Monday, December 05, 2005

Probiotic skepticism.

In one of those occasions that I decide to watch some TV, I couldn't help but notice an ad for a milk formulation that claims to add a 'probiotic' to the milk. This 'probiotic' claims to help aid your immune system, digestion and prevent 'bad' bacteria from doing stuff to you. These sorts of products are starting to leave the obscure 'self-treatment' health stores and begin to appear more widely in every day brands from supermarkers. It's important to hence ask the question of what is a probiotic actually supposed to be and importantly from a skeptics point of view, does it actually do what they claim?

Probiotics are a concept that's been around for some time now since the late 1800s from Elie Metchnikoff; winner of a Nobel prize for his work on phagocytosis and who also happened to have an interest in the reasons why people age. One of the things that he noticed was people from Bulgaria who ate a lot of fermented dairy food products, such as yoghurt appeared to be longer lived. Metchnikoff thought that this was due to the addition of specific bacteria from these foods that outcompeted and prevented the 'toxin' producing bacteria from establishing. As a result for a while in Europe it was quite popular to have milk that had "Bulgarian bacillus" added to it. This addition of potentially beneficial bacteria to foods was the birth of 'probiotics' and has been developed upon ever since(1).

Possibly as a result of Metchnikoffs original observations, the bacteria typically used in probiotic treatments are of the genus Lactobacillus. Lactobacilli are fairly hardy organisms that are usually acid tolerant or acid loving. They are particularly common in fermented foods where the acid- notably Lactic acid - they produce as a metabolic by-product destroys other bacteria that would otherwise compete with them. Basically if you've ever eaten yoghurt, cheese and those sorts of foods you've basically eaten a large amount of Lactobacilli. Additionally if there was a candidate for Mrs. probiotic it would probably be Lactobacillus acidophilus. It's used in a wide range of products, such as milk, yoghurt (most commonly) and powder to stick in water. The claims made from the site in question are fairly common among probiotic advocates:

Product Description
Natren's Superdophilus benefits the small intestines of older children (over 7 years) and adults, and the vaginal tract of women. DDS-1 Super Strain is the most highly recommended of approximately 200 different known strains of L. acidophilus - many other strains cannot survive human gut fluid and bile salts. DDS-1 has been shown to be the most effective against the widest number of pathogens (disease forming microorganisms). Minimum 2 billion live active bacteria per gram (half teaspoon).

General Information
It is very important to replace your friendly bacteria after antibiotic use, steroidal drugs e.g. prednisone and birth-control pills with Superdophilus. Superdophilus generally aids your absorption of nutrients and may help deter invading bacteria and yeasts by producing natural antimicrobial substances and hydrogen peroxide - this strain effectively inhibits undesirable microorganisms that cause food poisoning, diarrhoea, yeast and thrush overgrowth (Candida). Assists lactose (found in dairy products) metabolism so enhances digestion of milk products - helps dairy food intolerance.

Sounds all well and good doesn't it, after all something that does even half of what is claimed would surely be a great benefit to a large number of peoples health. Of course, these products have to work by the bacteria in question establishing themselves and basically making a home in your stomach. If the bacteria don't get established in there then any benefit will be temporary or probably null and void. Additionally, a gut insult that disrupts the microflora* or makes things unstable may be equally as hostile to a newcomer and end up with no effect anyway. To assess the claims made above is actually surprisingly simple because the only question that needs to be answered is this: How easy is it to introduce and establish a new organism in a host?

The answer? Bloody difficult. The one problem facing probiotics as a treatment or novel health supplement is that the established existing microflora doesn't take too kindly to the new comer (1, 2, 3, 4). In fact, the additional bacteria are only temporary and can only be detected for the period that the probiotic is being taken (3). This is because the gut microflora tends to end up in an homeostatic state where what bacteria got established first tend to stay there. Interestingly, this microflora tends to also rebound in the same sort of numbers even when it has been depleted, say after taking a broad spectrum antibiotic (the tiny scale equivalent of nuking all of Iraq to kill a handful of insurgents). It's also fairly unique and everyone will have slightly different compositions of bacteria in their gut, creating a unique 'poo-print' that identifies your insides as much as your finger print identifies your outsides. It's worth noting that detection of the probiotic bacteria says nothing about the number of bacteria that are actually there or doing anything in particular (1, 3, 4).

It is also questionable as to what these bacteria are doing even while they are present in the gut. Although there is research to suggest that gut bacteria are interacting with the hosts immune system (5) the actual extent of this interaction is relatively poorly understood (1). In fact, it isn't actually very clear what benefits probiotics may have at all (1, 3). While a lot of basic research has been conducted on the organisms responsible, there have been no rigourous medical or clinical studies performed on humans to assess the overall benefits these organisms may have. This is particularly true of meeting FDA (Food and Drug Administration) guidelines as the required phase I-IV trials have never been conducted on these probiotic organisms (1). Of course, it's worth noting that they can still be marketed with the above sorts of claims despite this, because Lactobacilli are "GRAS" organisms or "Generally Regarded as Safe" so haven't been put to the same vigourous review for a new treatment.

Although there are promising studies that have suggested probiotics can be effective, they are increasingly focusing on using specific bacteria for specific disorders and not the 'blanket' benefits as the advertising claims quoted above would have consumers believe. At the current moment probiotics are an interesting but very definitely unproven concept. With the expense of many of these new probiotic bearing foods over the normal ones, such as Acidophilus yoghurt which can cost twice as much as the regular product my advice is fairly simple. If you can afford it you are probably not going to be any worse off trying these probiotic products, but otherwise just buy the regular items until they have more definitive clinical studies to support their supposed health benefits.

*Microflora refers to the bacterial community in the gut, usually composed of a wide array of different species.

1) Tannock G.W. A Special Fondness for Lactobacilli (2004). Applied Environmental Microbiology, 70(6);3189-3194 (Free text available)

2) Tannock G.W. (2003). Probiotics: Time for a dose of realism. Current Issues in Intestinal Microbiology, 4(2);33-42.

3) Tannock G.W., K. Munro, H.J.M. Harmsen, G.W. Welling, J. Smart and P.K. Gopal (2000). Analysis of the Fecal Microflora of Human Subjects Consuming a Probiotic Product Containing Lactobacillus rhamnosus DR20. Applied Environmental Microbiology, 66(6);2578–2588. (Free text available)

4) Jenkins B., S. Holsten, S. Bengmark and R. Martindale (2005). Probiotics: a practical review of their role in specific clinical scenarios. Nutrition in Clinical Practice, 20(2);262-70.

5) Mohamadzadeh M., S. Olson, W.V. Kalina, G. Ruthel, G.L. Demmin, K.L. Warfield, S. Bavari and T.R. Klaenhammer (2005). Lactobacilli activate human dendritic cells that skew T cells toward T helper 1 polarisation. PNAS, 102(8);2880-2885. (Free text available).