Should You Eat Them? The Truth About Fruit Peels and Seeds: What Science Says About Health and Risks

Peel the kiwi, cut off the broccoli stems, and remove the seeds and pulp from the pumpkin. These are tasks we often do without much thought during our usual cooking routine.

But what if those "usually discarded parts" contained dietary fiber?

A study from the UK, introduced by Germany's WELT on November 10, 2026, reevaluates the nutritional value of vegetable and fruit scraps from the kitchen. It's a story that resonates with Japanese dining tables as a way to make better use of purchased ingredients without increasing food costs.

However, the idea that "peels and seeds are nutritious" is different from "any peel or seed can be eaten." It's necessary to separate the possibilities shown by the research from the safety boundaries.

In 10 out of 12 types, the discarded parts had more dietary fiber

The research was conducted by a team led by Rachel Gibson from King's College London. The results were published in the academic journal "International Journal of Food Sciences and Nutrition."

The study focused on 12 types of produce: beets, bell peppers, broccoli, butternut squash, cauliflower, celery, kale, fennel, kiwi, leeks, pineapple, and watermelon.

The research compared the dietary fiber content of the parts usually eaten with the peels and stems often removed during cooking. According to the university's announcement, in 10 out of the 12 types, the parts that tend to be discarded had a higher concentration of dietary fiber.

The WELT article mentions that watermelon rind contains about five times more dietary fiber per 100 grams than the flesh, and the peel and seeds of butternut squash also contain about five times more than the flesh.

On the other hand, broccoli and fennel were exceptions. These had more dietary fiber in the parts usually eaten than in the parts typically removed.

In other words, there wasn't a simple rule that "the outer or harder parts are always more nutritious." The important point is that it varies depending on the ingredient and part.

Don't decide how much to eat based solely on "five times"

In nutritional news, expressions like "five times" catch the eye. However, the figures compared by the same weight and the actual amount that can be consumed in one meal differ.

For example, the dietary fiber content of watermelon rind published by the university was 2.10 grams per 100 grams. Using this measurement, the amount contained in 30 grams would be about 0.63 grams.

There is meaning in gradually utilizing ingredients. However, hearing "five times more than the flesh" and perceiving it as a special food that provides a large amount of dietary fiber at once is premature.

Moreover, the parts used in the analysis and the parts actually cooked at home may not be exactly the same. The hard green outer part of the watermelon and the white part inside cannot be treated the same way.

Researchers explain that they are not recommending eating 100 grams of pumpkin peel or seeds to increase dietary fiber. It's a suggestion to slightly expand the usable parts in everyday cooking.

Even if components are abundant, it doesn't prove health benefits

There is another distinction to keep in mind when reading this research.

It's the difference between knowing "that part contains dietary fiber" and confirming "the health condition of people who continuously ate that part improved."

The focus of the research introduced this time is on the analysis of food components and consumer awareness. It is not a study that followed groups who eat peels and stems and those who don't over a long period, comparing disease incidence rates.

Therefore, it cannot be directly concluded that "eating kiwis with the skin can prevent illness" or "leaving vegetable peels will help you lose weight."

The significance of a diet containing dietary fiber and the health effects of specific peels or seeds need to be understood separately. The research indicates the possibility that parts previously discarded could become a source of dietary fiber.

The motivation to continue is more "tasty and seemingly healthy" than "good for the environment"

The research team also investigated the awareness of 40 consumers regarding this way of eating.

According to the WELT article, the factors that respondents said they "often" or "always" prioritize when purchasing were taste at 85%, price at 75%, and health at 70%. Nutritional benefits were more likely to motivate eating usually discarded parts than environmental benefits.

However, the results of the survey of 40 people cannot be treated as the opinion of the entire UK or Japanese consumers.

Nevertheless, it can serve as a clue when considering implementation at home.

Some people may find it easier to try if they know, "This stem is delicious when stir-fried" or "You can make one more dish with the vegetables you bought," rather than being told to eat for the environment's sake.

Efforts to reduce food waste are difficult to continue if they don't satisfy as a dish. It's necessary to consider ease of cooking, taste, and texture.

On social media, some like stems, while others are puzzled by the texture of peels

On social media and online forums, the topic of "how much of fruits and vegetables to eat" has been discussed for some time.

The following is not a direct reaction to the current paper but a summary of posts on Reddit about the same theme, translated into Japanese. It does not represent overall public opinion.

Regarding kiwis, some people enjoy eating them with the skin, and others are surprised when they talk about eating them with the skin. In another thread, there were reactions concerned about the surface fuzz.

For broccoli stems, more specific cooking tips were shared. Suggestions included removing the hard outer part, slicing thinly, and stir-frying, with some preferring the stems over the florets.

These exchanges suggest that decisions on whether to eat or discard are influenced not only by nutritional knowledge but also by familiarity and texture preferences.

Knowing something is edible increases options. However, not everyone needs to like it. If you dislike kiwi skin, you can choose to use broccoli stems in your cooking.

In a Japanese kitchen, start with broccoli stems

If incorporating this into Japanese dining tables, a manageable entry point would be broccoli stems.

Removing the hard outer part as needed and slicing the inner part thinly makes it easy to add to stir-fries or soups. You can also consider seasoning it kinpira-style or finely chopping it to mix into fried rice.

In the current study, the dietary fiber concentration of broccoli stems was lower than that of the florets. Still, using edible stems instead of discarding them is meaningful. It's not about winning a "nutritional contest" with the florets.

