Is your diet making you sick? If you're suffering from headaches, depression or hair loss, your food choices may be to blame

Before you blame your chronic headaches on stress or chalk up your constant colds to a weak immune system, you may want to examine your diet. "Many women think that pain or other symptoms, like mood swings and hair loss, are the result of a serious medical condition, when something far more simple is the cause: their eating habits," says Gail Frank, R.D., Dr.P.H., a professor of nutrition at California State University, Long Beach, and a spokeswoman for the American Dietetic Association. "It's important to remember that everything you consume will affect your body, from your skin to your digestive system." That's not to say symptoms like stomach cramps or depression don't warrant a doctor's visit. But before you schedule one, you'll want to take an inventory of what you've been eating--or not eating--and consider making an appointment with a dietitian too. (For a recommendation, visit eatright.org.) On the following pages, top medical and nutrition experts point out the links between six common problems and poor dietary habits, and tell you how to get your diet--and your health--back on track.

Problem Weakness, fatigue

Possible cause A low-calorie diet

Dipping below your daily calorie needs (more on that later) is a major health no-no. "Your body uses food as fuel," Frank explains. "If you're not eating enough, your system slows down and begins to burn muscle tissue for energy, which is a large part of why you may feel weak, tired or lightheaded." Experts suggest consuming 1,800-2,400 calories a day, depending on your height, weight and activity level.

Cure Visit Shape.com/calories to calculate your individual daily calorie needs. If you're trying to lose weight, talk to a dietitian about your eating habits, Frank advises. But keep in mind that no matter how much weight you want to lose, you should never drop below 1,200 calories a day.

When to see a doctor If you start eating more but still have a hard time performing everyday activities, such as walking or concentrating. You could have a virus such as Epstein-Barr or mononucleosis, or another serious condition such as depression.

Problem Mood swings, short-term depression, increased appetite

Possible cause A high-protein, low-carb diet

Consuming fewer than 50 grams of carbs a day can lead to a decrease in serotonin, the brain chemical that regulates both mood and appetite, according to two studies from the Massachusetts Institute of Technology in Cambridge. "A dip in serotonin means that you're more vulnerable to mood swings and even a depressed mood--and that you may not experience a 'full' feeling after eating," explains Judith Wurtman, Ph.D., MIT scientist and a co-author of both studies. "On the other hand, carbohydrates help stimulate serotonin production. After you eat them, your mood improves and you feel sated." If that isn't reason enough to jump off the low-carb wagon, a study from RVA University in Copenhagen, Denmark, shows that people on low-carbohydrate, high-protein diets report more muscle cramps, weakness and diarrhea than individuals on lowfat diets.

Cure To keep your blood sugar stable, preventing crashes that lead to mood swings and shakiness, eat a diet that's rich in complex carbohydrates (aim for at least five servings a day from sources like whole-grain pasta, brown rice and vegetables) as well as protein and unsaturated fats (found in fish, olive oil and nuts).

When to see a doctor If binge eating, mood swings or depression lasts more than two weeks, see a physician and/or psychologist, who can determine whether you have a more serious condition.

Problem Headaches

Possible cause Trigger foods

Headaches--believed to be caused by swelling blood vessels in the head--can be triggered by alcohol, caffeinated beverages, cheese, deli meats, chocolate, nuts, foods with MSG and even bananas, says David Buchholz, M.D., associate professor of neurology at Baltimore-based Johns Hopkins University and author of Heal Your Headache (Workman, 2002). "Some people [react] to chemicals in certain foods," he explains. "For example, tyramine [found in red wine and aged cheese] is a common irritant."

Cure Buchholz suggests that when a headache strikes, write down everything you've eaten that day. If your list contains one of the foods mentioned above, avoid eating it for several weeks. Then, slowly reintroduce it; if you eat or drink it again and your headache returns, you've found your culprit.

When to see a doctor If your headache is so painful and sudden that you can't function normally. Keep in mind that some people suffer from chronic headaches--often called migraines--for no apparent reason. A headache specialist can help determine the best course of treatment.

Problem Digestive troubles

Possible cause Not consuming enough fiber, or eating foods you can't tolerate

Women often blame gastrointestinal problems like pain, diarrhea and constipation on a "sensitive stomach," says Susan Lucak, M.D., a gastroenterologist and assistant professor of clinical medicine at Columbia-Presbyterian Medical Center in New York City. "More often than not, their diet lacks fiber, which cleanses the system and regulates bowel movements." Many women may not realize their stomach problems are the result of an intolerance, either to wheat or, more commonly, dairy: "Twenty-three percent of Americans can't digest lactose, the sugar found in milk. When they consume dairy products, they may experience bloating, gas or diarrhea," Lucak says.