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What are probiotics?

“According to the 2001 WHO/FAO definition, probiotics are ‘live microorganisms which, when administered in adequate amount, confer a health benefit on the host’. They are commonly consumed as part of fermented food, e.g. yogurt, or as dietary supplements.” 1 This same source explains that the term “gut flora” has been used in the past to describe the beneficial inhabitants of our gut, such as bacteria, but more correctly they are now referred to as “gut microbiota” or the microbiome—the community of microorganisms inhabiting the length and breadth of the mammalian gastrointestinal tract. 2 Significantly, while the average adult human body is made up of more than one hundred trillion cells, only tens of trillions contain human DNA. The rest are ‘guests’, part of the “human gut bacterial ecosystem”. A cautionary tale is that observations of humans after taking a course of broad-spectrum antibiotics (such as Cipro®) for a week or so, may result in reduction, and even elimination of beneficial bacteria and especially reduce microbiome species variety for at least 15 months. In turn, many reports have linked this decimation of competing bacteria with antibiotic-resistant “C. Diff” infections, that can last for months and can cause serious damage to the intestinal tissues. 3 The takeaway is this: our body, and especially our intestinal tract, is an ecosystem of (mostly) friendly organisms and what we do and do not do can help them or hurt them.

How can we improve probiotic health?

But wait, there's more to increasing beneficial bacteria in the gut than PRObiotics. Also important are PREbiotics, POSTbiotics and SYNbiotics. Here are some great definitions for these terms from a NIH published Clinical Review:4

  • Probiotics are supplements or foods that contain viable microorganisms that alter the microflora of the host
  • Prebiotics are supplements or foods that contain a nondigestible ingredient that selectively stimulates the growth and/or activity of indigenous bacteria
  • Postbiotics are non-viable bacterial products or metabolic byproducts from probiotic microorganisms that have biologic activity in the host
  • Synbiotics are products that contains both probiotics and prebiotics

For better probiotic health: Eat more soluble fiber foods (read plants) and eat probiotic fermented foods like kefir, kimchi, sauerkraut, etc. The presence of these types of foods will feed and benefit your existing bacterial colonies. Additionally, take a multi-species probiotic supplement from a reputable manufacturer.

Choosing a probiotic supplement

Dr Michael Murray N.D. suggests these guidelines for selecting probiotic supplements:

The quality of probiotic supplements depends on two main factors: (1) the characteristics of the strains contained in the supplement, and (2) adequate viability, so that sufficient numbers of bacteria are viable at the point of consumption. Viability at consumption depends on factors such as proper manufacturing and the “hardiness” of the strain, as well as packaging and storage of the product in the right amount of moisture and at the correct temperature (most need refrigeration.) Each species of bacteria comprises a multitude of strains. Some probiotic strains are resilient and strong, able to survive passage through the upper gastrointestinal tract and inhibit pathogenic bacteria, while others are weak and can’t survive or kill pathogenic bacteria. Better brands tell you details on the strain, usually indicated by an alphanumeric code. With probiotics, as with other supplements, be a smart consumer and read up on the top manufacturers. The dosage of probiotic supplements is based solely on the number of live organisms present in the product. Using products that list the number of live bacteria at expiration versus at time of manufacture is recommended. Successful results are most often attained by taking between 5 billion and 20 billion viable bacteria per day, measured in CFU (Colony Forming Units).5

1. Gut Microbiota for Health, see Probiotics

2. Defining the Human Microbiome, NIH Human Microbiome Project defines normal bacterial makeup of the body, Omics of the mammalian gut—New insights into function

3. The gut microbiome modulates colon tumorigenesis

4. Therapeutic use of prebiotics, probiotics, and postbiotics to prevent necrotizing enterocolitis: what is the current evidence?

5. Read Dr. Murray's article: Everything You Always Wanted to Know About Probiotics

How We Choose Our Top 5 Supplements (View our Site Disclaimer)

We recommend any of the five products listed below equally and so present our choices in alphabetical order by brand. We do not receive any compensation in exchange for our recommendations. Read more about how we make our selections.

Garden of Life Dr. Formulated Once Daily Probiotic

Garden of Life® Dr. Formulated Probiotics

Here is a whole line of probiotics formulated by Dr. Perlmutter, M.D., author of the best-selling book "Brain Maker: The Power of Gut Microbes to Heal and Protect Your Brain for Life"


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This line of probiotics has a lot going for it:

  • • high-potency based on "At Expiration Date under recommended storage conditions"
  • • multi-strains with both upper and lower bowel families
  • • made from diverse strains that are resistant to stomach acid and bile
  • • includes organic plant fiber prebiotics in each capsule

This line is formulated by a medical doctor and researcher and do NOT require refrigeration. The downside is that they leave out many well documented strains that have been thoroughly tested for hardiness and beneficial effects, but do require refrigeration.

Example ingredients: Men's Daily Probiotic Blend each capsule:

  • • Lactobacillus acidophilus
  • • Lactobacillus casei
  • • Lactobacillus gasseri
  • • Lactobacillus plantarum
  • • Lactobacillus paracasei
  • • Lactobacillus brevis
  • • Lactobacillus bulgaricus
  • • Lactobacillus rhamnosus
  • • Lactobacillus salivarius
  • • Lactobacillus fermentum
  • Total Lacto Cultures (35 Billion CFU)

  • • Bifidobacterium lactis
  • • Bifidobacterium bifidum
  • • Bifidobacterium breve
  • • Bifidobacterium infantis
  • • Bifidobacterium longum
  • Total Bifido Cultures (15 Billion CFU)

  • Total Probiotic Cultures 50 Billion CFU¹
  • Organic Prebiotic Fiber Blend 365mg:
  • Organic Potato [Resistant Starch] (tuber), Organic Acacia Fiber (A. senegal)

Natural Factors Ultimate Probiotic

Natural Factors® Ultimate Probiotic Line

A whole line of various potencies guaranteed until expiration date. Requires refrigeration.


