Trillions of microorganisms collectively make up the human microbiome. One of the first to colonize the human gastrointestinal tract is Bifidobacterium, a widely researched bacteria for its many health benefits. This article will discuss the symbiotic relationship between humans and Bifidobacterium spp., why it is crucial to maintain healthy levels of this good bug, and how to do so.

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What Is Bifidobacterium spp.?

Bifidobacteria are commensal bacteria of the human microbiome belonging to the Actinobacteria phylum. Bifidobacteria are Gram-positive, anaerobic, non-motile, and non-spore-forming polymorphic rod-shaped bacteria. (1)

Bifidobacteria are one of the first resident colonizers of the infant's gut, representing over 70% of the total intestinal microbiome of a breastfeeding infant. Studies have linked bifidobacterial colonization to vertical transmission (from mother to child); the mother's vaginal tract, gastrointestinal tract, breast milk, placenta, and amniotic fluid are all sources of Bifidobacterium. With age, the composition of the intestinal microbiome changes, and Bifidobacteria constitute a smaller percentage of the total microbiome, with research estimating a 2-14% relative abundance. (1, 2)

What Are the Main Bifidobacterium Bacteria?

There are at least 80 species of bacteria belonging to the Bifidobacterium genus. Bifidobacteria can generally be categorized based on where they are naturally encountered - either in the human gastrointestinal tract (HRB) or the environment and other animals (non-HRB). The predominant HRB species in the infant gastrointestinal tract include B. breve, B. longum subsp. infantis, B. longum subsp. longum, and B. bifidum, whereas the dominant species of the adult intestines are B. adolescentis, B. catenulatum, B. pseudocatenulatum, and B. longum subsp. longum. (1)

What Are the Health Benefits of Bifidobacterium spp.?

Bifidobacterium spp. digest fiber and other complex carbohydrates that the human body can't digest on its own in a process called fermentation. Fermentation results in the production of short-chain fatty acids (SCFAs), which are known to provide numerous health effects, ranging from supporting a healthy digestive tract to promoting normal immune function (3). Bifidobacteria are also responsible for synthesizing B vitamins, fatty acids, and neurotransmitters. The production of these nutrients and chemicals is responsible for the health benefits attributed to Bifidobacterium spp. Conversely, a lack of diversity within the intestinal microbiome, and insufficient levels of beneficial bacteria, including Bifidobacterium, results in an elevated risk of intestinal infections, increased intestinal permeability ("leaky gut"), decreased intestinal immune factors, and high levels of inflammation. The lack of Bifidobacterium spp. is correlated with many diseases, outlined below.

Digestive Health

People with celiac disease, irritable bowel syndrome (IBS), and H. pylori-related gastric ulcers and cancer have been found to have lower levels of Bifidobacterium compared to healthy controls. What's more, probiotic supplementation with Bifidobacterium spp. improves IBS digestive symptoms, prevents colorectal cancer, and reduces intestinal inflammation in patients with inflammatory bowel disease (IBD) (4).

Immune System

Bifidobacterium is a contributing player in the maturation of the immune system in infants and the regulation of immune function through life due to its interactions with human immune cells and modulation of innate and adaptive immune processes.

Bifidobacteria can prevent gastrointestinal infections by competing with pathogenic organisms for binding sites on intestinal epithelial cells and producing acetate, a SCFA that helps prevent bacterial toxins from crossing into systemic circulation. (4, 5)

Compared to healthy controls, lower levels of B. longum are noted in children with allergic asthma and dermatitis. The supplementation of B. lactis for three months reduces food allergy by increasing the Treg and Th17 immune cells ratio. Similarly, patients with allergic rhinitis experience reduced allergy recurrence and symptom severity when supplemented with Bifidobacterium-containing oral probiotics.

Metabolic Syndrome

Metabolic syndrome is a constellation of increased blood pressure, blood sugar, central body fat, and serum cholesterol. Lower levels of Bifidobacteria have been measured in obese patients, and its presence in the gut likely influences metabolism and the correction of metabolic dysfunction.

Dietary fiber intake has been shown to reduce body weight and the risk of diabetes. Although the underlying mechanisms are not entirely understood, the enhancement of insulin sensitivity and the beneficial alterations in the gut microbiota are thought to contribute to the beneficial effects of fiber. SCFAs produced by Bifidobacterium spp. (and other beneficial gut microbes) normalize blood glucose by influencing satiety hormone production and reducing total cholesterol. (6, 7)

Mental & Neurological Health

Researchers have found that children with autism have lower levels of Bifidobacteria in the gut, which could exacerbate leaky gut and contribute to a leaky blood-brain barrier. Gastrointestinal symptoms and quality of life in patients with autism have improved when adding Bifidobacterium into the diet. (8)

Studies have also shown beneficial effects in the treatment of depression. Bifidobacteria supplementation has been associated with lower depression scores, negative thoughts, and psychological distress. (9-11)

What Causes Low Levels of Bifidobacterium spp.?

