The Paleo diet is based on foods that humans evolved to eat and, therefore, excludes all processed foods as well as grains, legumes and dairy products. The Paleo diet is based on the consumption of grass-fed meat, free-range fowl and eggs, wild-caught fish, seasonal fruits and vegetables and fats from coconut oil, olive oil, avocado as well as some nuts and seeds. As for peanuts, they are actually not a nut, but rather a legume; legumes are not part of the Paleo diet.
The Paleo diet does not recommend the consumption of high amounts of polyunsaturated fatty acids and indicates that among the foods containing polyunsaturated fatty acids, a good ratio between omega-6 and omega-3 fats should be maintained. Too much omega-6 and too little omega-3 is associated with an increased risk of developing chronic diseases such as cancer, cardiovascular diseases and autoimmune and inflammatory diseases, as noted in an October 2002 article in "Biomedicine & Pharmacotherapy." It is estimated that humans evolved on an omega-6 to omega-3 ratio close to one to one, while the typical Western diet now provides 15 to 16.7 times more omega-6 than omega-3. Peanuts contain high amounts of omega-6 fats, which can skew your omega-6 to omega-3 ratio towards the wrong direction.
The thyroid is a gland mainly responsible for regulating the body's metabolism. If its function is impaired, it can lead to hypothyroidism, a condition characterized by weight gain, fatigue and depression. Many foods can interfere with thyroid function such as soy-based products, cruciferous vegetables, flaxseeds, turnips as well as peanuts and peanut butter. People diagnosed with, or suspecting that they have, hypothyroidism should refrain from eating peanuts, whether it is peanuts or any foods containing peanuts as part of its ingredients.
Alfatoxins constitute a toxic metabolite produced by certain fungi, which are microorganisms like molds that mainly grow in or on peanuts, corn and cottonseeds. Alfatoxins are carcinogenic, which means that they are capable of causing or promoting cancer. Alfatoxins levels tend to increase with the shelf life of peanuts or peanut-containing foods. The USDA tests for levels of alfatoxins in foods and allows low levels as the FDA believes that eating small amounts of alfatoxins does not cause health problems. However, considering the lack of data with long-term studies evaluating the impact of exposure to alfatoxins from peanuts over a lifetime, Paleo dieters are encouraged to avoid this legume.
Grains and legumes contain lectin, a glycoprotein substance able to bind with the gut wall and alter its permeability to enter the bloodstream. Lectins found in peanuts may, therefore, be associated with gastrointestinal problems such as Crohn's disease, celiac disease, colitis and irritable bowel syndrome, as well as allergies and autoimmune diseases. Because of these potential health problems, the Paleo diet recommends excluding peanuts from the diet.