Hormones, Probiotics, and the Human Microbiome

Adapted from Probiotic Potential: Using “Friendly” Bacteria to Promote Healthy Digestion, Strengthen Immunity, and More
Connections publication of Women’s International Pharmacy

hormones probiotics and the human microbiomeThe microbiome organ is a collection of microbes or single-celled microorganisms—called microflora—that live on and in the body. The human body contains 100 trillion cells, and 90% of them are not even our own—nearly all of these are bacteria; the rest are yeasts and parasites. These microbes are incredibly diverse in size, shape, col­or and growth rates, and may include as many as 1,000 different species.

Among our body’s microbes you will find:

  • The “good” – Probiotics like Lactobacillus, a strain of bacteria commonly found in yogurts with active cultures.
  • The “bad” – Bacteria that usually result in serious illness, such as Salmonella.
  • The “risky” – Several bacterial species that are beneficial when they are in the right place and quantity, but may lead to health issues if their numbers are unbalanced or if they are located in the wrong part of the body. For example, species of Klebsiella make vitamins B12 and K when they’re in the small intestine, but may cause pneumonia when they’re inside the lungs.

The microbiome begins developing at birth and changes throughout our lifetime. Environment plays a larger role in determining microbiome makeup and health than genetics, which explains why members of the same household may have similar conditions even without being genetically related.

Microbial imbalance in our gut can affect other systems in our body, including our hormonal system. The digestive system plays an important role in the proper disposal of es­trogens from the body. When the flora in the intestines is disturbed, estrogen that should be excreted may instead be recycled into the bloodstream, creating hormone imbalance.

The development and changing of the microbiome over time may coincide with other physical changes. Many major life changes such as puberty, pregnancy, and menopause that affect the microbiome also affect hormone balance: University of Utah’s webpage Your Changing Microbiome provides just a few examples, saying: “puberty affects skin microbes by causing changes in skin oils. And pregnancy brings on changes in the vaginal microbiome: species start to grow that will colonize and benefit the baby as it’s born.”

Optimizing Microbiome Health to Maintain Hormone Balance

A probiotic—literally, “for life” in Greek—is defined as “a preparation or a product containing a sufficient number of live microorganisms to alter the flora of the host and bring about beneficial health effects.” In short, probiotics are “friendly” bacteria (and sometimes fungi) that we import into our system to hold more dangerous mi­crobes in check. A growing number of scientific studies have found that probiotics may aid both digestive and immune system health.

Yogurt, aged cheese, and many other cultured and fermented foods make up this category of “superfoods.” Probiotic foods or supplements are generally safe and widely available. Most people find them both tasty and easy to digest.

In general, probiotics promote healthy diges­tion. Microbes in the intestines make short-chain fatty acids (needed for GI tract health), antioxi­dants, amino acids, and vitamin K. Nutrients in fermented foods absorb more readily than nutrients in unfermented foods. Fer­mented foods use agents such as yeast, bacterium, molds, or enzymes to break down a substance into simpler substances; examples include converting milk to yogurt or cheese, fermenting soy to make miso, and fer­menting cabbage to make kimchi or sauerkraut.

Getting a beneficial effect for individ­ual health need depends on various factors, including:

  • The strain of probiotics selected and how the body can use it
  • The numbers of live probiotics in the pur­chased product, and whether they are stored and taken properly

Safety, Storage, and Use of Probiotics

Probiotics are safe for the majority of people, except for those at high risk for infections of all types (such as those with HIV/AIDS or cancer), or those taking immune-suppressive steroids. It is always advisable to check with your prac­titioner before taking any new supplements, as probiotics do have the potential to interact with some medications. Moreover, your practitioner can help you select the probiotic that is best suited to treating your particular condition, notes Dr. Kelly Dowhower Karpa in the book Bacteria for Breakfast: “You may have to search for the right probiotic, the appropriate number of microorganisms, or the necessary combination of probiotics until you find the right mix to successfully fill the bacterial niche missing in your gastrointestinal tract.”

Whether taken by pill (as a supplement) or by plate (in food), either form of probiotics can be effective as long as proper procedures of storage and ingestion are followed. Although it might seem that pill supplements would be required for the lactose-intolerant, that is not neces­sarily the case. Probiotics have been shown to help break down lactose, reducing symptoms of the illness and allowing sufferers to reintroduce dairy into their diet—at least in the form of yogurt and other fermented products.

Any form of probiotic should be purchased with care to ensure you are receiving the promised strain and quantity of live bacteria (or, in some cases, fungi), and that it has been properly stored. Foods containing live cultures must be kept refrigerated, and storage dates must be strictly followed. In Acidophilus and Your Health, author Frank Murray includes this advice when purchasing yogurts:

  • Always purchase yogurt with “live, active cultures,” including Lactobacillus acidophilus
  • Avoid frozen yogurt or pudding-style yogurts, which have stabilizing chemicals and artificial sweeteners added


Probiotics play an integral part in many of the body’s functions, including:

  • Microbiome health
  • Proper digestion
  • Hormone balance
  • Strengthening the immune system
  • Prevention of allergy development

When trying to incorporate dietary or supplemental probiotics into your lifestyle, recommendations from your healthcare practi­tioner may help guide you to reliable products from proven manufacturers. Finding the right probiotic for your individual needs may help optimize microbiome health—and, by extension, hormone balance and overall wellness.

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