Macadamia is native to the subtropical rainforests of northeastern Australia, where Aboriginal Australian peoples gathered and ate the nuts for thousands of years before European colonization. It carries the distinction of being one of very few native Australian food plants to become a globally significant commercial crop, with Hawaii — not Australia — becoming its largest modern producer following its introduction there in the late 19th century.
Macadamia's exceptionally high fat content (the highest of any commonly consumed nut) initially made it seem like an unlikely candidate for heart-healthy claims, until research began focusing on the specific type of fat it contains — predominantly monounsaturated fat.
Macadamia has real but population-dependent evidence for cholesterol. An earlier randomized, crossover, controlled feeding study in 25 mildly hypercholesterolemic adults found a macadamia-rich diet significantly reduced total and LDL cholesterol compared to an average American diet, and a separate supplement trial similarly found significant reductions in total cholesterol and LDL alongside an HDL increase in hypercholesterolemic men.
A more recent randomized trial (the MAC Study) in overweight and obese adults found only non-significant reductions in total cholesterol and LDL, with researchers noting cholesterol-lowering effects were modified by body composition — greater benefit occurred in people who were overweight rather than obese, and in those with lower body fat percentage. This population-dependent pattern is a genuine, meaningful nuance, and is why "Limited-Moderate" (rather than "Strong," as with walnut, almond, or pistachio) is the accurate rating.
Eaten raw or roasted, shelled; ground into butter or pressed into oil in some preparations.