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These formulas have explicit strain identifications and stated details such as derivation and content per servings. With regard to stomach acid resistance, not all strains are created equal. Natural Factors has carefully selected naturally acid-resistant strains so that they may be consumed at any time, with or without meals, and are safely delivered to the intestine unharmed.

Other ingredients: Vegetarian capsule (carbohydrate gum [cellulose], purified water), potato starch, magnesium stearate (vegetable grade), ascorbic acid. Contains milk and soy. Contains no artificial colors, preservatives, or sweeteners; no sugar, wheat, gluten, yeast, corn, egg, fish, shellfish, salt, tree nuts, or GMOs

Example for Natural Factors Ultimate Probiotic Critical Care 100 Billion:

  • Proprietary Synergistic Blend:
  • Total Active Cell Count 100 billion CFU (CFU: colony forming units)
  • • Lactobacillus plantarum (HA-119)(whole cell)(plant) 38 billion CFU
  • • Lactobacillus paracasei (HA-196)(whole cell)(dairy) 23 billion CFU
  • • Bifidobacterium breve (HA-129)(whole cell)(dairy) 15.25 billion CFU
  • • Lactobacillus acidophilus (HA-122)(whole cell)(human) 10 billion CFU
  • • Bifidobacterium longum (HA-135)(whole cell)(human) 10 billion CFU
  • • Lactobacillus rhamnosus (HA-111)(whole cell)(human) 2 billion CFU
  • • Bifidobacterium lactis (HA-194)(whole cell)(dairy) 1 billion CFU
  • • Bifidobacterium bifidum (HA-132)(whole cell)(human) 0.5 billion CFU
  • • Bifidobacterium infantis (HA-116)(whole cell)(human) 0.25 billion CFU

Nature's Way Primadophilus Reuteri

Nature's Way® Primadophilus® Reuteri, Superior Probiotic

Supports intestinal health and features Lactobacillus Reuteri, a probiotic strain that has been shown to colonize the intestines to help maintain digestive balance and support immune health.


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Probiotic Blend providing 3 Billion CFU with guaranteed potency of at least 3 billion CFU at expiration date: (Lactobacillus reuteri UALre-16), L. acidophilus (DDS-1), Bifidobacterium longum (Bl-05), L. rhamnosus (HN001) plus Prebiotic Support with NutraFlora® scFOS® (short-chain fructooligosaccharides) optimal food source of intestinal microflora. There is published research on each of these probiotic strains known by their individual strain codes.

Natures Way Primadophilus Kids

Nature's Way® Primadophilus® Kids

Primadophilus® Kids probiotic chewable features 3 probiotic strains specifically designed for kids, with kid-friendly cherry and orange flavors.


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Designed specifically with children age 2-12 in mind, sweetened with Xylitol. Good reviews on taste. Other ingredients: inulin, hydroxypropyl cellulose, stearic acid, natural flavor, citric acid, magnesium stearate, silica.

  • Proprietary Probiotic Blend providing 3 Billion CFU
  • • Lactobacillus acidophilus (La-14®)
  • • Lactobacillus plantarum (Lp-115®)
  • • Bifidobacterium bifidum/lactis (Bb-02)

NOW Probiotic 10, 100 Billion 10 Probiotic Strains

NOW® Probiotic 10

Includes 10 Probiotic strains, with verified identity and various potencies for upper and lower bowel support.


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Probiotic-10 utilizes bacterial strains that have been clinically validated for their support of healthy immune system function. Probiotic strains in this product have been identity-verified using DNA-fingerprinting technology.

  • Blend of 10 Strains of Probiotic Bacteria (25 Billion CFU potency guaranteed until “best by” date):
  • • Lactobacillus acidophilus (La-14)
  • • Bifidobacterium lactis (BI-04)
  • • Lactobacillus plantarum (Lp-115)
  • • Lactobacillus casei (Lc-11)
  • • Lactobacillus rhamnosus (Lr 32)
  • • Lactobacillus paracasei (Lpc-37)
  • • Bifidobacterium breve (Bb-03)
  • • Streptococcus thermophilus (St-21)
  • • Lactobacillus salivarius (Ls-33)
  • • Bifidobacterium longum (BI-05)

How We Choose Our Top 5 Supplements

Ingredients with measurable efficacy: Some supplement ingredients have had decades of scientific study and thousands of published studies describing their measurable efficacy and benefits to human nutrition. But some are only recently showing up on the market and have little science to explain their properties. Since you can't buy or try everything, we recommend products with studied ingredients.

Added value/complementary nutrients: Much of the cost of supplements is in their packaging, so if a product contains several complementary ingredients for its intended benefit, then we usually recommend that product over a single ingredient product. The exception is a single ingredient product that has special recognition as superior to similar but less effective products.

Different forms (tablets, powders, etc.): Some people just hate to take pills of any kind. So, when there’s a chewable, liquid, powder or gummy option that’s effective, we may also recommend those products.

Good manufacturing practices and reputation: There has been an explosion of supplement brands in the last 10 years. Many of these brands live only online and have ownership outside of USA regulations or ownership whose identity is sometimes hard to determine. We recommend companies that have made and marketed supplements for many decades in the USA and have earned good reputations for closely following FDA, GMP, and FTC guidelines, submitting to protocols that verify purity and potency and refraining from misleading product claims.

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