Grow Youthful: How to Slow Your Aging and Enjoy Extraordinary Health
Grow Youthful: How to Slow Your Aging and Enjoy Extraordinary Health


Bacteria in your body

The result of taking antibiotics

Probiotics protect against the damage done by antibiotics - study

Helicobacter pylori - our dominant microbe now near-extinct

Sources of good probiotic bacteria

New generation probiotics made with specially selected bacteria

List of good probiotic bacteria and yeasts


Bacteria in your body

Up to 2.5% of your body's weight consists of bacteria. Bacteria have lived in and on all animals since life evolved. About 1000 different strains of bacteria, yeasts, protozoa and other microorganisms weighing over 2 kg live in your body (7). Most of them are in your digestive tract, but they are also in your nose, throat, ears, eyes, skin, genitals, urethra and throughout your body. It is essential to have good bacteria on your throat, urethra, nasal passages, vaginal walls etc. (9) They play an critical part in your immune system, and protect you from invading pathogenic bacteria, fungi and viruses. Bacteria are resident on all your membranes, protecting you against infection. Bacteria play an essential role in your digestion - without them, you cannot break down many foods and absorb the nutrients. Having the right bacteria in your gut helps organs all over your body function correctly, including your brain. Studies (11, 12, 13) confirm the protective effects of probiotic bacteria against depression and other brain maladies. Bacteria assist in the production of some vitamins (B12, K, etc). The bacteria, fungi, protozoa and other microflora making up your microbiome are essential for life and good health, and a healthy balance (symbiosis) is built up over your lifetime (7).

Skin probiotic

probiotics for the skin

Restore good bacteria
to your skin

Babies get their founding bacterial population from their mothers while passing through the vagina at birth. Babies born by caesarean section miss out on this important dose of bacteria. Mothers milk from breast feeding contains a wide variety of bacteria that the infant will not get when fed pasteurised formula milk. Breast feeding builds up a wide range of healthy gut bacteria in the infant. Research (10) shows that breast fed infants have a significantly different intestinal microbial biome from those which are bottle fed, and that these bacteria lock in a strengthened immune system for their whole life. (10)

In the first few years of their life, infants add to this bacterial population by crawling around and putting all sorts of things in their mouths. The presence of animals (pets or farm animals) and siblings is also important. This is a once-only opportunity to build up these bacteria, before the stomach acid gets too strong and the immune system becomes a powerful bacterial barrier. New research (8) confirms that dirty kids are healthy kids.

The result of taking antibiotics

By the time the average child in the USA and other developed countries is 18 years old, he or she has received 10-20 courses of antibiotics (1). In a few cases, the use of these antibiotics has been life-saving or has stopped a serious infection. However, the assumption that antibiotics are generally safe has:

When you take an antibiotic, you indiscriminately destroy most of the friendly microflora in your body in addition to the target bacteria. There is evidence that the friendly flora that take a lifetime to build up never fully recover. After taking an antibiotic, you are vulnerable to invasion by bacteria, fungi and viruses.

Here are some of the problems that can arise from bacterial imbalance. The level of these diseases have more than doubled in many populations in line with the increased use of antibiotics (2). This list is not complete - I suspect that many more degenerative diseases have a lack of beneficial bacteria, or a bacteria imbalance as their root cause.

Probiotics protect against the damage done by antibiotics - study

A ground-breaking study (14) published in 2017 showed that a standard course of antibiotics given to pregnant mice and young pups permanently altered their brains and their behaviour. The young mice were aggressive and less sociable. There were permanent changes to their brain chemistry, brain structure and disruption of the blood brain barrier, with inflammation in the brain. The study also noted the strong association between antibiotics and irritable bowel syndrome (IBS), obesity, and a wide range of psychiatric disorders.

The good news shown by this study was that most of this damage did not occur in a group of mice that were fed probiotics during the antibiotic course!

Helicobacter pylori - our dominant microbe now near-extinct

A century ago, Helicobacter pylori was the dominant microbe in the stomachs of almost all people (it is one of few bacteria that can actually live in the acidity of the stomach). By the year 2000, fewer than 6% of children in the USA, Sweden and Germany were carrying it. This is almost certainly because of antibiotics - for example, a single course of amoxicillin or a macrolide (used to treat ear infections in children) eradicates H. pylori in up to half of all cases.

H. pylori is associated with gastritis, gastric ulcers, duodenal ulcers and stomach cancer. However, most people who harbour this bacterium have no symptoms. It is more likely that such problems have developed because of a bacterial imbalance allowing the H. pylori to get out of control.

Having some of the benign strains of H. pylori in your stomach and colon is likely to be highly beneficial (7). Several significant benefits have already been identified from having H. pylori in your stomach. It affects the regulation of two hormones, ghrelin and leptin produced in the stomach and involved in hunger, sateity (feeling full) and energy balance. With the disappearance of H. pylori from most people's digestive tracts, there has been an increase in gastroesophageal reflux and related diseases such as Barrett's oesophagus and oesophageal cancer.

Several large studies have found that people without H. pylori are more likely to develop asthma, hay fever, and skin allergies in childhood (4,7). Another study showed that infecting the stomachs of mice with H. pylori protected them against asthma (5). Bacterial imbalance may cause the overproduction of fat cells, in preference to the production of muscle and bone cells.

