Biology Reference
In-Depth Information
8.2.6 Walnuts
Walnut trees (
Juglans regia
) are cultivated in many European countries,
and the seeds are an excellent source of many nutrients. Compared to
other nuts, walnuts are unique due to their high content of α-linolenic
acid, an essential omega-3 polyunsaturated fatty acid. They also contain
non-flavonoid polyphenols, with the highest concentration found in the
thin tan-brown pellicle. The total content of phenols (as determined by
the Folin-Ciocalteu assay) in 50 g of shelled walnuts was 802 mg as
gallic acid equivalents (Anderson
et al.
, 2001). Daniel
et al.
(1989)
reported an ellagic acid content of 590 mg/kg of dry weight after acid
hydrolysis of
Juglans nigra
walnuts. Ellagic acid, valoneic acid
dilactone, pedunculagin and 15 other ellagi- and gallotannin compounds
have been identified from walnut kernels (Anderson
et al.
, 2001, Fukuda
et al.
, 2003, Cerdá
et al.
, 2005, Ito
et al.
, 2007).
8.3 Dietary Intake
The intake of phenolic acids, including ellagic acid, by Bavarian adults
was studied in Germany (Radtke
et al
., 1998). A database containing the
phenolic acid contents of foods (data from literature) was built and 7-day
dietary protocols of 63 women and 56 men of the German National
Food Consumption Survey were evaluated. The intake of ellagic acid
was 5.2 mg/day. Berries (strawberries, red raspberries) and nuts (walnut)
provided 38% and 54%, respectively, of the ellagic acid intake.
In the Finnish diet, strawberries, red raspberries and cloudberries are
the main potential sources of ellagitannins. The daily intake of total
ellagic acid (including ellagitannins and free ellagic acid) from berries
was calculated by using the food consumption data obtained from the
Finnish Household Survey 1990 (8258 households) and 1998 (4359
households). This survey records the purchase of foods for the
household. Fresh strawberries and cloudberries, but not raspberries, were
reported in the survey. In 1990 and 1998, strawberries and cloudberries
alone provided 5.8 mg (Häkkinen
et al.
, 2000) and 8.7 mg (Häkkinen
et
al.
, unpublished data), respectively, of ellagic acid per day per person.
The most recent estimation of intake is based on the compositional data
