Dr John Wright



Leeches and Probiotics

Dr John P Wright
Updated: 2 August 2010

Hippocrates (460BC - 370BC) was the thinking man’s physician. His influence has lasted. He was a man of his time. When he looked at the human predicament he interpreted it in light of the information available. One unique observation was that when blood clotted it formed layers. Firstly a pure red liquid then a yellow coloured serum, a white material which is the leucocytes and finally a black substance which was the clotted blood. He however did not interpret this as we do now. On the evidence he had he recognized these components as the very essence of man, red blood, yellow bile, phlegm and black bile. These were the four humors and correlated with the health of his patients and the whole world view of the time:


Earth (cold, dry)
Water (cold, wet)
Air (warm, wet)
Fire (warm dry)


Black bile
Yellow bile







Emotional tendency

Prone to sadness
Prone to apathy
Prone to optimism
Prone to anger

With this view the evidence suggested that a stable healthy person had the right balance of humors and conversely the diseased were out of balance. It was up to the physician to re-adjust this situation in his/her patients. A patient with a pyrexial disease was warm and wet and therefore had to much blood so blood letting would be indicated. If that did not help you might be able to induce a cold dry state by giving the patient black bile from a sheep’s gallbladder. If that also failed emergency bloodletting might be needed. It is said that George Washington was bled to death by his physicians in 1799 who are said to have drained 5 pints in a last desperate effort to save him from his pneumonia.

This paradigm of humor manipulation continued from 400BC to the early 1800’s. Hippocrates’ mother must be proud of her son. It does however show that even highly intelligent people are not immune from creating a belief system on the basis of an optimistic misinterpretation of the facts. In1628 William Harvey showed that blood circulates and that the humors leaking out through the skin was just untrue. This discovery was not accepted by the profession with any enthusiasm as the treatment of George Washington 170 years later shows. A deeply held belief is not easily dispelled by the facts.

This brings us on to the new leeches, the probiotics. The use of probiotics is also based on a sound observation. Bacteria cover our bodies both on the skin and in the intestine. Diseases from acne to typhoid can be attributed to a bacterial imbalance. It therefore stands to reason that if we can manipulate our bacterial populations back to a healthy balance we to will in turn be healthy.

Like Hippocrates’ knowledge of blood, our knowledge of our bacterial co-travellers is woefully inadequate.

Although we have advantageously lived together for hundreds of thousands of years 70% of our intestinal bacteria are still of unknown variety. Our best attempts to manipulate our intestinal flora and fauna are of very short duration as the previous population usually re-establishes itself within 48 hours of intestinal cleaning or the introduction of probiotics.

So where did the idea of manipulating our intestinal bacteria come from. A Russian scientist, Eli Metchnikoff, working at the Pasteur Institute in Paris in 1907 believed that colonic bacteria produced toxins that caused aging and finally death. This he called auto-intoxication. At the time it was observed that fermented milk inhibited proteolytic bacteria. It was also known that some tribes, such as those in Bulgaria, who drank yoghurt, reached very advanced ages. He therefore postulated that it was the “fermented” milk that was responsible for their longevity. He then popularised yoghurt which was made with his “Bulgarian Baccilus”. Like Hippocrates, Metchnikoff based his belief on an astute, but fallacious, observation and the gullible, plebs and physicians ran with the idea.

The running can be measured by simply doing a Google search on probiotics, 6 960 000 hits returned in 0.22 seconds and on PubMed 7095 articles appear in a similar fraction of a second. So how can one evaluate the effect of probiotics with this information overload? Everyone from patient to manufacturer can produce supporting data but if one article is very supportive what about the other 7094, do they agree.

As an example of probiotic research, a 2004 study into maintaining remission with a probiotic, Escherichia coli Nissle in patients with ulcerative colitis it was found that after a year of treatment 36% of patients on the probiotic had relapsed compared to 33% of those on mesalazine 1.5G daily. The study concluded that the effectiveness of probiotic treatment further underlines the pathogenetic significance of the enteric flora. A conclusion that is difficult to base on the results which showed that the probiotics and the low dose mesalazine were marginally better than the expected placebo rate of 30%

Many reviewers are involved in the probiotics industry as users, researchers or producers, so as the car magazine editor has to temper his even mildly negative views on the test vehicles so those who are dependent on the probiotic movement need to protect their turf. One authority we could appeal to is the Cochrane Collaboration. A UK based organization that does evidence based meta reviews on many contentious topics.

The gastrointestinal areas most commonly treated with probiotics are irritable bowel, Infective diarrhoea, inflammatory bowel disease, pouchitis and for preventing allergies in children. What has the Cochrane Collaboration said about some of these indications over the last 2 years?

  1. Probiotics may be a useful adjunct to rehydration therapy in treating acute infectious diarrhoea.
  2. There is no evidence to support the use of probiotics in the treatment of C. difficile colitis
  3. There is insufficient evidence to make any conclusions about the efficacy of probiotics for induction of remission in Crohn's disease.
  4. There is no statistically significant differences in remission or clinical improvement rates in ulcerative colitis between probiotic and placebo or active comparator groups
  5. In treating acute or chronic pouchitis there is no evidence that probiotics are better than standard antibiotics
  6. For maintaining remission in chronic pouchitis a probiotic was better than placebo
  7. There is insufficient evidence to recommend the addition of probiotics to infant feeds to prevent allergic disease or food hypersensitivity

The use of probiotics in irritable bowel is widespread but in a review published in 2009 by the American College of Gastroenterology on the management of IBS it was concluded that Lactobacillus does not appear to be effective in single organism studies and studies involving combinations of probiotics, though Bifidobacterium demonstrates some efficacy in some situations.

In conclusion the objective data suggests that although probiotics may be “helpful” in some conditions the data is at best suggestive rather than proven. It is often stated that if probiotics do no harm and may help why not use them. This reduces the medical profession to snake oil salesman where truth is negotiable and integrity arbitrary. If we wish to avoid the blindness that led to George Washington’s death we need to adhere to the scientific basis of our profession and re-dedicate ourselves to evidence based medicine.