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Probiotics 101

There are 10 times more bacteria living inside your intestine, than the entire number of cells in your body. That’s as much as 5,000 billion bacteria in every 5ml of intestinal contents. But these bacteria (around 400 species of them) are good, and far from causing diseases, which we usually associate bacteria with, these microscopic intestinal residents help prevent diseases. In fact, their mere presence prevents unhealthy bacteria from growing and multiplying inside us. This is known as the barrier effect, and without it our bodies would become overgrown with potentially fatal disease-causing bacteria. And they do a lot more than merely keeping your digestion regular by helping to prevent both diarrhoea and constipation. These bacteria also produce vitamins, most importantly vitamins K, B12, biotin and folic acid, which our bodies then absorb and utilise. Additionally, they help reduce cholesterol, keep your immune system functioning optimally and prevent allergies. Newer research shows that these bacteria can even help reduce stress, boost good mood and help prevent cancer.

Because of their beneficial effects, these bacteria have become known as pro (for) biotics (life) and that’s no understatement, since they’re essential for a healthy life. They’re also sometimes referred to as the forgotten vitamin. Offering a myriad of health benefits, they should form part of any good daily health supple- mentation programme.


Of the many species of probiotic bacteria residing in the intestine, the two most important ones are Lactobacillus, which reside mainly in the small intestine; and Bifidobacteria which colonise the colon (also known as the large intestine). The small and large intestines perform very different functions in the body.

Food is digested and broken down into protein, carbohydrates, and fats (including cholesterol) in the small intestine. It then absorbs these and all other nutrients such as vitamins and minerals into the body. Waste from within the body is also pumped into the small intestine from the liver. Other than a few vitamins, no food or nutrients are digested by, or absorbed from, the large intestine. Its only function is to absorb water into the body, making the waste more solid in the process, before it passes out of the body.

Lactobacillus, the small intestine resident, is mainly responsible for producing vitamins, reducing cholesterol absorption, and keeping the immune system healthy – an important function because the immune system isn’t only responsible for fighting infections, but cancers too. And if the immune system malfunctions, it can attack the body’s own tissues, causing what are known as autoimmune diseases. Because of their immune benefits, probiotic supplementation forms an important part of the natural treatment and prevention of thyroid disease, arthritis, cancers, and infections, and even the common cold.

Bifidobacteria, the colon-coloniser, promotes healthy bowel movements by preventing diarrhoea, constipation and irritable bowel syndrome. It also produces some vitamins and ensures that the tissue of the large intestine remains healthy, and it provides a barrier effect, preventing the growth of disease-causing bacteria and yeasts, such as Candida. This barrier effect also prevents the growth of bacteria that produce nitrosamines, a well-known cause of many cancers.


Research published at the end of 2011 showed that probiotics may help relieve depression and anxiety. Although these studies were performed on mice and still need to be replicated in humans, we’ve known for many years that the intestine and brain share common neurotransmitters, serotonin and melatonin. Serotonin is responsible for mood, while melatonin regulates sleep and is a powerful antioxidant. This brain-gut link is easily demonstrated by the fact that extreme anxiety causes diarrhoea and butterflies in the stomach. And people often describe a traumatic event as gut-wrenching. Many bowel disorders are caused by stress. So scientists decided to test this gut-brain hypothesis on mice. Mice that were given Lactobacillus probiotics showed significantly reduced stress-, anxiety- and depression- linked behaviour. And importantly, they produced less stress hormones too. Although it’s too early to recommend dumping your antidepressant in favour of probiotics, adding a Lactobacillus probiotic to your daily health regimen may help put that spring into your step. And there’s no reason not to combine it with your current antidepressant, since there are no interactions to be concerned about.


Lactobacillus, Bifidobacteria and other probiotic bacteria grow naturally in your intestine. However they require a healthy high-fibre, plant-rich diet to flourish (they consume fibre as their food source). Diets high in animal fats and protein, and low-fibre carbohydrates can reduce their numbers, and alcohol and smoking are also big bacteria killers. In such cases, supplementation with a good probiotic on a regular daily basis is a good idea. And obviously antibiotics will kill them too; so it’s especially important to take a probiotic during and after antibiotic use (for at least two weeks afterwards). If you suffer from irritable bowel or digestion problems, or any immune system related problem, then it’s also a good idea to supplement with probiotics. Although yoghurt is traditionally known for its probiotic content, there have been numerous reports that many types of yoghurt don’t contain the amount of probiotics needed.

Some supplements don’t supply enough either. You should supplement with a minimum of 1 billion probiotic bacteria daily. The number of probiotics in a supplement is sometimes referred to as “cfu”, which stands for colony forming units. Although 1 billion cfu is the minimum, research suggests that higher doses offer more health benefits. A dose of 10-20 billion cfu daily is ideal for most people; although some (eg. people with irritable bowel syndrome) can require higher doses.


Although Lactobacillus and Bifidobacteria are the most common probiotics, two others do deserve a mention:

  • Bacillus coagulans The only genuinely heat-stable probiotic, because it’s given in a dormant spore-form, which germinates in the acidic liquid in the stomach. It shares some of the health benefits of Lactobacillus and Bifidobacteria, mainly immune system support and promoting healthy bowel movement
  • Saccharomyces isn’t actually bacteria at all. It’s yeast, but qualifies as a probiotic because it provides a barrier effect against unhealthy bacteria, and promotes healthy digestion. Since it’s yeast, it’s not destroyed by antibiotics (antibiotics only kill bacteria). This makes it an ideal probiotic to use during antibiotic therapy.

References include

1 Natural Medicines Database; 2012; Therapeutic Research Faculty
2 Javier A.; Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve; PNAS August 29, 2011
3 Jurenka JS.; Bacillus coagulans: Monograph; Altern Med Rev. 2012 Mar;17(1):76-81. Review
4 Report of a Joint FAO/WHO Expert Consultation on Evaluation of Health and Nutritional Properties of Probiotics in Food Including Powder Milk with Live Lactic Acid Bacteria; WHO, 2001

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