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Researcher Anna-Maria Pajari recommends eating at least one to two decilitres of berries a day, saying that studies suggest these small natural chewables may even prevent cancer.

Anna Sievinen HS

Berries are a Finnish superfood.

The magic of bilberries, strawberries and other similar natural dainties lies especially in polyphenols, the phenolic compounds they contain,’ says Anne-Maria Pajari, associate professor of nutrition science. She has been studying the health benefits of berries for nearly 20 years.

Almost all plants form polyphenols. These bring the plants great benefits such as attracting pollinators and giving the berries their colour, protecting the plant from UV radiation and combating pests and plant diseases. Polyphenols are not nutrients like, say, vitamins.

Nevertheless, they have many health benefits for humans because they are antioxidants. These are types of compounds that inhibit the oxidation of cells. In other words, antioxidants prevent the cells from going rancid like fish spoiled by oxygen. This type of oxidation is constantly occurring in our bodies. So, antioxidants are ‘anti-rust agents’ that help your cells stay healthy.

The body itself produces a whole range of enzymes that act as antioxidants, but we also need to get them from our diet. Polyphenols are found especially in the skins of berry seeds. Berries also contain your essential nutrients Vitamins C and E. These act as antioxidants as well.

Can you tell by the colour how healthy a berry is to eat?

‘Polyphenols are a chemically diverse group with thousands of combinations and a great variety of health benefits. Many polyphenols are coloured, giving berries their characteristic colours. Blue-violet anthocyanin is found in bilberries, blackcurrants and, say, aubergine and red onion skins.

Lingonberries and cranberries are filled with red proanthocyanidin, while yellow cloudberries contain ellagitannin. There is no point in ranking berries according to colour. What is most important is to eat the widest variety of different coloured berries possible. This will maximise the health benefits. It is advisable to choose a most colourful array of vegetables for your plate as well. Although berries give health benefits largely through polyphenols, they are also rich in vitamins and fibres that are good for you. The highest fibre content is found in berries with lots of skin and seeds, like cloudberries and currants.’

How do polyphenols benefit your health?

‘Many studies on the health benefits of berries have been conducted in Finland. A few years ago, we did a study where we divided the subjects into two groups. Both groups ate the same amount of meat. However, one group also ate a mixture containing 200 grams of bilberries, lingonberries, cloudberries, raspberries, strawberries and blackcurrants daily for a month. We studied how this berry consumption affected intestinal metabolism. We also isolated faecal water from stool samples and exposed it to colon cancer cells.

Eating berries led to faecal water composition that suppressed cancer cell growth and altered intestinal metabolism in a cancer-preventive direction. So, this suggests that eating a lot of berries may prevent colon cancer. Another study, conducted by a group led by Professor Tuula Salo, scrutinised oral cancers in cell and animal models. The results show bilberries may prevent oral cancers.

Meanwhile, at the University of Tampere, Professor Eeva Moilanen led a study conducted in mice. The study found that lingonberries, bilberries and cloudberries reduced low-grade inflammation in the body. For example, obesity produces low-grade inflammation that can cause cardiovascular disease and type 2 diabetes. Eating cloudberries seems to be beneficial for the regulation of fat and sugar metabolism in particular.’ Berries help to control blood sugar levels after meals. They also lower cholesterol and improve intestinal comfort.

How many berries should you eat?

‘As of yet, we do not know the minimum effective dose needed to bring about health benefits. I recommend eating at least one to two decilitres of berries a day. How you like to have your berries is of little importance. For instance, our study subjects ate berries that had been frozen. Polyphenols are relatively temperature-resistant, and they can withstand some heating. Bringing your berry soup to a rapid boil will not destroy the polyphenols; but if you cook jam for hours on end, you will start losing some of them. Colour is a good sign. If the berries are losing their colour, the polyphenols are disappearing as well.’

Is it harmful to add sugar to berries?

‘No, a small amount of sugar is all right. It is much better to add a little sugar to your berries than to leave them uneaten. You will gain the health benefits of berries even if you add a little sugar. In Finland, salt is clearly a bigger problem than sugar. More than 90% of Finns get too much salt. This exposes them to high blood pressure and cardiovascular diseases.’

Published in Tiede Luonto 5/23.