What Are Probiotics?
The human body contains trillions of microorganisms—outnumbering human cells by a ratio of 10 to 1. Because of their small size, however, microorganisms make up only about 1 to 3 percent of the body's mass, but play a vital role in human health. Most of these microorganisms reside in the gut, and having the right balance of gut bacteria is linked to many health benefits, including weight loss, improved digestion, enhanced immune function, healthier skin and a reduced risk of many diseases.
Probiotics are a certain type of friendly bacteria that provide numerous health benefits when eaten. They are often found in yogurt, kefir, and other fermented foods like sauerkraut and kimchi, as well as in dietary supplements, and even beauty products. Although people often think of bacteria and other microorganisms as harmful “germs,” many are actually very beneficial to the body. Some bacteria help digest food, destroy disease-causing cells, or produce vitamins. Many of the microorganisms in probiotic products are the same as or similar to microorganisms that naturally live in our bodies.
What Types of Bacteria are in Probiotics?
Probiotics may contain a variety of microorganisms. The most common are bacteria that belong to groups called Lactobacillus and Bifidobacterium. Other bacteria may also be used as probiotics, and so may yeasts such as Saccharomyces boulardii. Different types of probiotics may have different effects. For example, if a specific kind of Lactobacillus helps prevent an illness, that doesn’t necessarily mean that another kind of Lactobacillus or any of the Bifidobacterium probiotics would do the same thing. Therefore, choosing the right type—or types—of probiotics is essential.
Understanding Gut Flora
The complex community of microorganisms in your gut is called the gut flora or microbiota. Within the gut there are hundreds of different types of microorganism—as many as 1,000, according to some estimations. This includes bacteria, yeasts and viruses—with bacteria making up the vast majority. Most of the gut flora is found in your colon, or large intestine, which is the last part of your digestive tract. Surprisingly, the metabolic activities of your gut flora resemble those of an organ. For this reason, some scientists refer to the gut flora as the “forgotten organ.”
A primal connection also exists between the gut and the brain via an extensive network of neurons, chemicals and hormones that constantly provide feedback about how hungry we are, whether or not we’re experiencing stress, or if we’ve ingested a disease-causing microbe. Gut bacteria both produce and respond to the same neurochemicals—such as GABA, serotonin, norepinephrine, dopamine, acetylcholine and melatonin—that the brain uses to regulate mood and cognition. Because of this gut-brain connection, the enteric nervous system (the part of the nervous system that is tasked with controlling the gastrointestinal system) has often been referred to as the “second brain.”
Your gut flora performs many functions that are important for health. Gut Flora manufacture vitamins, including vitamin K and some of the B vitamins. It also turns fibers into short chain fats like butyrate, propionate and acetate, which feed your gut wall and perform many metabolic functions. These fats also stimulate your immune system and strengthen your gut wall. This can help prevent unwanted substances from entering your body and provoking an immune response.
However, not all organisms in the gut are friendly. Your gut flora is highly sensitive to your diet, and studies show that an unbalanced gut flora is linked to numerous diseases—including obesity, type 2 diabetes, metabolic syndrome, heart disease, colorectal cancer, Alzheimer's and depression.
Probiotics—and prebiotic fibers (nondigestible food components that selectively stimulate the growth or activity of desirable microorganisms)—can help correct this balance, ensuring that your “second brain” is functioning optimally.
Probiotics and Digestive Health
Probiotics are widely researched for their effects on digestive health. When people take antibiotics, especially for long periods of time, they often experience diarrhea—even long after the infection has been eradicated. This is because the antibiotics kill many of the natural bacteria in your gut, which impacts gut balance and allows harmful bacteria to thrive. Probiotics also combat irritable bowel syndrome (IBS), a common digestive disorder, reducing gas, bloating constipation, diarrhea and other symptoms. Some studies also note benefits against inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis. Probiotics may also fight Helicobacter pylori infections, which are one of the main drivers of ulcers and stomach cancer.
The Impact of Probiotics on Weight Loss
People who are obese have different gut bacteria than those who are lean. Interestingly, animal studies indicate that fecal transplants from lean animals can make obese animals lose weight. Therefore, many scientists believe that your gut bacteria are important in determining body weight. In one study that involved 210 people with central obesity, which is characterized by excess belly fat, taking the probiotic Lactobacillus gasseri daily resulted in an 8.5% loss of belly fat over 12 weeks. When participants stopped taking the probiotic, they gained the belly fat back within four weeks. Evidence also suggests that Lactobacillus rhamnosus and Bifidobacterium lactis can assist with weight loss and obesity prevention—though this needs more research.
Other Health Benefits of Probiotics
There are many other benefits of probiotics. Probiotics reduce systemic inflammation, a leading driver of many diseases, They reduce symptoms of anxiety and depression in people with clinical depression, cause modest reductions in blood pressure, enhance immune function, possibly leading to a reduced risk of infections, including for the common cold, lower total and “bad” LDL cholesterol levels, and have also been shown to assist in the treatment of acne, rosacea and eczema, as well as other skin disorders.Others have reported that probiotics may improve heart health, immune function and symptoms of depression and anxiety.
Probiotics are helpful bacteria that can help to restore the optimal balance and health of your gut flora. However, maintaining a healthy gut is about more than just taking a probiotic supplement. Ultimately your daily diet, exercise, and lifestyle routines are the greatest factor in determining the health of your gut bacteria.