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Background: Probiotics are live microorganisms that have positive effects on the host when consumed in sufficient amounts. According to several studies, probiotics have beneficial effects on prevention and treatment of many diseases. The aim of this study was to review animal and human studies on the role of probiotics in reducing serum cholesterol, their mechanisms of action, and a brief explanation of functional probiotic foods. Materials and Methods: This review article focused on all papers indexed in scientific databases from 2000 to 2012 using the related keywords, including cardiovascular diseases, probiotics, and serum cholesterol. Results: Probiotics are used both in dairy and non-dairy products. Nowadays, the role of many probiotic strains in health is confirmed. From the studies done in this field, it can be inferred that probiotics through several mechanisms, such as binding cholesterol to cell walls of probiotics in intestine, conversion of cholesterol into coprostanol, production of short chain fatty acids, and deconjugation of bile acids, reduce serum cholesterol. Conclusion: Certain strains of probiotics have demonstrated cholesterol-lowering properties and others are under study. Further studies are needed to identify other mechanisms involved in lowering serum cholesterol and determine their safety

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Background: Obesity, the most common health problem, can result in the incidence of many chronic diseases. genetic and environmental factors can affect its incidence. Differences in the population of gut microbiota in lean and obese subjects and interaction between them, has led to a field of investigation about the effects of intestinal microbiota in the obesity occurrence. In the other hand, the use of functional foods has been shown positive effects in the prevention of obesity. This study was aimed to assess the differences between gut microbiota in obese and normal people, their roles in energy homeostasis and the mechanisms of probiotics and prebiotics in the management of obesity.

Materials and Methods: All articles indexed in the valid scientific data bases published between 2000 And 2014 were Searched and reviewed using probiotics, prebiotics, obesity and gut microbiota as key words and results were examined.

Results: A group of gut microbiota facilitates energy extraction from the diet that results in fat storage in adipose tissues. bacteroidetes as a residing bacterial in the gut is in fewer amount, inversely, firmicutes as another residing bacterial is in higher amount in obese people, and it changed in lean individuals, inversely. Differences in the extraction of energy in subjects were attributed to differences in the composition in gut microbiota. archaea ‌species that resident in the gut involved in energy homeostasis through increasing the ability of fermentation, electron production and removing the energy. In addition to, the probiotic and prebiotic supplements have roles in the prevention of obesity via stimulating the growth of beneficial bacteria, production of short chain fatty acids, modulating the secretion of hormones involved in energy homeostasis.

Conclusion: Further studies are needed to identify the specific probiotic bacteria and other effective functional foods in management of obesity.

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Background: Constipation is a functional gastrointestinal disorder and the use of probiotics is considered as a new solution in prevention and treatment of constipation. The aim of this study is to review the clinical evidence about probiotics effects in the prevention and treatment of constipation.

Materials and Methods: To review the accessible evidence about efficacy of probiotics in the prevention and treatment of constipation, the search of key words such as constipation, probiotic and yoghurt are conducted in databases Pubmed, Medlinplus and Cochran from 1980-2013 and of 49 articles about constipation, 16 yandomized controlled clinical trial articles and 3 pre-test and post-test randomized trials that investigated the effects of probiotics on constipation were included in this study.

Results: Probiotics produced lactic acid and fatty acids with short chains that decrease the colon pH and stimulate muscular contractions and intestinal peristalsis. Some of probiotics can increase the mucous discharge and change linked bile salts to free bile salts entering much water to colon and leads to soft defecation.

Conclusion: Considering studies, daily use of probiotics such as lactobacillus acidophilus and bifidobacteria lactic 10⁵-10¹¹ CFU/gr for at least 1-2 weeks can help to decrease constipation.

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Background: Metabolic syndrome, a concurrence of overweight and abdominal fat distribution, disturbed glucose and insulin metabolism, mild dyslipidemia and hypertension is among the most important issues that man deals with, in today's world. Probiotics are live microorganisms which, when administered in adequate amounts, can confer a health benefit on the host. The aim of the present study was to review the clinical evidence available regarding the role of probiotics in improvement of disorders associated with metabolic syndrome.

Materials and Methods: In this research, clinical trials performed between 2000-2014 were searched in two databases, Pubmed and ScienceDirect. In both databases “Probiotics”, “metabolic syndrome” and each of its elements were used as the key words.

Results: Probiotics may reduce body weight through manipulating the gut flora. Through reducing inflammation and immune-regulation, probiotics decrease insulin resistance. They also improve lipid profile through reducing cholesterol absorption and producing short chain fatty acids, as well as deconjugating bile acids and converting cholesterol to coprostanol. Moreover, probiotics have been suggested to have a hypotensive effect through release of angiotensin-converting enzyme inhibitory peptides, through proteolytic action. 

Conclusion: Although some clinical trials have failed to obtain beneficial effects of probiotics on metabolic syndrome related situations, a majority of the studies have shown positive results for these microorganisms in this regard. Thus, probiotics can be looked upon as a novel approach when either prevention or alleviation of metabolic syndrome is aimed.