Probiotics are beneficial bacteria and are required for optimal health. There are over 400 strains of bacteria that reside in the intestines. Researchers are just beginning to understand the roles in which these bacteria play in health and disease. It is well-established that these beneficial bacteria have a local effect on the health of the intestines where they compete with pathogenic bacteria, improve the barrier function of the intestines and modulate the immune response.1 Commonly supplemented strains of probiotics include Lactobacillus and Bifidobacterium strains, such as Lactobacillus GG, Lactobacillus acidophilus, Bifidobacterium bifidum, Bifidobacterium longum and Bifidobacterium infantis.
Recent research is now discovering that these bacteria are important in many other conditions such as obesity, anxiety and depression, allergies and possibly even diabetes and elevated cholesterol levels. Interestingly, a recent study found that fruit flies may choose their mates based on which flies have identical gut flora after eating similar diets, which demonstrates the wide variety of roles that these microbes play.2
Probiotics and Mood
An interesting study was recently published that suggests that probiotics impact mood and stress. Previous research has shown that Bifidobacterium longum and Lactobacillus strains decrease stress-induced gastrointestinal discomfort. This study led researchers to investigate probiotics for mood and reactions to stress. In this study, both mice and humans were treated with Bifidobacterium longum and Lactobacillus strains of probiotics. The mice were supplemented with the probiotics for 2 weeks and then evaluated for anxious behavior. In the clinical trial, humans were supplemented with the probiotics or placebo for 30 days. Following the supplementation, the subjects were evaluated with several questionnaires for stress and anxiety including Hopkins Symptom Checklist, the Hospital Anxiety and Depression Scale, the Perceived Stress Scale, the Coping Checklist and 24-hour urinary free cortisol, which is a measure of the stress response. The results of this study showed that in both the mice and humans, probiotic supplementation resulted in decreased measurements of stress and anxiety, as well as depression and anger-hostility in humans.3
Several animal studies have revealed similar findings. In one study, the probiotic Bifidobacterium infantis was investigated in rat maternal separation, which commonly produces anxiety and behavioral problems in the offspring. The study found that supplementation with this Bifidobacterium strain resulted in reversal of the behavioral deficits, normalization of the immune response and restoration of the concentration of the neurotransmitter noradrenaline in the brainstem. The authors of this study concluded, “These findings point to a more influential role for bifidobacteria in neural function, and suggest that probiotics may have broader therapeutic applications than previously considered.”4
Similarly, another study showed that the probiotic Bifidobacterium infantis modulates chemicals in the brain associated with depression in rats. This study found that Bifidobacterium decreased pro-inflammatory cytokines and increased plasma concentrations of tryptophan, which is the precursor to the mood-enhancing neurotransmitter serotonin.5 The ability to reduce pro-inflammatory cytokines is important for mood, as elevated concentrations of these cytokines are associated with major depressive disorder. This finding has led some researchers to propose that probiotics may be an adjuvant to standard care for major depressive disorder.6
Another study suggests that probiotics may support memory when under stressful conditions. In this study, mice were infected with an intestinal pathogen and assessed for memory formation under normal conditions and stressful conditions. Some of the mice were also supplemented with probiotics during the infection. The study found that under normal conditions, there were no behavior changes in the mice with the intestinal pathogen. However, under stressful conditions, the mice showed behavioral changes indicating memory dysfunction. Pre-treatment with probiotics was able to attenuate the memory dysfunction under the stressful conditions.7
Weight Management and Metabolic Disorders
Research suggests that intestinal microflora may modulate inflammation in obesity, diabetes and the metabolic syndrome.8 Researchers propose that this is due to the ability of the bacteria to influence regulation of energy uptake from the gut by digesting otherwise indigestible starches in the diet; production or activation of metabolic signaling molecules; modification of gut permeability; and the release of gut hormones and inflammatory mediators.8
Furthermore, research has shown that intestinal microflora differ between lean and obese individuals, as well as between diabetic and non-diabetic subjects.8 Further establishing the link between obesity and intestinal flora, a recent study investigated the role of the probiotic Lactobacillus rhamnosus GG and Bifidobacterium strains on weight gain in women during and after pregnancy. The women were randomized to a diet plus probiotic group, diet plus placebo group or the control group. The results showed that at 6 months’ postpartum, the women in the diet/probiotic group had a lower risk of central adiposity (fat deposition) compared to the diet plus placebo group or the control group.9 Another study investigated intestinal flora in overweight and normal-weight children. The flora was evaluated during infancy and the children were followed for 7 years to determine the development of obesity. The results of the study revealed that the children remaining normal weight in childhood had higher concentrations of fecal Bifidobacterium during infancy compared to the children that became overweight. Additionally, in the children that became overweight, there was an association with a greater number of the pathogenic bacteria Staphylococcus aureus compared to the children that remained normal weight. The researchers suggest because the changes in microflora preceded the changes in weight, probiotics may provide a preventive and therapeutic weight management strategy.10
Animal models have also shown that supplementation with Lactobacillus GG in diabetic rats resulted in significantly lowered blood hemoglobin A1c, which is a marker of blood glucose levels over the previous 3 months, as well as improved glucose tolerance compared to diabetic rats that were fed a standard diet without probiotics.11 In another interesting study, a milk product containing Lactobacillus acidophilus and Bifidobacterium longum was evaluated for effect on plasma lipids in women. The study found that in the women with elevated low-density lipoprotein (LDL)-cholesterol over 190 mg/dl, there was a significant reduction in plasma LDL concentrations in the women consuming the probiotics.12
Numerous studies indicate that probiotics influence the immune response in the gut resulting in supporting the health of people with allergic diseases such as atopic dermatitis, allergic rhinitis (inflammation of the nose) and airway reactivity. In one study, children with atopic dermatitis, which is an allergic skin condition, were supplemented with Lactobacillus acidophilus DDS-1, fructo-oligosaccharide and Bifidobacterium strains or placebo for 8 weeks. The study found that the children supplemented with the probiotics had a reduction in the atopic dermatitis according to the Scoring of Atopic Dermatitis value by 33.7 percent, compared to 19 percent reduction in the placebo group. In addition, during the supplementation period, the children in the probiotic group reported decreased use of corticosteroids to treat their condition.13 Another study found that supplementation with Lactobacillus acidophilus, Bifidobacterium bifidum and other Bifidobacterium strains in mothers during pregnancy and up to 6 months postpartum was effective at reducing the development of atopic dermatitis (eczema) during the first year of life in breastfed infants at increased risk for developing the disease.14
A review of published clinical trials with allergic rhinitis showed that 9 of 13 randomized controlled trials indicated that probiotics improve allergic rhinitis, resulting in lower symptom scoring and medication use with probiotic supplementation compared with placebo.15 Animal models also show that supplementation with Lactobacillus rhamnosus GG and Bifidobacterium strains reduce airway reactivity and modulate the immune response associated with asthma and allergies including reducing immunoglobulin E production, eosinophils in the lungs and the production of pro-inflammatory mediators.16
Probiotics including Lactobacillus acidophilus, Bifidobacterium bifidum, Bifidobacterium longum, Bifidobacterium infantis, and Bacillus coagulans (all found in BioPRO™) are playing an emerging role in many aspects of health. Research has shown that some of these strains are indicated for weight management, mood support and to modulate inflammation. Additionally, Lactobacillus GG, found in Culturelle®, has been shown to be helpful in weight management, immune support, and blood sugar maintenance. Inflammatory conditions such as lipid abnormalities, allergic conditions, and even anxiety and depression may be influenced by probiotics, with optimal balancing of the gut microflora occurring during probiotic supplementation.
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