Naturopath Dr. Peter D’Adamo of Eat Right for Your Blood Type fame believes each ABO blood group has a set of specific foods which boost immune function and decrease disease susceptibility, acting like locks on health while other foods could unlock it, leading to sickness, pain or disease. He theorizes that specific foods could protect immunity while others could lead to illness, pain or disease.

People with Type O blood, the oldest of the groups, tend to thrive when following a high-protein diet consisting of lean meat and vegetables with olive oil as the focus. This is thanks to higher secretion of two chemicals in their digestive tract which aid in digesting protein and fats; however, grains containing lectins aggravate their immune systems leading to unnecessary inflammation and autoimmune conditions. Type Os should also avoid eating cured meats due to sodium nitrite content as this could trigger unwanted inflammation; small meals more frequently as well as non-acidic red wines (lager or red wines that do not acidity), teas or herbal infusions for maximum benefits.

People with Type AB blood, the rarest ABO blood type, should consume a diet rich in moderate-protein, low glycemic index foods like fish, poultry, certain beans, fruits vegetables and dairy. Their digestive enzymes work similarly to Type O’s but their immune systems may be more sensitive to lectins in grains that bind with immune cells leading to inflammation or even autoimmune diseases; eating foods specifically tailored for this blood type such as licorice root eggs venison may help mitigate their effect.