According to Peter J. D'Adamo, the naturopath who created the Blood Type diet, type O people are descended from ancient hunters and should follow an eating plan that mirrors that of their ancestors: high in animal-based protein and vegetables, low in grains and dairy. Only certain fruits are considered good for type O. However, a University of Toronto study published in 2014 found no evidence to support the theory behind the Blood Type diet. Talk to your doctor about possible drawbacks before attempting to follow the plan.
Pick Fresh Plums
All types of fresh plums -- red, green or dark purple -- are good fruits for type O people to eat on the Blood Type diet, according to D'Adamo. The official Blood Type diet site says this is because plums contain components that may inhibit your body's ability to produce polyamines. A high blood concentration of polyamines, contends D'Adamo, can increase your risk of digestive problems and cancer. He also claims plums can lower a type O individual's level of excreted indican. High urine indican often occurs in people with digestive disorders.
Prunes, or dried plums, are also recommended by D'Adamo for type O individuals. Like fresh plums, the Blood Type diet touts the ability of prunes to lower polyamine synthesis and indican levels. Prunes are especially recommended for blood type O diabetics on the plan. Prune puree -- which you can prepare yourself or purchase -- is also allowed. It can be used as a substitute for butter or oil in baked goods for far less fat and cholesterol. Plan on 1/4 cup of prune puree for every 1/4 cup of fat.
People with type O blood can include plenty of fresh and dried figs in their diet. Both purportedly have the same effect on indican and polyamine levels as plums and prunes. Avoid candied figs or figs canned in heavy syrup, both of which contain high levels of sugar. While 1 cup of sliced fresh figs counts as a single serving of fruit, only 1/2 cup of dried figs is considered a full serving. Limit your intake of dried fruits to avoid excess calories.
Other Allowed Fruits
Blood type O people can eat a number of other fruits that are considered neutral for them on the Blood Type diet. Based on the diet's premise, these fruits are not harmful, but do not have the same specific medical benefits for type O people as figs, prunes and plums. They do, however, provide fiber and essential nutrients like potassium and vitamin C. Some examples appropriate for blood type O individuals include cherries, apples, all varieties of grapes, watermelon, pears, bananas, blueberries, lemons, grapefruit, papayas and raspberries.