Probiotics: Not All Bacteria Are Created Equal


Bacteria. The word alone has many of us reaching for the nearest bottle of Purell (particularly at this time of year), forget about trying to purposefully ingest these invisible microorganisms. Yet, in the past few years, we have been inundated with promises of products and supplements that contain “live active cultures” to “promote immunity,” “maintain digestive health” and “support weight loss.” What are these “cultures” and do they do what they say they do?

First, a quick review of terms:

Probiotics: These are the “good” bacteria that largely inhabit our gut. They are live microorganisms that carry out a multitude of functions including: protecting us from infection, digesting the fiber from the foods we consume, synthesizing vitamins (B12 and K) and releasing beneficial substances in certain foods (such as the cancer-protective isothiocyanates found in broccoli, cauliflower etc). There are many different strains of probiotic bacteria and recent research has found that different strains have different therapeutic effects.
Natural sources include: yogurt, cottage cheese, some fermented soft cheeses (e.g. Gouda), buttermilk, kefir, soy sauce, tempeh, miso, sourdough bread, kimchi and fresh sauerkraut. (Note: pasteurization kills probiotics)

Prebiotics: These are the non-digestible parts of certain plant-based foods that probiotic bacteria feed off of. In order for the probiotics in your digestive tract to flourish, you need to feed them, which is why it is recommended that you include both in your diet.

Natural sources include: wheat, barley, rye, flax, oatmeal, beans/lentils, onions, garlic, leeks, asparagus, leafy greens, berries, bananas and honey.
(For a more comprehensive background review on Probiotics, check out this 2009 City Girl Bites post by Marisa Beck, MS, RD:

Ok, so the prebiotics seem pretty straight-forward, right? Eat lots of fruits, veggies and whole grains and you’re pretty much covered in terms of providing a food source for the “good bacteria” that live in your intestines (as well as providing your body with needed vitamins, minerals, antioxidants etc). But what about these good bacteria–do you have enough of them in your gut already? If not, which strains do you need and what products can they be found in?

Do you have enough already?
This is difficult to assess for a number of reasons: there is not yet a diagnostic test to determine how many probiotic bacteria you have living in your digestive tract and even if there was, this area of research is at such an early stage, there are no “normal” ranges that have been set as standard in the medical community. However, some clues that your gut’s microflora may be out of balance include: chronic abnormal GI symptoms (diarrhea, constipation, bloating, excess gas) that your doctor has concluded are not the result of a specific medical condition/infection; frequent vaginal yeast infections; and frequent/increased susceptibility to minor infections caused by viruses and (“bad”) bacteria. If you have any of these symptoms (despite your doctor giving you a clean bill of health) it’s possible your gut’s microflora is to blame and it may be worth experimenting with some pre and probiotic diet additions.

Which probiotic strains are best for you?
Well that depends on whether you have a specific health complaint and what that complaint is.
Use the chart below to help you identify which probiotic strains have been associated with helping specific health conditions:


As mentioned earlier, research on probiotics is very much in its preliminary stages. The conditions referenced above are the only ones to-date that studies have consistently demonstrated benefits for (and even for these, the research is not definitive). There is as yet no solid evidence indicating that probiotics can assist with weight loss, energy level, heart disease or any other medical conditions.

So now you have a sense of which strains you should be on the lookout for, where can you find them? See the “Product Guide” below for some examples:

Product Guide

Chobani Fat-Free Plain Yogurt
-Contains S Thermophilus, L Bulgaricus, L Acidophilus, Bifidus and L Casei
-May help with antibiotic-associated diarrhea, lactose indigestion, vaginal yeast infections and weakened immunity

Brown Cow Vanilla Yogurt
-Contains S Thermophilus, L Bulgaricus, L Acidophilus, Bifidus
-May help with antibiotic-associated diarrhea, lactose indigestion, vaginal yeast infections and weakened immunity

Dannon Activia
-Contains L Bulgaricus, S Thermophilus and Bifidobacterium lactis DN-173 010
-May help with constipation

Lifeway Organic Whole Milk Kefir (Plain)
-Contains L Reuteri, Bifidobacterium lactis, L Casei, L Lactis, L Acidophilus, L Plantarum, L rhamnosus, B bacterium longum, Leuconostoc cremoris, B Bacterium Breve, S Diacetylactis and S Florentinus.
-May help with constipation, weakened immunity, antibiotic-associated diarrhea and irritable bowel syndrome

Nancy’s Organic Low-Fat Cottage Cheese
-Contains L Acidophilus and B Bifidum
-May help with antibiotic-associated diarrhea and weakened immunity

Fresh (unpasteurized) Sauerkraut
-Contains L Acidophilus
– May help with antibiotic-associated diarrhea and weakened immunity

Remember, as with nutrients, it is always preferable to get your pre and probiotics from food (supplements are not required to undergo FDA approval and are also not as well absorbed by the body as whole foods). However, if you do decide to purchase a supplement, stick to one of the brands listed below (which have been well-studied and appear to be safe and properly labeled) or be sure to check the strain against the chart above to see if there is in fact research supporting its use for the health claims listed on the label. Also remember to always check with your health care provider before taking any supplements.

Supplement Guide

-Contains S. Boulardii lyo (a yeast-based probiotic)
– May help with antibiotic-associated diarrhea

– Contains L rhamnosus GG
– May help with antibiotic-associated diarrhea and Irritable Bowel Syndrome


-Contains Bifidobacterium infantis 35624
-May help with Irritable Bowel Syndrome

-Contains L rhamnosus GR-1 and L Reuteri RC-14
-May help treat vaginal infections in combination with antibiotic therapy

I’d like to thank Shabnam Greenfield, MS, RD for writing this article. Shabnam Greenfield is a New York City-based Registered Dietitian. She counsels individuals with a range of health and wellness concerns privately, and also works with people living with HIV/AIDS at a Harlem-based non-profit. She received her M.S. in Nutrition from Teachers College, Columbia University.
Follow her on Twitter @RDShabnam and on Facebook: RD Shabnam.

Reddy, S. Probiotics’ Benefit May Be More Than a Gut Feeling. Wall Street Journal, Nov 26 2012.
Schardt, D. Living in a Microbial World. Nutrition Action. July/August 2012.
Schardt, D. Probitoics: “Good: Bacteria to the Rescue? Nutrition Action. April 2010.
Zanteson, L. Gut Health and Immunity. Today’s Dietitian, Vol 14, No 6, p 58.



I especially love problem-solving, whether it’s helping women defeat issues plaguing them for years, helping a busy executive find practical ways to get heart healthy, or providing tips to help you reverse diabetes. That’s why I’m on a constant quest to expand my knowledge by staying on top of the latest research.

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