The human body houses as many as 100 trillion bacteria. If those were dollars, that would be almost five times the national debt.
They're all part of the microbiome: the collection of human cells and other living microbes, including bacteria, that live in and on the human body. Though the estimated ratio of human cells to bacterial cells is in debate (estimates range from one-to-one to one-to-10), we know that a balance between "good" bacteria (probiotics) and "bad" bacteria is essential for human health.
"The levels of bacteria in the body are constantly changing," says Julie Fortenberry, a dietitian at Touro Infirmary. "If you knew how important a role bacteria play in health — 70 percent of the body's immunity is in the gut — if the body isn't absorbing nutrients, [immunity suffers]. You have to heal the gut and make it whole again."
Gut bacteria play a role in several body functions, including digestion, nutrient absorption, metabolism and immunity. The American Academy of Microbiology's Human Microbiome Project is working to establish the baseline of the normal microbiome. Scientists and researchers consider this aggregate of bacteria and other microbes an organ that works with the endocrine and nervous systems. Like other organs, the microbiome needs care in order to work properly.
Doctors increasingly are recommending probiotics to people suffering from gastrointestinal (GI) disorders and diseases, sometimes in conjunction with medications. Probiotics reintroduce the live strains of good bacteria that are organically found in the intestines. They repair the gut by restoring bacteria that might have been eradicated by improper diet or antibiotics, which kill all bacteria indiscriminately. Probiotics are available as supplements and occur naturally in fermented foods.
"[Generally,] the more natural the source, the better," Fortenberry says. "I would love to recommend food sources, but the most common [are] yogurt ... [or] kefir, which often contain a lot of sugar. You can't absorb the probiotic because of all the sugar. Sauerkraut is fermented, so it has lots of probiotics, as [does] kombucha. But you have to look out for those harmful ingredients. Pasteurization kills off many of the probiotics."
When it comes to probiotics, supplements are not more or less effective than foods like dairy products or kimchi. When choosing the food route, consumers need know about ingredients like sugar, salt and fat, and whether a food is processed. These can affect whether probiotics can survive.
A study conducted by the European Society for Primary Care Gastroenterology (ESPCG) found most healthy adults' systems benefit from probiotic therapy. Very few test subjects experience adverse reactions to probiotics. The ESPCG conducted 28 studies on the effect of probiotics on patients with a range of lower GI symptoms, and only two patients discontinued the clinical trial because of adverse reactions. Those reactions occurred with equal frequency in the study's control group, which consisted of participants not undergoing probiotic treatment.
Fortenberry's professional experience reflects those outcomes. In 12 years, she has seen only one client whose body rejected the supplements.
"Sometimes you have so much bad bacteria present, taking good bacteria can make you sicker," she says. "That's a rare case. If you notice that the probiotics don't agree with you, discontinue use and consult a doctor."
People whose immune systems are com- promised (for example, people who are undergoing chemotherapy) should consult a doctor before taking probiotics.
Because probiotics are a dietary supplement and not a medication, the FDA does not regulate their production or manufacturers' health claims. Instead, third-party evaluators like Consumer Lab have stepped in. Fortenberry approves of independently assessed products and offers more advice on selecting probiotics.
"[The product] should contain different strains [of bacteria], and the label should denote the number of active strains," she says. "Probiotics must reach the large intestine to be absorbed. Otherwise, stomach acid may break down the probiotic before it gets where it needs to go. Don't get ones that digest quickly."
Fortenberry says reducing the intake of sugars and processed food, managing stress and decreasing the frequency of antibiotic treatments benefits gut bacteria. Eating a diet rich in fiber, fruits and vegetables contributes to overall health.
The International Scientific Association for Probiotics and Prebiotics (ISAPP) suggests consumers check product labels for shelf lives, to make sure the bacteria strains are still viable. Manufacturers usually denote the initial number of live strains, but offer no guarantees that those strains will still be active by the time of purchase or consumption. On its website, the ISAPP offers interactive resource guides that allow consumers to enter their gender and GI symptoms and select the appropriate probiotic from recommended brands.
Another probiotic plus: Data indicates that probiotics benefit more than just GI issues. A study published in the Journal of Neurogastroenterology and Motility demonstrates that certain strains of probiotics can treat central nervous system disorders like anxiety, depression and autism. The human microbiome still holds its mysteries, but individuals have the ability to influence their unique bacterial makeups.