, whether they’re raw, cooked or sun-dried. Tomatoes and tomato products (ketchup, spaghetti sauce, tomato juice) provide more than 80% of the lycopene in the U.S. diet, Erdman said.

Antioxidants like lycopene can help counteract oxidative stress in our bodies, he said. Over time, that stress can cause chronic inflammation, which in turn can increase the risk for many types of cancers.

Scientists haven’t definitively found that eating foods high in lycopene — or any antioxidant, for that matter — can directly stave off cancer, said Rachel Kopec, an associate professor of human nutrition at the Ohio State University. But human and animal studies — some using tomatoes, some using other sources of lycopene, like supplements — have suggested links between high lycopene levels and lower risk of prostate and lung cancers, among others.

Some studies have also suggested that lycopene could help prevent heart disease, liver disease and other chronic health conditions. But researchers haven’t proven cause and effect here, either, Kopec said.

The redder the tomato, the higher the lycopene level, Erdman said. Orange and yellow tomatoes have a different type of lycopene that presumably has similar health benefits, but researchers haven’t studied it enough to know for sure. Green tomatoes do not contain lycopene.

Cooked tomatoes contain more lycopene than raw ones, added Alice H. Lichtenstein, a professor of nutrition science and policy at Tufts University. That’s because cooked tomatoes become more concentrated when they lose some water. One cup of cooked tomatoes has about 7,300 micrograms of lycopene, as opposed to about 4,600 in raw tomatoes. What’s more, Lichtenstein said, the heat involved in cooking tomatoes breaks down their cell walls, making the lycopene more accessible.

And because lycopene is fat-soluble, eating tomatoes along with a bit of healthy fat can help your body absorb the lycopene, Kopec said. She recommended drizzling tomatoes with olive oil, or pairing them with avocado.

They’re abundant in vitamins and minerals.

Tomatoes are a good source of potassium, said Pinkin Panchal, a dietitian and assistant teaching professor of nutritional sciences at Rutgers University. One large, raw tomato has 431 milligrams of potassium, about as much as a medium-sized banana.

Panchal also noted that tomatoes have decent amounts of folate, a vitamin that helps your cells divide (especially important during pregnancy), and vitamin K, which helps with blood clotting and bone health.

How to enjoy them.

Fresh tomatoes are most nutritious when they’re picked off the vine at peak ripeness, so buying them locally and in season is best, Panchal said.

All of the experts said that while it isn’t necessary to buy organic, rinsing raw tomatoes before eating them can help to remove any lingering pesticides or residue. Panchal said she likes to rinse hers with a capful of distilled white vinegar mixed with water. Vinegar can remove more residue than water alone, she said.

This article originally appeared in The New York Times.