Most supporters of macrobiotics cite cases of patient’s personal experiences and testimonials to the effectiveness of macrobiotics but relatively few conventional studies have been able to verify these claims.

While there are many success stories that have been told by macrobiotic supporters, there are a number of strong exceptions.  Aveline and Lilly Kushi (wife and daughter of the father of American macrobiotics) were lifelong, dedicated practitioners of the macrobiotic lifestyle but both passed away as a result of cancer.  Renowned macrobiotics teacher Cecile Levin and macrobiotics speaker Dr. Anthony Sattilaro, both longtime macrobiotic practitioners, also passed away from cancer.  Even Michio Kushi, the student of George Ohsawa who brought macrobiotics to America has undergone an operation to remove a tumor in his intestine.

Several studies have been done which have shown that practitioners of the macrobiotic diet do indeed have a lower cancer risk than a traditional American diet.  However, each study also mentions that there is no indication that the macrobiotic diet has any additional benefit over the low-fat diets recommended by institutions like the ACS.  The reduction of breast cancer risk has been attributed to the well documented benefits of phyto-estrogens, which are consumed in much greater quantities in the macrobiotic diet.  Increased consumption of soybeans may have some effect on hormone-influenced cancers such as breast and prostate while avoiding processed foods limits the exposure to preservatives and pesticides that have an as-yet unestablished role in cancer.

 One area that has been documented extensively is the dangers of the macrobiotic diet in terms of adequate consumption of calcium, iron, zinc, vitamin B12, riboflavin, vitamin D, vitamin A and omega-3 fatty acids.  A well planned, balanced macrobiotic diet should be capable of including these nutrients at sufficient levels, however the more restrictive the diet, the more likely a deficiency in one of these nutrients will develop.  This facet of macrobiotics frustrates many oncologists, as many patients who choose to follow a macrobiotic lifestyle while receiving chemotherapy or radiation therapy do not receive adequate nutrition, which can exacerbate the known side effects of conventional therapy and is thought to lead to a larger than normal drop out rate.

 The macrobiotic diet is recommended against in children as a large study in the Netherlands showed statistically significant growth retardation in children who were raised on macrobiotic diets.  Additionally this study also found a psychomotor development delay in these same children also due to malnutrition.  Additionally, even if the diet was altered at a later point, only partial catch-up growth was noted in some areas while in others no catch-up growth was seen.  Therefore, children should not be on macrobiotic diets even for short amounts of time as this produces irreversible growth retardation.  This same study also noted decreased growth and development in babies born to mothers on macrobiotic diets, although the number of women followed was much smaller and the data less convincing.  Nevertheless, the study authors still recommend against pregnant or breastfeeding women following a macrobiotic diet.