Fraser et et al1 studied more than 26 000 white Seventh-Day Adventists from California for 6 years and found a possible protective effect of nut consumption on risk of fatal and nonfatal coronary heart disease events. Consumption of whole wheat bread and beef were associated with lower and higher than average risk, respectively, but these associations were weaker than that for nut consumption. Fraser et al and Castelli, in his editorial, raised the possibility that nuts contain "one or more active substances"1 or that there are "other factors associated with nut eating".2
I wish to call your attention to the possibility that differences in dietary copper may explain these associations. In general, nuts are high in copper,3 with peanuts, walnuts, and almonds ranging from 8 to 12 μg of copper per gram. Some of the hypercholesterolemic response to red meat may be due to poor copper
Klevay LM. Copper in Nuts May Lower Heart Disease Risk. Arch Intern Med. 1993;153(3):401–402. doi:10.1001/archinte.1993.00410030101021
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