There are hundreds of types of yeast, found in soil, on plant leaves and fruit, and in the sea. Yeast is used in food production and taken as supplements. But these tiny one-celled fungi are also naturally found in our bodies, where they can sometimes cause health problems.
Let’s be candid
Candida is a type of yeast present in healthy people. It is normally kept in check by bacteria and other organisms in the body. But illness or certain medications can cause Candida to overpopulate—a condition called candidiasis—and this can lead to vaginal infections, thrush (candidiasis in the mouth, which can occur in both men and women), and some skin infections. Most women in the U.S. get at least one vaginal yeast infection in their lifetime. People with weakened immunity, such as from chemotherapy or AIDS, are vulnerable to systemic fungal infections, which can be life-threatening. People who take steroids may also get various yeast infections. Despite popular belief, yeast infections are not related to diet—and there’s no evidence that eating or douching with yogurt cures them.
Vaginal yeast infections
The symptoms of vaginal yeast infections include a thick white discharge, pain during intercourse or while urinating, and an itching or burning sensation in the vaginal and often labial and vulvar areas. Over-the-counter antifungal medications are available, but you must be certain that what you have is actually a yeast infection. See your doctor for an initial diagnosis. The risk is that you may have something else—like a sexually transmitted infection (such as Chlamydia)—with similar symptoms that won’t be cured with these creams or suppositories. Studies have found that many women who think they have persistent yeast infections do not. Moreover, chronic use of these medications may cause Candida to become resistant to them. Recurring yeast infections may also be a symptom of diabetes or HIV infection, another good reason to be checked by a doctor. In some cases, prescription medication may be recommended.
Different fungi are usually to blame for jock itch—namely Trichophyton rubrum, the same fungus that causes athlete’s foot. It causes inflammation of the head of the penis (called balanitis), which may spread to the scrotum and perianal area. Men who are uncircumcised or have diabetes are more susceptible.
Many people think they are intolerant of or allergic to yeast, or that they have chronic low-level Candida infections, which they blame for their headaches, muscle pains, asthma, fatigue, weight gain, and mood swings. But there’s no evidence that yeast causes any of these problems, that “yeast-free” diets (which restrict sugars, breads, dairy products, alcohol, and other fermented foods) prevent or cure them, or that “chronic candidiasis” or “Candida hypersensitivity syndrome” exists, despite the claims made by some alternative medicine practitioners. While a few studies suggest there’s an association between overgrowth of Candida and irritable bowel syndrome, this remains controversial. True yeast allergies are very unusual.