Apple Seeds

Even though apples are very nutritious, you should not eat apple seeds due to the presence of cyanide containing compounds. Some believe that there are medicinal benefits to apple seeds and you can even purchase apple seed extract. There are claims that apple seeds may treat cancer, hyperthyroidism, and even head lice. Although eating many apple seeds at a time may not be safe, they are a good source of potassium, magnesium, and are high in protein according to the "International Journal of Food Sciences and Nutrition."

Vitamin B17

Even though apples are very healthy, they are high in the compound amygdalin, sometimes known as vitamin B17, which is a potentially toxic cyanide-containing molecule. Side effects of toxicity of this compound include headache, nausea, fatigue and lethargy. The molecule was for many years believed to have anti-cancer properties, but recent studies have disputed these claims. A clinical trial was published in the "New England Journal of Medicine" finding that amygdalin was potentially toxic and not suited for cancer treatment.