Good Gut Bacteria, Health and Weight Control

At last count, scientists estimate that around 750 trillion bacteria, yeast and other microorganisms inhabit a healthy digestive system. Friendly flora species include Escherichia, Lactobacillus, and Bifidobacterium. Other common inhabitants include Bacteroides, Clostridium, Fusobacterium, Eubacterium, Streptococcus and certain yeast (Candida) strains. Individual species inhabit certain sections of the GI tract and target certain sugars, proteins or fats for digestion. Scientists have only decoded about 10% of friendly gut flora, but even these preliminary data prove how dependent we are on them.
The term probiotics, refers to foods or supplements containing live beneficial microbes, primarily bacterial strains, that are used to fortify or rebuild our natural gut flora.

Which are the probiotic foods (i.e which foods contain active cultures of beneficial bacteria)?
fermented vegetables (sauerkraut, artichokes)
fermented fruit (olives)
fermented meat (salami)
fermented legumes (soy sauce, miso,tempeh)
fermented milk (kefir, feta cheese, buttermilk, sour cream and yogur).
fermented drinks (yakult)

In Australia only some yoghurts (e.g Vaalia, Jalna) have large numbers of live bacteria (>1 million per gram of yoghurt) when they reach supermarket shelves - these large numbers are needed to ensure some good bugs get to the large intestine.

The first beneficial microbe in our gut, Bifidobacterium infantis, is introduced through breast milk during the initial days of life, helping us digest milk sugars. As we mature, other species, like Lactobacillus, colonize the intestines

When we are healthy, it is in large part because our digestive system is healthy via the 'good' gut bacteria.

Called beneficial flora, these small friends digest and help us absorb our food, they improve our immune systems, even contribute to the manufacture of vitamins (B vitamins and vitamin K). Acidophilus and Bifidobacterium strains increase the bioavailability of minerals that need short-chain fatty acids for absorption, such as magnesium, iron, copper and manganese. They also break otherwise indigestible carbohydrates down into short-chain fatty acids, providing us with energy and nutrients. Other forms of bacteria digest proteins, freeing up amino acids for absorption.

What affects the balance of microorganisms in the gut?
Illness
stress
medications
antibiotic use
reduced speed of peristalsis (the wave-like action of the digestive system) due to lack of physical activity or long term use of laxatives or medications (narcotics,antidepressants, calcium channel blockers, iron supplements).
not eating enough probiotics
not eating enough prebiotics

Impaired or imbalanced intestinal flora are implicated in:
obesity
Recent animal studies suggest that a lack of good bacteria in the gut is linked to weight gain in these animals and obese humans have been found to have less good bacteria than lean people. Researchers are not sure what the mechanism is but good bacteria are known to breakdown plant compounds (thiocyanates) that can adversely affect thyroid function (the thyroid controls your metabolic rate). There are probably several other mechanisms involved.

heart disease, elevated cholesterol
Some good bacteria target the digestion and storage of fat, helping us normalize our cholesterol and triglyceride levels by helping with the circulation of bile and its detoxification.

allergies and asthma
skin disorders
IBS and digestive problems
diarrhoea/constipation
some cancers
Alzheimer's and much more

Taking probiotics for these conditions may help with their treatment but the evidence is far from conclusive that they are effective (except for diarrhoea where the evidence is convincing that they help).

