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Wild berries: a good source of omega-3

Abstract

It has been reported that some wild green vegetables are good sources of α-linolenic acid (ALA, an essential omega-3 fatty acid). Using available data from the Norwegian food composition table, the present study shows that three common Nordic berries (blueberry, cloudberry and cowberry) on average contain 0.7 g of fat (=21% of total energy) and 0.25 g ALA (=36% of total fat) per 100 g, which is quite similar to what has been reported for the ALA-rich wild green vegetables. In addition, this study shows that a hypothetical replacement of 5% of Norwegian 8th grade girls’ diet, with a similar energy amount of wild berries, would significantly improve the diet – also improve intake of nutrients not commonly associated with berries.

Introduction

Polyunsaturated omega-6 (n-6) and omega-3 (n-3) fatty acids are essential fatty acids and must therefore be provided by the food. Both are needed for optimal human growth and development. However, it has been suggested that today we eat more n-6 compared to n-3 than what is beneficial (Simopoulos, 2002).

Well-known sources of n-3 fatty acids are fish and other marine animals, as well as linseed, walnuts and some vegetable oils (e.g. linseed and rape seed). However, several people find it easier to buy n-3 supplements, such as cod-liver oil and n-3 tablets.

Most fruits and vegetables are reckoned as low in fat content. However, all cells (plant and animal) are embedded in a cell membrane consisting of fatty acids, and several fruits contain edible fat-containing seeds. Compared to the total amount of energy offered, several fruits and vegetables contain ample amounts of fat.

What characterize several wild plants is that they contain much of the n-3 fatty acid α-linolenic acid (ALA). Purslane has been reported to contain 0.85 g of total fat and 0.41 g of ALA per 100 g, considerably more than cultivated leafy vegetables (Simopoulos and Salem, 1986; Simopoulos, 2004). Zeghichi et al. (2003) reported that two other wild leafy plants, molokia and stamnagathi, contain fat and ALA at levels similar to purslane. Guil et al. (1996) reported that 20 wild Spanish vegetables contained between 0.14 and 0.75 g fat per 100 g, and that between 10 and 55% of the fatty acids was ALA. Malainey et al. (1999) have reported fatty acid composition of several native foods (wild and cultivated) of Western Canada, and several species of greens and also some species of berries contained large proportions of ALA (35–40% of total fat content).

Here, I will first discuss that wild Nordic berries also do contain ample amounts of fat, and that they are good sources of ALA. Secondly, I will show how the diet of Norwegians will improve with a hypothetical 5E% (percent of total energy) substitution of the diet with wild berries.

Methods

The Norwegian food composition table (National Nutrition Council and Norwegian Food Safety Authority, 1995) was searched for wild edible plants. The inclusion criterion was that data on fatty acid composition were available. This criterion was met for only three wild plants; blueberry (Vaccinium myrtillus), cloudberry (Rubus chamaemorus) and cowberry (Vaccinium vitis-idaea). All three are common wild berries found in forests and mountains throughout large areas of the Nordic countries. They are all utilized as a food source, somewhat more in Finland than in the other countries (Nordic Council of Ministers, 2003).

These three berries are compared to the three most eaten fruits in Norway; apples (15% of the apples in Norway are domestic, 85% are imported), bananas (all imported) and oranges (all imported). Nonparametric analyses (Mann–Whitney U-test) are used to compare the wild berries to the commonly eaten fruits.

A total of 5E% of the diet of Norwegian 8th grade girls, data taken from the most recent dietary survey in Norway (Øverby and Andersen, 2002), was hypothetically replaced with a similar energy amount of a mix of the three wild berries (1/3 each). Calculations of nutrient contents of this new diet were made. Only the nutrients where these girls did not meet the recommended levels are included in the calculations: Norwegian 8th grade girls eat too much saturated fat (SAT) and added sugar, and they eat too little polyunsaturated fat (PUFA), fruits and vegetables, fibre, vitamin E, vitamin D, iron and calcium (Øverby and Andersen, 2002).

Results

The three wild berries contain on average 0.7 g fat (=21% of the total energy). The mean content of ALA was 0.25 g per 100 g of berries (=36% of total fat content), which corresponds to 1.3 g ALA/MJ.

Compared to the commonly eaten fruits (Table 1), the wild berries contain less carbohydrate, more fat, more mono- and polyunsaturated fatty acids, more n-6 and n-3 fatty acids, a lower ratio of saturated to polyunsaturated fatty acids, a lower ratio of n-6 to n-3 fatty acids and more than 15 times more n-3 fatty acids per unit of energy.

Table 1 Content of selected nutrients in three wild Nordic berries and three commonly eaten fruits

When 5E% of the diet was replaced by wild berries, the new diet contained the same amount of energy (Table 2). However, the 5E% berry-replaced diet contained less SAT, more PUFA, less added sugar, more fruits and vegetables, more fibre, more vitamin E, and more iron and calcium – but less vitamin D.

Table 2 Calculation of 8th grade girls’ diet if 5E% was replaced by wild berries

Discussion

The three Nordic wild berries do all contain ample amounts of fat, and they are also good sources of the n-3 fatty acid ALA. They contain ALA at similar levels as reported for purslane and other ALA-rich plants (Simopoulos and Salem, 1986; Guil et al., 1996; Malainey et al., 1999; Zeghichi et al., 2003; Simopoulos, 2004), which are much higher than for the commonly eaten fruits assessed in the present study. In addition, the wild berries contain an n-6/n-3 ratio of about 1, which has been suggested as an ideal ratio (Simopoulos, 2002), 4–6 times lower than today's Nordic diets (Nordic Council of Ministers, 2005). Compared to the energy they contain, wild berries contain n-3 fatty acids in the same amounts as fish do. Salmon (farmed, a fat fish), Sea wolf (an intermediate fat fish) and Cod (a non-fat fish) contain respectively 1.8, 1.3 and 0.6 g n-3/MJ (National Nutrition Council and Norwegian Food Safety Authority, 1995). However, the n-3 fatty acids of fish are much eicosapentaenoic and docosahexaenoic acids, which have somewhat different physiological properties than ALA (Crawford et al., 2000).

When measuring nutrient content per energy unit and not per weight unit, the results in the present study clearly shows that berries do contain much healthy fat. The wild berries also contain ample amounts of fibre, and of vitamins and minerals not usually associated with berries; vitamin E, iron and calcium. A hypothetical substitution of 5E% of the 8th grader's diet with berries clearly improved the diet's nutritional value (Table 2), an exception being vitamin D.

Only a few nutrients are assessed in this paper. These nutrients were chosen because they are consumed by the Norwegian girls in misappropriate amounts (Øverby and Andersen, 2002). Berries are in addition well known as excellent sources of vitamin C and of total dietary antioxidants. In a Norwegian study assessing total antioxidant concentrations in 124 plant foods, most of the plants with high levels of total antioxidants were berries (Halvorsen et al., 2002). An interesting point here is that the wild berries do contain more antioxidants than their cultivated cousins. Wild blackberries, blueberries, raspberries and strawberries contain on average 81% more antioxidants than the respective cultivated berries (Halvorsen et al., 2002).

Conclusion

Wild Nordic berries contain nutritionally significant amounts of fat and are good sources of the omega-3 fatty acid ALA. A higher consumption of wild berries would improve our diet.

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Correspondence to E Bere.

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Bere, E. Wild berries: a good source of omega-3. Eur J Clin Nutr 61, 431–433 (2007). https://doi.org/10.1038/sj.ejcn.1602512

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Keywords

  • berries
  • fruits
  • omega-3
  • α-linolenic acid

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