Your gastrointestinal (GI) tract is the tube that goes from your mouth to your anus. The GI tract includes your esophagus (food pipe), stomach, and small and large intestines. Your small intestines are where food is absorbed. Good bacteria live in your intestines. You need the right amount of these good bacteria.
What is bacterial overgrowth syndrome?
Bacterial overgrowth is when the good bacteria in the small intestines grow too much. The extra bacteria keep you from absorbing all the nutrients in your food. Not absorbing nutrients is called malabsorption Overview of Malabsorption Food you eat has to be digested before it can go into your body. Digestion breaks food down into its separate parts: Proteins Fats Carbohydrates Proteins, fats, and carbohydrates are nutrients... read more .
The extra bacteria in your intestines keep you from digesting food properly
The bacteria also use up nutrients in your food that you need for your health
Some people have no symptoms, but others have diarrhea, lose weight, or feel gassy and bloated
Doctors may do a breath test, test samples of fluid from your small intestine, or do x-rays of your GI tract
Doctors treat bacterial overgrowth syndrome with antibiotics and may suggest changes in your diet
What causes bacterial overgrowth syndrome?
Bacterial overgrowth syndrome is mainly caused by:
Conditions that slow down your GI tract, which keeps your intestines from flushing out extra bacteria
The most common cause of a slow-down is:
Other diseases that can cause a slow-down include an underactive thyroid Hypothyroidism Your thyroid is a gland below the Adam’s apple in your neck. Your thyroid releases thyroid hormones. The hormones control how fast your body’s chemical functions work (metabolic rate). Almost... read more (hypothyroidism), systemic sclerosis Systemic Sclerosis Systemic sclerosis causes scarring in your skin, joints, organs, and blood vessels. Systemic sclerosis is rare It is more common in women than in men and usually happens in people ages 20 to... read more 
, and amyloidosis Amyloidosis .
Certain types of surgery on your intestines and complications of surgery also can cause bacterial overgrowth.
What are the symptoms of bacterial overgrowth syndrome?
Some people have few symptoms or only weight loss.
Common symptoms are:
Diarrhea that is greasy and smelly
Belly pain
Bloating
Passing more gas than usual
Vitamin and mineral deficiencies can cause:
Easy bruising
Tingling of hands and feet
How can doctors tell if I have bacterial overgrowth syndrome?
Doctors diagnose bacterial overgrowth syndrome based on your symptoms and if you have conditions that favor overgrowth of bacteria in your colon. They may also:
Look down your stomach and intestines with a flexible viewing scope (endoscopy)
Measure certain chemicals in your breath
Take x-rays of your stomach after you swallow a liquid contrast agent X-rays with a radiopaque contrast agent X-rays are high-energy radiation waves that can penetrate most substances (to varying degrees). In very low doses, x-rays are used to produce images that help doctors diagnose disease. In high... read more
How do doctors treat bacterial overgrowth syndrome?
Treatments can include:
Antibiotics
Eating less carbohydrates and fiber
Vitamins or minerals to correct specific deficiencies
Most people get better after taking antibiotics for 10 to 14 days.
Doctors may suggest you eat a diet that's higher in fat and lower in carbohydrates and fiber to slow down the bacteria's regrowth.
