Raspberries' most peculiar nutrient is ellagic acid, a natural phytonutrient belonging to the family of tannins, which is probably the most important antioxidant found in raspberries. Ellagic acid is frequently sold in health food stores as a dietary supplement.
Ellagic acid, as well as all the other antioxidants found in raspberries, are useful to prevent damage to cell membranes and DNA, since they prevent the action of free radicals by quenching their oxidant potential.
Other important phynutrients contained in raspberries are flavonoids: the most represented are quercetin, kaempferol and two cyanidin-containing molecules, cyanidin-3-glucosylrutinoside and cyanidin-3-rutinoside.
These two latter molecules belong to the family of anthocyanins, important pigments that are responsible for the color of raspberries and other berries.
Anthocyanins are not only pigments though, they also possess important antioxidant properties, and research has proven that they also work as antimicrobic agent both against bacteria and fungi.
Further research is being conducted, and preliminary results show that raspberries probably have cancer-protecting properties: berries appear to inhibit cancerous cell proliferation in animals diagnosed with cancer, that have been eating a diet rich in raspberries for at least 3 weeks.
According to research conducted in Netherlands, subsequently published in the journal Biofactors, the antioxidant content in raspberries is particularly high, clocking in at 50% higher than strawberries (a formidable antioxidant powerhouse themselves), up to three times higher than kiwifruit, and ten times higher than lycopene-rich tomatoes.
Their high content in antioxidants is probably due to the presence of ellagitannins: these compounds are particularly exclusive to the raspberry, and have been reported to have important anti-cancer activity. By exclusion, ellagitannins may provide up to 65% of the total antioxidant capacity of raspberries, with another 20% provided by Vitamin C (ascorbic acid), which is contained in quantities of 30mg per 100g.
The remaining 25% consists of anthocyanins (in particular pelagonidin glycosides and cyanidin).
Research has also observed that correctly frozen raspberries do not lose significant quantities of these important antioxidants (but processed raspberries do, so you should always prefer fresh berries to processed foods). The only exception appears to be vitamin C, which is approximately halved by the freezing process. If you correctly follow our freezing guidelines you'll add vitamin C in the form of lemon juice, which is a common trick to both preserve their antioxidant content and keep a bright color.
While discovering all these new and peculiar phytonutrients is cool, we shouldn't forget about traditional nutrients, especially vitamins.
Raspberries are an excellent source of vitamin C, manganese, folate, riboflavin, magnesium, niacin, potassium and copper. This makes them a very good source of B class vitamins, as well as an excellent source of soluble dietary fiber.
A study published in the Cancer Letters showed that diets high in fruits (in particular, raspberries, blackberries and muscadine grapes) reduce the risk of developing cancer by inhibiting metalloprotease enzymes: these enzymes are normally present in moderate quantities, and are needed by our bodies to successfully develop tissues. If they're produced in excessive quantities they are an important cause of cancer development, since they aid cancerous cells in invading other tissues.
A study published in the Archives of Ophtalmology involving 110,000 subjects of both sexes evaluated the effects of consuming fruits, vegetables, antioxidant vitamins such as A,C and E and carotenoids on the risk of developing Age-Related Macular Degeneration.
Macular Degeneration is the primary cause of sight loss in adults, and the study found that by eating at least 1.5 servings of fruits daily, one can reduce the risk of developing the disease by 36%.
Risk reduction was not directly linked to consumption of vegetables, antioxidants and vitamins, but to the consumption of whole fruits: the optimal level, according to the study, is three servings a day, which can be easily reached by sprinkling raspberries on your morning cereal or dressing up salads with other fruits.