Macadamia nuts are a dietary source of monounsaturated fatty acids, or MUFAs, (including palmitoleic and oleic acids) and soluble fiber, as well as copper, manganese and thiamin (vitamin B1). Macadamia nuts and their components have been shown to have antimicrobial, antioxidant and anti-inflammatory activities and may improve cholesterol profile and other markers of coronary artery disease.
While tree nuts generally are good sources of numerous phytochemicals, the phytochemical content of macadamia nuts appears to be comparatively low. Macadamia nuts have the highest oil content of any nuts, and much of the interest in this food concerns the impact of its oils on health. Macadamia nuts have low levels of omega-6 fatty acids and a favorable omega-6/omega-3 fatty acid ratio. Approximately 15% of the fatty acids in macadamia nuts are saturated fatty acids.

Breast cancer-related effects of eating macadamia nuts

There are no available epidemiological studies that isolate the possible impact of macadamia nut consumption on the risk of cancer for U.S. or European populations. In the absence of population studies, it is difficult to establish the likely impact of macadamia nut consumption on breast cancer risk and survival.
Existing studies concerning macadamia nut component fats have inconsistent conclusions. For example, oleic acid, which is also an important component of virgin olive oil, has been found to suppress HER-2/neu overexpression and to enhance the breast cancer growth-inhibitory effects of Herceptin. On the other hand, oleic acid has also been found to be associated with increased breast cancer cell proliferation and incidence. Nevertheless, since population studies have demonstrated that virgin olive oil has a protective effect against the risk of breast cancer (indicating that other components of olive oil may act synergistically with oleic acid to help prevent breast cancer or that the protective effect may be due to other components entirely), we are comfortable recommending it.
Palmitoleic acid, the most prevalent fatty acid in macadamia nut oil, is an omega-7 monounsaturated fatty acid that was found in one 2009 study to be associated with lower risks of benign fibrocystic breast disease and breast cancer. However, palmitoleic acid also has been associated with higher risk of breast cancer.

Additional comments

Macadamia nut oil has a high smoke point, so that it can be used as a cooking oil. Despite the high caloric and fat content of nuts, adding a moderate amount of nuts to the diet has been shown not to result in weight gain.
Below are links to recent studies concerning this food. For a more complete list of studies, please click on macadamia nut.