Some common allergy triggers are milk, shellfish, legumes, sesame, eggs and tree nuts like almonds and walnuts.

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Statistically, it amounts to big business: the Golden State, with the largest agricultural sector in the nation, produces more than 250 commodities, from almonds to walnuts, and leads the nation in 75 of them (almost all of America's grapes and dates, and more than three-quarters of its strawberries and lettuce, come from California).

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The group that consumed more nuts was asked to eat a combination of 30 grams of walnuts, almonds and hazelnuts every day.

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Mountains of walnuts, almonds and pistachios.

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The other was told to eat 30 grams of nuts (walnuts, almonds and hazelnuts) every day. (The participants were given the olive oil and nuts.) The control group was told to follow a low-fat diet consisting of fruits, vegetables, low-fat dairy products, bread, pasta and fish.

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