Regarding kiwi skin, Zespri, the distributor, also advises that it can be eaten if washed well. If the feel of the fuzz bothers you, you can adjust how you eat it, such as slicing it thinly.

However, people with a kiwi allergy should not try this. If you feel discomfort when eating, there's no need to force it for the sake of nutrition.

Start by slightly increasing the usable parts of one ingredient. That level of beginning is sufficient.

Some foods should not be expanded to "eat whole"

It's important not to apply this concept to all vegetables and fruits.

A typical example is potatoes. According to the Ministry of Agriculture, Forestry and Fisheries, the sprouts and their bases, especially around the green skin, contain high levels of natural toxins like solanine and chaconine.

Sprouts should be removed down to the base, and green parts should be thoroughly removed, including the surrounding area. If the center is green, it should not be eaten. It's not safe to assume that heating will make it okay, as normal boiling does not guarantee detoxification.

However, it's not uniformly dangerous to cook with skin-on potatoes that have been properly cultivated and managed. It's important to assess the condition of the ingredient.

Additionally, the Ministry of Agriculture, Forestry and Fisheries advises against consuming loquat seed powder due to cyan compounds that may produce cyanide in the body.

Avoid the idea of grinding usually uneaten seeds for consumption based solely on "seeds are nutritious" or "it's easier to eat when powdered." The amount of dietary fiber alone cannot determine the safety of that part.

Washing doesn't make everything safe

Even for foods that can be eaten with the skin, washing well before eating is fundamental.

However, washing is not a method that solves all problems. Washing the surface alone may not remove toxins naturally contained in plants.

According to the researchers introduced by WELT, further examination is needed regarding pesticides, heavy metals, and natural harmful components. The measurement results showing high dietary fiber do not guarantee the safety of daily consumption amounts or cooking methods.

For foods like pineapple, where the skin and core were included in the research, it's not recommended to eat the hard skin just because it was analyzed.

When trying at home, choose parts that have been confirmed edible and for which cooking methods are known. For newer ways of eating, it's important to check not only "is it nutritious" but also "how can it be eaten safely."

Don't make the effort to use everything a burden solely on households

The perspective of this research extends beyond just home cooking.

Researchers are also calling on restaurants and food manufacturers to reevaluate the vegetable and fruit scraps generated daily. King's College London is also introducing menus that focus on utilizing more parts, known as "Root-to-Tip."

In places where the same ingredients are handled in large quantities, there is room to increase usable parts while considering processing methods, texture, and safety.

There are also limits to researching each peel or seed and increasing cooking effort at home. If the ready-made dishes or cafeteria meals usually purchased are utilized in a delicious way, it becomes easier for consumers to adopt.

It's a challenge posed by the research to reflect "not wasting" in the way dishes and products are made, rather than leaving it solely to individual effort.

Think once before discarding, but you don't have to eat everything

The concept of using up vegetables and fruits is not entirely new to Japan. Making kinpira with peels or using stems and leaves in soups are familiar practices in home cooking.

This research could serve as an opportunity to reevaluate such practices from the perspective of dietary fiber.

However, setting the goal too much on using everything up can lead to forcing oneself to eat hard parts or textures one dislikes or reaching for seeds whose safety is unknown.

In tomorrow's cooking, try keeping a bit of the broccoli stem you usually discard. Cut it into easy-to-eat pieces and add it to your usual stir-fry.

Such small changes might allow you to continue without losing the joy of dining. The important thing is not to reduce waste to zero but to refocus on the delicious usable parts of the ingredients you bought.

Sources and References

1. WELT: Article dated November 10, 2026. Research subjects, fiber comparison, survey of 40 people, researchers' views on safety.
   https://www.welt.de/gesundheit/article6ae7043e4b901a24d5d47a6d/ernaehrung-schalen-und-kerne-von-obst-und-gemuese-mitessen-was-spricht-wissenschaftlich-dafuer.html

2. King's College London: Official announcement of the research institution. Results of 10 out of 12 types, watermelon rind measurement, research positioning, and cafeteria initiatives confirmed.
   https://www.kcl.ac.uk/news/eating-root-to-tip-could-help-your-health-and-the-planetKing's College London

3. Bibliographic information of the original paper: A paper dealing with the fiber of discarded parts during food preparation and the awareness of UK consumers. The content explanation is based on the provided article and university announcement, as the full text was not obtained from the publisher's site.
   https://doi.org/10.1080/09637486.2026.2734852kclpure.kcl.ac.uk

4. Zespri Official: Information on eating kiwi skin, washing, and cutting methods. Information from the distributor.
   https://www.zespri.com/ja-JP/blogdetail/can-i-eat-the-skin-of-kiwifruitZespri Official

5. Ministry of Agriculture, Forestry and Fisheries: Q&A on natural toxins in potatoes. Removal of sprouts and green parts, heating limits, and handling of skin-on dishes.
   https://www.maff.go.jp/j/syouan/seisaku/solanine/potato_alkaloid_QA.htmlmaff.go.jp

6. Ministry of Agriculture, Forestry and Fisheries: Warning about loquat seed powder and cyan compounds.
   https://www.maff.go.jp/j/syouan/seisaku/foodpoisoning/naturaltoxin/loquat_kernels.htmlmaff.go.jp

7. Reddit: Posts on the