Eventually, some sub-species of H. pylori will be made available as a probiotic supplement. But right now, there is only one way that I can think of, that you can get a dose of this essential but much maligned bacteria: by means of a fecal transplant.

Bacteroides fragilis is another example of a beneficial bacteria that is being wiped out. B. fragilis moderates the immune system and prevents excessive inflammation. The absence of this bacteria is likely responsible for a significant increase in many autoimmune disorders such as Crohn's disease, type I diabetes and multiple sclerosis.

Sources of good probiotic bacteria

My recipe book The Grow Youthful Recipe Book includes the recipes for many live-bacteria probiotic foods. It includes several live-culture foods and drinks, and lots practical advice.

A new-generation probiotic that combines 29 species of soil-based beneficial microflora with a humic/fulvic acid prebiotic that enhances SBO proliferation.

Australian distributor

USA distributor

NOTE: Store-bought cultured foods are usually pasteurised, which means that all the living bacteria they used to contain have been killed. If you buy any cultured food, it is essential that it is alive. This is why it is much better to make these foods yourself, or buy them direct from someone who has made them with integrity.

List of good probiotic bacteria and yeasts

This list of bacteria and yeasts is only a short example of what can be found in living foods, as opposed to the strictly-bred bacteria in probiotic supplements. Bacteria are not like other living organisms that breed true according to the genetic program that is passed down through successive generations. Instead, bacteria are actually able to morph from one species to another, horizontally transferring their genes through a variety of wonderful biological mechanisms. This means that the this list of bacterial species is just a starting point. The microorganisms can morph and change in response to the environment in which they are living. It is quite possible for one species of Lactobacillus to morph into another, and I would assume it is also possible for Lactobacillus to morph into other bacilli. With bacteria it is more or less that case that whatever the environment dictates will spontaneously appear. So whilst probiotics provide a starting point to regaining good health, the condition of your body,(particularly) the food you eat, and the environment that you live in will also have a large affect.


1. Sharland, M. J. Antimicrob. Chemoth. 60 (suppl. 1), i15-i26 (2007).

2. Martin Blaser. Antibiotic overuse: Stop the killing of beneficial bacteria. Nature, 24 August 2011. 476,393-394.

3. Blaser, M. J. & Falkow, S. Nature Rev. Microbiol. 7, 887-894 (2009).

4. Chen. Y. & Blaser, M. J. Arch. Intern. Med. 167, 821-827 (2007).

5. Arnold, I. C. et al. J. Clin. Invest. 121, 3088-3093 (2011).

6. Dominguez-Bello, M. G. et al. Proc. Natl Acad. Sci. USA 107, 11971-11975 (2010).

7. Blaser, Martin J. Who are we? Indigenous microbes and the ecology of human diseases EMBO reports 7 (10): 956-60. doi:10.1038/sj.embor.7400812. PMC 1618379. PMID 17016449.

8. Torsten Olszak, Dingding An, Sebastian Zeissig, Miguel Pinilla Vera, Julia Richter, Andre Franke, Jonathan N. Glickman, Reiner Siebert, Rebecca M. Baron, Dennis L. Kasper, and Richard S. Blumberg. Microbial Exposure During Early Life Has Persistent Effects on Natural Killer T Cell Function. Science Published online 22 March 2012; DOI:10.1126/science.1219328

9. Shruti Naik, et al. Compartmentalized Control of Skin Immunity by Resident Commensals. Published Online July 26 2012, Science DOI: 10.1126/science.1225152

10. Dennis J. Hartigan-O'Connor, Amir Ardeshir, Nicole R. Narayan, Gema Mendez-Lagares, Ding Lu, Marcus Rauch, Yong Huang, Koen K. A. Van Rompay, Susan V. Lynch. Breast-fed and bottle-fed infant rhesus macaques develop distinct gut microbiotas and immune systems. Science Translational Medicine, 3 September 2014: Vol. 6, Issue 252, p. 252. ra120. DOI: 10.1126/scitranslmed.3008791.

11. Steenbergen L, Sellaro R, van Hemert S, Bosch JA, Colzato LS. A randomized controlled trial to test the effect of multispecies probiotics on cognitive reactivity to sad mood. Brain Behav Immun. 2015 Apr 7. pii: S0889-1591(15)00088-4.

12. Jarrett RB, Minhajuddin A, Borman PD, Dunlap L, Segal ZV, Kidner CL, Friedman ES, Thase ME. Cognitive reactivity, dysfunctional attitudes, and depressive relapse and recurrence in cognitive therapy responders. Behav Res Ther. 2012 May;50(5):280-6. doi: 10.1016/j.brat.2012.01.008.

13. Premysl Bercik, G. De Palma, P. Blennerhassett, J. Lu, Y. Deng, A. J. Park, W. Green, E. Denou, M. A. Silva, A. Santacruz, Y. Sanz, M. G. Surette, E. F. Verdu, S. M. Collins. Microbiota and host determinants of behavioural phenotype in maternally separated mice. Nature Communications, July, 2015. 10.1038/ncomms8735.

14. Sophie Leclercq, Firoz M. Mian, Andrew M. Stanisz, Laure B. Bindels, Emmanuel Cambier, Hila Ben-Amram, Omry Koren, Paul Forsythe, John Bienenstock. Low-dose penicillin in early life induces long-term changes in murine gut microbiota, brain cytokines and behaviour. Nature Communications 8, Article number: 15062 (2017). doi: 10.1038/ncomms15062. Published online: 04 April 2017.