Probiotics are living micro-organisms that may be able to help prevent and treat some illnesses. Promoting a healthy digestive tract and a healthy immune system are their most widely studied benefits at this time. These are also commonly known as friendly, good, or healthy bacteria.

Any part of the egg can harbor bacteria, and both whites and yolks have been implicated in food-borne illnesses (e.g. salmonella), however, the yolk is the most common source, according to the USDA. Egg yolks are also a source of dietary cholesterol, the bad type.

Allergy is one reason why an individual may opt for a soy-free diet. Food allergies involve the body’s immune system. Moreover, the phytoestrogens present in soy bind to estrogen receptors and exert both estrogenic and anti-estrogenic effects, phytoestrogens can inhibit thyroid peroxidase, the enzyme responsible for converting T3 to T4 (the exact clinical consequences of this are unknown, but several reports attribute thyroid cancer and goiter development to soy intake).

Gluten is a protein found in wheat, barley, rye, and sometimes oats. It’s perfectly natural, but people with coeliac disease, gluten intolerance, or the much less-common skin condition dermatitis herpetiformis, can have nasty reactions if they eat it.

Nuts are among the foods most commonly associated with allergic reactions. Allergies are different from intolerances and involve an immediate immune response upon exposure to the allergen. Symptoms include rashes, hives, asthma attacks or inflammation and in severe cases breathing or circulation problems. A nut-free diet is mandatory for people with allergies and nut-free schools.