which vegetables are the healthiest?

‘Can I have raw vegetables?’ It took some effort, but it’s finally here. The children (6, 9 and 11 years old) ask for vegetables themselves, instead of father and mother having to open the box of tricks to get something healthy in it.

How we do it now: give the children a screen when you start cooking yourself and then put a bowl of vegetables in front of them. Because of the time, just before dinner, they are very hungry. And staring at Paw Patrol or Tiki Taka Touzani then they shove everything in mindlessly.

Well done, I thought, until my girlfriend glanced at the contents of the bowls I served the children. ‘Almost just cucumber. There’s nothing in it, you might as well give them water.’

Science has long since established that vegetables are important. Who enough vegetables food (250 grams per day for an adult) has a lower risk of cardiovascular disease, type 2 diabetes and various types of cancer. But does it also matter which vegetables you eat? And is the cucumber then ‘the sucker’ among vegetables, while other vegetables have super powers?

The CDC, the American variant of the RIVM, has already published a real ranking of ‘powerhouse fruits and vegetables’, with watercress, Chinese cabbage and chard in the top three. Cucumber is missing from the list. The health effects of vegetables and other foods can count on growing scientific interest, with more publications every year. At the same time, the research area is a methodological minefield, warns Ellen Kampman, nutrition professor at Wageningen University. She needs little of ‘superfoods’ and rankings, because it is too difficult to demonstrate the effect of one food.

Health effects of food sometimes only become visible after decades

On the one hand, there are the observational studies, where scientists track and question large numbers of people for years about their dietary habits. The problem with this is that people who eat a lot of fruit and vegetables can also be ‘different’ in other ways, for example because they exercise more or drink less alcohol. Kampman: ‘You can try to correct for that, but it is always tricky.’

Other methods are animal studies or experimental studies in which one group eats a lot of product X for a while, while a control group does not and then, for example, blood values ​​are compared. Kampman: ‘There are also problems with such studies. Humans are different from animals. And the health effects of food sometimes only become visible after decades, so a short-term experimental study is not the cure-all.’

It is the sum of all those different types of studies after which scientists dare to draw firm conclusions. Kampman: ‘Take fiber, which is also found in a lot of vegetables. All the research points in the same direction: those who eat a lot of it lower the risk of colon cancer. The biological mechanism is also clear: intestinal bacteria are happy with fiber and then secrete fatty acids that are beneficial for intestinal cells.’

‘Eating your tomatoes is good for your prostate’

According to Kampman, the category ‘needs further research’ includes studies into tomatoes and prostate cancer. According to a recent American study among Seventh-day Adventists who eat cooked or canned tomatoes five to six times a week, they have a 28 percent lower risk of prostate cancer than Seventh-day Adventists who never eat them. The study is extra strong because Seventh-day Adventists are often vegetarians anyway and pay attention to a healthy diet, which makes the subjects more comparable.

Kampman: ‘When my children were still young, I already saw studies that pointed to this effect. Then I would jokingly say to my son: ‘Eat your tomatoes, it’s good for your prostate’. After which he looked at me wide-eyed and asked what a prostate was.’ But now, twenty years later, Kampman is still not one hundred percent convinced. ‘If the effect is already there, it is small. Genetics and age also play a major role here. This one topic – tomatoes and prostate cancer – does show how long nutritional research can take before there is conclusive evidence.’

Also noteworthy about that American tomato study: the prostate-protective effect did not occur with raw tomatoes. According to the researchers, the explanation for this lies in the substances in the tomato that may protect against cancer: lycopenes, which belong to the antioxidant family. These trap so-called free radicals in the body, aggressive molecules that can damage cells. Fry the tomato in oil and those lycopenes are most easily absorbed by your body, according to the research leader of the Adventist Health Study.

The method of preparation, the transport: everything plays a role

In addition to the type of vegetable, the method of preparation can also determine the effect on health. So examined food technologist Matthijs Dekker, also from Wageningen University, measured the dose of glucosinolates in their meals in people’s homes. These are substances that can also protect against cancer in a normal diet. They can be found in Brussels sprouts, cauliflower and broccoli, for example. Dekker: ‘To my surprise, I discovered that the concentration of glucosinolates could differ enormously between meals of different households. Sometimes by a factor of ten to a hundred, while broccoli is on the menu for all of them.’

The variety, the mode of transport, how long it takes from harvesting to eating: everything plays a role. And the preparation method So also myself, although that is not simple, clear advice. For example, scientists think that the healthy substance lycopene is released better in tomatoes when cooking, but Dekker advises against cooking in water with broccoli. ‘Then you rinse a considerable part of the good water-soluble substances down the sink when you drain. Prefer wok or in the oven. Not too long, the broccoli should still look green.’

Also beware of the pitfall ‘fresh is always better than frozen’, says Dekker. ‘With frozen spinach, the spinach is frozen immediately after harvesting, so that the good substances are preserved. Before fresh spinach ends up on your plate, several days have passed since the harvest, during which some of these substances can be lost.’

Above all, the Wageningen food scientists recommend a varied diet, including different types of vegetables. Edith Feskens, nutrition professor, uses the motto ‘eat all the colors of the rainbow’ as a mnemonic. From red for bell peppers and tomatoes, to orange for carrots, and that’s how you get to green for lettuce and cucumbers. ‘Cucumbers with peel contain a lot of fiber and a bonus: they are filling, so that there is less appetite for sweets and chips.’