Eat the peels and seeds? What scientifically speaks for and against

Peels, skins, seeds and stems from fruits and vegetables are usually removed during preparation. Many of them contain valuable fiber, as British scientists show.

In a study, they analyzed, on the one hand, how much fiber there is in the parts of plants that are often thrown away. On the other hand, by surveying 40 consumers, they tried to find out why parts of fruit and vegetables are thrown away and how this could be changed.

The study by Rachel Gibson's group from King's College London was published in the “International Journal of Food Sciences and Nutrition”. The team emphasizes that the effects of possible pollutants in the mentioned parts of the plant still need to be researched more thoroughly. But the potential benefits are great.

"The plant parts examined in our study - from root to tip - accounted for between 25 and 48 percent of the total weight of food, meaning a significant portion of the produce purchased is wasted," says Gibson. This is not only a loss of fiber, but also a financial loss, emphasizes the researcher.

Together with her team, Gibson examined parts of plants that are usually cut away for their nutritional value. The foods included beetroot, peppers, broccoli, butternut squash, cauliflower, celery, kale, fennel, kiwi, leeks, pineapple and watermelon.

For most fruits and vegetables studied, the parts removed contained a higher proportion of fiber than the parts normally eaten. The watermelon peel has five times as much fiber per 100 g as the pulp.

Likewise, the proportion of fiber in the peel, seeds and inner parts of butternut squash is around five times as high as in the pulp. Exceptions are broccoli and fennel, where the parts of the plant that are usually thrown away have less fiber than the parts that are eaten.

When surveying consumers, most said that their purchasing decisions are “often” or “always” influenced by taste (85 percent), price (75 percent) and health aspects (70 percent). Accordingly, they were more motivated to eat more than the usual plant parts by the health benefit than by any environmental benefit.

Because if more plant parts were eaten, fewer plants would have to be produced and there would be less waste. However, more than 50 percent of those surveyed do not or rarely take such aspects into account when making purchasing decisions.

It's good when individual consumers use broccoli stems and pepper seeds in dishes at home, says Gibson. However, in order for real change to occur - i.e. reducing food waste while simultaneously increasing fiber intake on a large scale - more needs to be done.

“It would be desirable if catering establishments and food manufacturers examined what fruit and vegetable waste is generated and looked for ways to use it to improve the nutritional value of meals,” explains the researcher. King's College London is setting a good example and has introduced a root-to-tip menu in the cafeteria.

The scientists' motivation is the fact that on average Brits only consume 16.4 grams of fiber instead of the 30 grams recommended by the National Health Service. The fiber content could be increased with root-to-tip meals.

However, the study authors also emphasize that there is still a need for further research: “This also includes dealing with potentially harmful plant ingredients, which could lead to health problems if consumed above safe limits.”

Peels could contain more pesticides or heavy metals than fruit pulp. Certain parts of plants may also naturally contain toxic substances.