As discussed above, aging does correlate with a natural decline in Bifidobacterium numbers within the gut microbiome. Other factors, however, can escalate this decline, causing an insufficiency-type of dysbiosis.

Diet is a critical factor required to support Bifidobacterium prosperity, and a diet lacking in fiber and fermentable carbohydrates is associated with lower Bifidobacterium spp. Research has correlated a high beef (animal protein) diet with decreased B. adolescentis and a low FODMAP diet with decreased B. adolescentis and B. longum. A small study also noted reduced Bifidobacterium spp. after one month of a gluten-free diet.

Bifidobacterium has been measured at lower levels after significant weight loss induced by bariatric surgery.

Cigarette smoking is also associated with decreased Bifidobacterium levels.

What Causes High Levels of Bifidobacterium spp.?

Higher levels of Bifidobacterium spp. are typically related to diet and physical activity. Dietary intake of whey and pea proteins, guar gum, walnuts, prebiotics, fermented foods, and polyphenols have all been shown to increase beneficial Bifidobacterium. (12-14)

Prebiotic supplements and Bifidobacterium-containing probiotics can also cause high levels of Bifidobacterium spp. if taken at high doses and/or for long periods. (12)

One study found that women physically active for at least three hours weekly had higher fecal Bifidobacterium spp. than women who were not; the study also noted key dietary differences (i.e., increased fiber, fruit, and vegetable intake) in the physically active group, which likely plays into this difference. (15)

How to Test Bifidobacterium spp.

Comprehensive stool tests are the best tool for an in-depth analysis of the intestinal microbiome and quantification of the growth of Bifidobacterium spp. within it. The GI-MAP by Diagnostic Solutions, GI Effects by Genova Diagnostics, and GI360 by Doctor's Data are all popular test options that measure the growth of Bifidobacterium spp. in the patient-provided stool sample(s). The GI Effects® Comprehensive Profile by Genova Diagnostics may be a preferred test for those wanting a more specific analysis of specific species within the Bifidobacterium genus; this test not only provides a growth measurement for Bifidobacterium spp., but also for B. adolescentis, B. animalis, B. bifidum, B. breve, B. catenulatum, B. dentium, B. infantis, B. lactis, and B. longum.

Foods That Help Increase Bifidobacterium spp. Levels

Mediterranean-style dietary patterns boost beneficial Bifidobacterium levels in the gut microbiome. The Mediterranean diet is highly regarded as healthy and well-backed by research to promote health in many different capacities. Emphasizing mainly plant-based foods, it is distinguished by a high intake of beneficial fatty acids, polyphenols, antioxidants, fiber, and vegetables. High-to-moderate intake of olive oil, fruits, vegetables, legumes, whole grains, nuts and seeds, and fish are responsible for this diet's ability to reduce intestinal inflammation and cultivate the growth of beneficial flora. (12)

Supplements That Increase Bifidobacterium spp. Levels

Supplements may be required in addition to dietary changes to modify the microbial composition within the human microbiome quickly.

Probiotics are live microorganisms that confer health benefits to the host when consumed. Probiotic supplements most commonly contain various species and strains of Lactobacillus and Bifidobacterium. Bifidobacterium-containing oral probiotics are effective in increasing the number of fecal Bifidobacterium.

Prebiotics, non-digestive dietary components that stimulate the growth of probiotic microorganisms, have also been shown to have a beneficial impact on the microbiome by increasing levels of Bifidobacterium. Prebiotics can be found in foods like soybeans and whole grains but are also commonly available in dietary supplements such as fructooligosaccharides (FOS), galactooligosaccharides (GOS), and inulin. (4, 12)

How to Make Sure You Are Getting High-Quality Bifidobacterium spp. Supplements

You'll want to research and/or talk to a medical professional when deciding which probiotic will most effectively treat your dysbiosis. Choosing a medical-grade probiotic ensures it is manufactured following FDA regulations and tested by a third party for quality.

Consider colony-forming units (CFU), bacterial strains, and storage instructions when reading a probiotic nutritional label. Probiotic efficacy is dependent on probiotic strain and dosage. A probiotic label should list the probiotic strains included; choose one with researched strains specific to your health concern. The CFU tells you the number of bacteria administered per each probiotic dose. Over time, CFU will decline, making probiotics less effective. Ensure you are taking a probiotic that hasn't expired, sufficiently dosing the probiotic, and storing your probiotic correctly (typically by refrigeration). (16)

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Summary

Bifidobacterium is a genus of bacteria consisting of many beneficial bacterial species. These bacteria are essential for human health, shown to prevent and treat many different health conditions and diseases. Eating a healthy diet with a wide variety of high-fiber, prebiotic, and probiotic foods is one of the best ways to increase and maintain healthy levels of Bifidobacterium in the gut. As needed, high-quality Bifidobacterium probiotics can be used to treat different health conditions. Talk to your functional health provider about whether microbiome testing and probiotic supplementation are indicated for you.