Indications for probiotic use
GI sensitivity (cramps, diarrhea/constipation)
Bloating or foul-smelling gas
Good intestinal flora regulate bowel movements, and help prevent bloating, gas, and yeast overgrowth by controlling the pH level of the intestines through production of lactic acid. In babies, they stem diaper rash, diarrhea, and colic, as well as preventing allergies.
Dysbiosis, intestinal inflammation, including irritabe bowel syndrome and partially-digested stools
Recent research has shown that inflammation in the small bowel is frequently caused by immune cytokine tumor necrosis factor alpha (TNF-alpha) which causes an increase in gut permeability i.e where the cells lining the gut do not form tight junctions) leading to 'leaky gut syndrome'. If the gut is permeable then more allergens can enter the blood stream and there is extra load on the liver. Good gut bacteria can help decrease gut permeability.
Yeast infections, thrush, cold sores, diaper rash
Headaches, migraines, joint aches
Chronic bad breath/halitosis
Good bacteria produce natural antibiotics and antifungals; for instance, Streptococcus salivarius manufactures an antiseptic that neutralizes the sulfur compounds responsible for bad breath (halitosis). Friendly flora also keep unfriendly bacteria in check by depriving them of nutrients and secreting acids (acetic, lactic, and formic) that create a hostile environment for pathogens.
Rosacea, acne
Fatigue, irritability
Anorexia and/or bulimia
Stuffy nose, increased mucus production
Some bacteria have a stimulating effect on the immune system, by increasing T-cell counts, for example. In a recent study reported by the Annals of Nutrition and Metabolism, the number of certain T-lymphocytes that target cytotoxins (T2, T3 and T4) jumped by more than 28% in healthy young female test subjects after they ate conventional yogurt daily for one month.
Increased symptoms of PMS, perimenopause, or menopause
Beneficial flora metabolize and recycle hormones, including estrogen, thyroid hormones, and phytoestrogens from food sources, which can help offset symptoms of menopause, PMS and perimenopause. In this way, they help maintain proper hormonal balance, and may protect bone and breast health as well. There is evidence that some probiotics may have anti-tumor, anticancer effects by helping us metabolize specific food components (like antioxidants and flavonoids) into useable forms.
Worsening sensitivity to sugar and fermented products
Worsening symptoms of inflammatory conditions, like asthma, allergy, dermatitis, eczema, rheumatoid arthritis
Beneficial bacteria reinforce the mucosal barrier of the intestines (reducing gut permeability), which is associated with the gut-associated lymph tissue (GALT), helping to prevent pathogens, toxins and allergens from entering the rest of the body. In this way, their presence "teaches" the immune system which allergens and toxins are tolerable and which need to be disposed of.

(Although many of the above symptoms can indicate floral imbalance, they can also indicate more serious conditions. See your doctor with any ongoing concerns.)

Which are the prebiotic foods (i.e whih foods provide nutrition to the good bacteria)?
Prebiotics help probiotics survive passage through the acidity of the stomach and foster their growth in the intestines and colon. Prebiotics are just as important as the bugs themselves.

Good bacteria feast on the following prebiotics:
fiber (e.g psyllium husk)
resistant starch (e.g sticky Japanese rice)
certain sugars e.g fructooligosaccharides (FOS), and inulin, which are natural sugars found in bananas, chicory root, onions, leeks, fruit, soybeans, sweet potatoes, asparagus and some whole grains.

Prebiotics have also been reported to be effective for use in the treatment of constipation.

Given a ready supply of vegetables, legumes and whole grains, good bacteria live long and prosper, pushing out the bad bacteria (E. coli and Staphylococcus aureus). .

Polyphenols (antioxidants), found in foods like garlic, green tea and ginseng, are also helpful in fostering friendly flora. The bad bugs love refined sugar and animal fat.

We are only just beginning to understand how these prebiotic saccharides work in the gut to impact our health and longevity. Foods high in inulin and fructooligosaccharides have been shown to lower cholesterol levels, stabilize blood sugar, and improve calcium absorption. The mechanism proposed for the latter benefit is that prebiotics decrease the pH in the colon, making it more hospitable for certain beneficial gut flora, which in turn do the job of absorbing any calcium remaining in the food by the time it gets to the colon. Though we don't understand all the steps in this process or whether the effects hold true across a lifetime, we do see a positive association between a diet high in these foods and higher bone density, with the expected decreased risk for osteoporosis.

Learning from Traditional Cuisines
Most successful traditional cultures regularly consume both pre and probiotics e.g Asians eat soy sauce + rice + tofu +garlic + onions+green tea, Mediterraneans eat yoghurt/feta + legumes + garlic + onions + olives +herb teas and MiddleEasterners eat Kefir + psyllium husk.

Recommendations - try to have some pre and probiotics daily for a healthy gut - and maybe it will also help with weight management, cholesterol, skin and gut problems, bad breath, PMT, joint and head pains! Sounds to good to be true. If you prefer supplements, probiotic supplements can be purchased from most pharmacies and reports indicate that they are safe and do not pose an infection risk.

Last Updated: April 2007