Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder, meaning it is a problem caused by changes in how the GI tract works. People with a functional GI disorder have frequent symptoms, but the GI tract does not become damaged. IBS is not a disease; it is a group of symptoms that occur together. The most common symptoms of irritable bowel syndrome are abdominal pain or discomfort, often reported as cramping, along with diarrhea, constipation, or both. In the past, irritable bowel syndrome was called colitis, mucous colitis, spastic colon, nervous colon, and spastic bowel. The name was changed to reflect the understanding that the disorder has both physical and mental causes and is not a product of a person's imagination.

Vitamin D toxicity, also called hypervitaminosis D, is a rare but potentially serious condition that occurs when you have excessive amounts of vitamin D in your body. Vitamin D toxicity is usually caused by megadoses of vitamin D supplements — not by diet or sun exposure. That's because your body regulates the amount of vitamin D produced by sun exposure, and even fortified foods don't contain large amounts of vitamin D.

Cancer is the second leading cause of death in the United States. About one-half of all men and one-third of all women in the US will develop cancer during their lifetimes. Today, millions of people are living with cancer or have had cancer. Cancer begins when cells in a part of the body start to grow out of control. There are many kinds of cancer, and different types of cancer respond to different types of treatment. The growth in our knowledge of cancer biology has led to remarkable progress in cancer prevention, early detection and treatment. Scientists have learned more about cancer in the last two decades than has been learned in all the centuries preceding.