Nutritional value of berries
Finland’s forests produce an abundance of nutrient-rich, flavourful foods that can be gathered for free. Wild berries are an important part of our daily diet. Increased consumption of berries is recommended because they contain more vitamins, minerals, trace elements, and polyphenols (a compound with numerous health benefits) than many fruits.
When berries are in season, copious amounts are available. Berries can be enjoyed year-round by freezing them, or preserving them for winter in the form of jam or juice. For the most part, berries should be processed as little as possible so that they retain most of their nutrients when eaten. The highest levels of healthy polyphenol compounds are found in the skin of berries, so it is a good idea to use the leftover material from making juice to prepare other foods.
Berries can be included in every meal of the day in various forms – whole, fresh, dried, or crushed, or as berry powder or juice. Different types of berries can be added to various dishes.
Eat 100 grams of berries every day!
Berries are one of the most nutrient-rich foods: they have a high proportion of nutrients relative to energy content. Berries are a light, low-calorie food with an energy content of approximately 35–80 kcal/100 g. They consist mostly of water (80–90%). The carbohydrates in berries are natural berry sugars: glucose, fructose and sucrose. Berries also contain small amounts of sugar alcohols, such as sorbitol.
The protein and fat content of wild berries is low. Sea buckthorn berries are an exception, having a fat content as high as 5 g/100 g. The oils in berry seeds, and also in the flesh of sea buckthorn berries, have a composition that confers many health benefits. The smaller the seeds of the berry are, the higher the oil concentration. Seed oil mainly contains polyunsaturated fatty acids. It is high in essential fatty acids that the body needs and can obtain only from foods, linoleic (omega 6) and alpha-linolenic (omega 3) acids in an advantageous 1:1 ratio. In addition to essential fatty acids, sea buckthorn also contains monounsaturated fatty acids: oleic acid, in the omega 9 family, and palmitoleic acid, in the omega 7 family. Being a part of the plant kingdom, berries contain no cholesterol.
Most wild berries are good sources of dietary fibre and contain more fibre than fruits do, both in soluble and insoluble form. Pectin, a soluble fibre, serves as a building block for the cell walls of plants. Berries contain more pectin before they are quite ripe, a fact used to advantage when making jams and jellies. Berries with thick skin that naturally contain high quantities of pectin compounds require less pectin to be added for gel formation. High-fibre foods have a fibre content of at least 6 g/100 g, so cloudberry and sea buckthorn are wild berries that are especially good sources of fibre.
Vitamins, minerals and trace elements
Berries are one of the most important sources of vitamin C in our diet. Of the wild berries, sea buckthorn and cloudberry are especially rich in vitamin C. Just 75 grams of cloudberries or less than 50 grams of sea buckthorn berries satisfies the recommended daily allowance of 75 mg of vitamin C. Bilberries and lingonberries are not considered to be among the best sources of vitamin C, but are equally rich in various polyphenol compounds. Vitamin C is water-soluble and easily degraded by oxygen, light, and heat, so berries are at their most nutritious when fresh and uncooked.
Wild berries are also a good source of vitamin E. Cloudberry and sea buckthorn have large amounts of seed oil, so they also contain more fat-soluble vitamin E (about 3 mg/100 g) than the other wild berries. The seed oil of sea buckthorn contains as much as 250 mg/100 g of several different kinds of natural vitamin E compounds, the tocopherols and tocotrienols. Vitamin A in berries occurs in its precursor form, carotenoids.
Aside from vitamins, berries also contain minerals and trace elements in amounts comparable to fruits and vegetables. These include potassium, calcium, iron, magnesium, zinc, selenium, and manganese. The amounts are not large enough for berries to be considered a significant dietary source of minerals or trace elements, however. Berries have a high potassium to sodium ratio, which also makes them a suitable food for people with high blood pressure.
Besides vitamins and minerals, berries contain polyphenols, which are not actually classified as a nutrient. These compounds perform many important and beneficial functions in the plants themselves, such as regulating their growth and protecting them from excessive UV radiation, insect pests, viruses, bacteria and fungi. Temperature, light, and the nutrient and moisture content of the soil are some of the factors that affect the quantity of polyphenols developing in plants. Polyphenols are the subject of intensive research and have been found to have beneficial effects on human health as well. Wild berries are one of the best sources of polyphenols in our diet and also contain more of these compounds than any other plant. Each kind of berry typically produces certain polyphenols.
