English walnut - Juglans regia.
Black walnut - Juglans nigra.

The common or English walnut, which is native to areas stretching from the Balkans to China but is now widely grown in many other temperate areas, is one of the most important nut crops grown. Black walnut is native to the eastern United States. It is important for its timber, used in fine furniture, rather than for its nut, the flesh of which is tasty but surrounded by a hard, thick shell (outer husk) that makes the nut difficult to utilize.

Young fruits are pickled in vinegar. Frequently used in snack foods. Aka Persian walnut or English walnut, native to Middle East. Regains freshness if soaked in milk overnight.

High in alpha-linoleic (omega 3 fatty acid) and linoleic acid (polyunsaturated fatty acids). Reduces cholesterol levels.

Greeks and Romans used walnuts to cure headaches, because of the shape, which resembles the two halves of the brain.

Peanut and Tree nut allergic reactions coexist in one third of peanut-allergic patients; frequently occur on first known exposure, and may be life-threatening, requiring emergency treatment. Accidental ingestions are common, occur frequently outside of the home, and often require emergency treatment. (Sicherer 1998 ref.2362 9)

Nut oils may pose a threat to patients with allergy, depending on the method of manufacture and processing. (Teuber 1998 ref.4336 9)

Allergens/Function:

Allergens:
Jug r 1, a 2S albumin (Teuber 1998 ref.4569 7)
Jug r 2, a 2S albumin seed storage protein (Teuber 1999 ref.4562 8)
Jug r 3

A 7S globulin, a vicilin, a major allergen. (Teuber 1998 ref.4336 9)
Asero suggests that walnut does not express any Bet v 1-like allergen and should not be considered a birch pollen-related food.

Recombinant Jug r 2 was shown to bind serum IgE from 9 of 15 patients tested. (Teuber 1999 ref.4562 8)

Adverse Reactions:

IGE AND IMMUNE:
Allergic reactions. Anaphylaxis. Dermatitis. Asthma. Anaphylaxis. (Foucard 1997 ref.682 8) (Ewan 1996 ref.1625 0)

Food-dependant exercise-induced anaphylaxis - walnuts, peanuts. (Guinnepain 1996 ref.823 14) (Caffarelli 1996 ref.6604 1)

Ansero et al suggests that skin prick tests with commercial extracts of plum and walnut may be usefully employed to detect patients with Oral Allergy Syndrome (OAS) reacting against stable allergens. (Asero 1999 ref.2598 8)

Anaphylaxis to walnuts and pine nuts induced by ACE. (Moneret-Vautrin 1998 ref.4420 2)

Asthma due to Central American walnut (Juglans olanchana) dust. (Bush 1983 ref.2421 9)

Recurrent aphthous stomatitis. (Eversole 1982 ref.2755 0)

Crossreactivity.

NON IMMUNE:
The effects on iron absorption of nuts were measured in 137 Indian women. When the absorption from bread and nut meals (walnuts, almonds, peanuts, and hazelnuts) was compared with that from bread meals, the overall geometric mean absorption from the nut meals (1.8%) was significantly less than from the bread meals alone (6.6%). In contrast, coconut did not reduce absorption significantly. All the nuts tested contained significant amounts of two known inhibitors of Fe absorption (phytates and polyphenols) but the amounts in coconut were significantly less than in the other nuts. Fifty milligrams ascorbic acid overcame the inhibitory effects of two nuts that were tested (Brazil nuts and peanuts). This is different from that found previously for soy protein, another potent inhibitor of Fe absorption. (Macfarlane 1988 ref.7810 1)