Anthocyanins are phenol compounds of a strong red, blue, or purple colour that are found in the cell sap of plants. The colour of a berry is an indicator of its anthocyanin concentration. Dark blue berries like bilberry, crowberry, blackcurrant and bog bilberry have the highest anthocyanin content. Red berries have lower quantities of these compounds. Yellow and colourless berries have very low quantities or none at all. Anthocyanin levels in wild bilberry are 4–5 times higher than in cultivated highbush blueberry. There is interest in using anthocyanins extracted from berries as a food colouring instead of synthetic anthocyanins.
The flavonoid portion of anthocyanin is called anthocyanidin. In anthocyanin, a sugar is attached to the flavonoid portion (anthocyanin = anthocyanidin + sugar). Anthocyanidins on their own are unstable, but the sugar component makes them more stable. This explains why they occur in combination with sugars, as anthocyanins, in plants.
Flavonol compounds include quercetin, myricetin, kaempferol and isorhamnetin. Bog bilberry, sea buckthorn, and cranberry have the highest levels of flavonols, mainly quercetin.
Resveratrol, a derivative of stilbene, is found in high quantities in dark grapes. Lingonberries, too, contain comparable amounts of resveratrol.
Lignans are phenolic phytoestrogens that are converted to enterolactone by intestinal bacteria in the human body. Lingonberries and cranberries contain significant amounts of lignans, nearly 50% more than most of the other wild berries. It has been suggested that lignans suppress the development of hormone-dependent cancers.
Tannins include ellagitannin and proanthocyanidin compounds. In studies, ellagitannin has been observed to inhibit the growth of harmful intestinal bacteria such as Salmonella, Staphylococcus, and Campylobacter. Ellagitannins do not have an impact on the growth of beneficial intestinal bacteria. The highest ellagitannin levels are found in berries that are aggregate drupes (cloudberry, raspberry, and arctic raspberry). Strawberry also contains some ellagitannin. These berries are the main source of ellagitannin in the diet, since the compound does not occur in other regularly consumed foods to any significant extent. Cranberry and lingonberry contain considerable amounts of proanthocyanidins. Proanthocyanidins have been observed to inhibit the growth of harmful bacteria in the walls of the urinary tract, the gastric mucosa, and the mouth.
Polyphenol compounds in berries:
- Flavonols: bog bilberry, sea buckthorn, cranberry, lingonberry, crowberry
- Flavanones: sea buckthorn
- Catechins: lingonberry, crowberry, bilberry
- Anthocyanins: bilberry, crowberry, bog bilberry
- Phenolic acids
- Hydroxycinnamic acids: bilberry, cloudberry
- Hydroxybenzoic acids: bilberry
- Lignans: lingonberry, cranberry, bilberry
- Ellagitannins: cloudberry, raspberry, arctic raspberry
- Proanthocyanidins: cranberry, lingonberry
- Resveratrol: lingonberry
Berries and health
So far, indications of the effects that berries may have on health have mainly been obtained from in vitro studies (using test tubes or Petri dishes) and animal tests. In these studies, compounds found in berries have been observed to have mechanisms that prevent bacteria attachment (harmful intestinal bacteria, Helicobacter, bacteria that cause dental disease); effects on glucose, insulin, and lipid metabolism; and effects on inflammatory responses. In Finland, current research focuses on the effect of berries and the compounds in them on oral health and infections, metabolic syndrome, and blood sugar levels after meals.
Only limited information has been obtained so far from clinical nutritional studies on human subjects. This includes promising results on the prevention of urinary tract infections in studies of cranberry-lingonberry juice concentrate, and on health benefits for the skin and mucous membranes from sea buckthorn oil. Regular daily consumption of berries (160 g/day) has also been found to have a positive impact on blood pressure, HDL cholesterol levels, and platelet function. Additional evidence would be needed to demonstrate that anthocyanins have an effect on eye health or signs of aging.