Functional foods are similar in appearance to conventional foods; the former being consumed as part of the normal diet. In contrast to conventional foods, functional foods, however, have demonstrated physiological benefits and can reduce the risk of chronic disease beyond basic nutritional functions, including maintenance of gut health. When food is being cooked or prepared using "scientific intelligence" with or without knowledge of how or why it is being used, the food is called "functional food". Thus, functional food provides the body with the required amount of vitamins, fats, proteins, carbohydrates, etc., needed for its healthy survival.

There is no question that breast milk is the best form of food for newborns and infants, and should be the number one choice for all mothers. However, some mothers are unable to breastfeed, which is why it’s important they have access to safe and nutritious alternatives. When it comes to infant formula, the aim and intent of the World Health Organisation (WHO) International Code of Marketing Breast Milk Substitutes is fully supported. Breast milk substitutes are recognised by the WHO as a safe and nutritious alternative to breast milk for infants whose mothers cannot, or choose not to, breastfeed. Probiotics are supplements or foods that contain viable microorganisms that cause alterations of the microflora of the host. Use of probiotics has been shown to be modestly effective in randomized clinical trials (RCTs) in (1) Treatment of acute viral gastroenteritis in healthy children (2) Prevention of antibiotic-associated diarrhea in healthy children. There is some evidence that probiotics prevent necrotizing enterocolitis in very low birth weight infants (birth weight between 1000 and 1500 g). The results of RCTs in which probiotics were used to treat childhood Helicobacter pylori gastritis, irritable bowel syndrome, chronic ulcerative colitis, and infantile colic, as well as in preventing childhood atopy, are also encouraging the use of probiotics for infants. 

In human nutrition, lactobacilli and bifidobacteria are frequently included in yoghurts and other milk products. However, due to their poor stability during storage, their application in animal nutrition is rather limited. Probiotic feed additives generally consist of one single strain or a combination of several strains of bacteria, Bacillus spores or yeasts species (multi-strain). Preparations authorised for use in animal nutrition in the European Union include different strains of Enterococcus, Bacillus, Lactobacillus, Pediococcus or Saccharomyces. The benefit of probiotics with respect to health status and performance is expected to be highest in young animals such as piglets, newly-hatched chickens or calves, because these animals have not yet developed a stable gut microflora. Moreover, when animals undergo therapeutic treatment of diseases with antibiotics, the gut microflora is generally decimated. Therefore, administration of probiotics after antibiotic treatment assists in re-establishing a beneficial gut microflora to prevent the host from recurrent pathogenic colonisation.

Silage inoculants is another important factor of animal nutrition which is helps in providing  aid for the process of fermentation by reducing the forage quality loss and helps in maintaining high quality feed and palatability that will also lead to improved animal performance thereby, extending the shelf life of silages. Spoilage microorganisms such as bacteria, yeasts, and molds readily grow on crops going into a silo, causing losses in dry matter and nutrient quality. Having an oxygen-free (anaerobic) environment and a low pH in the silo can prevent these organisms from growing. These spoilage microorganisms are also the culprits in poor fermentation. Efficient fermentation will conserve dry matter to boost feed value. Homofermentative lactic acid bacteria, such as Lactobacillus plantarum, Enterococcus faecium, and some species of Pediococci can improve the initial fermentation process by speeding up the production of lactic acid and limiting the production of unnecessary end products that may lower the efficiency of fermentation. Creating a desirable environment in the silo (low pH) can reduce protein degradation and prevent the growth of several microbes in the silage like Enterobacteria, Clostridia and molds

Probiotics are live microorganisms which confer a health benefit on the host when administered in an adequate amount. Over the past decades, the market size of probiotics has greatly increased as modern consumer concern about health-promoting effect of nutraceuticals. Since probiotic-containing products in general do not require Food and Drug Administration approval, they are commonly available in the market in various food formats such as fermented milk, cheese, yogurt and juice. In recent years, probiotics have been extensively studied as a treatment option of various diseases such as obesity, diabetes, cancer, human immunodeficiency virus infection, irritable bowel syndrome. For probiotics to exert beneficial activities, a sufficient amount of probiotics should be alive and functionally active at the site of action as well as in a product. Probiotics are recommended to be present at a minimum level of 6 log colony forming unit (CFU)/g in a food product or 7 log CFU/g at the point of delivery. Due to the vulnerability of probiotics to harsh conditions during manufacturing, storage and passage through the gastrointestinal (GI) tract, however, it is difficult that viable probiotics successfully exert beneficial activities. During manufacturing and/or storage, the viability of probiotics can be negatively affected by several factors such as temperature, water activity and other food ingredients. Specifically, high temperature during manufacturing processes is a main reason for reduced viability because most probiotics have low thermo-resistance. Maintaining viability in the stomach is another difficult task for probiotics to reach the target site because most of probiotics die or lose their functionality at acidic conditions. Next, survived probiotics should be released at the target site of action which is usually small or large intestine. Therefore, an ideal probiotic delivery system should protect probiotics from adverse conditions during fabrication and storage and in the acidic gastric environment so that the sufficient amount of probiotics is available in the site of action.

Our gut contains both beneficial and harmful bacteria.  Digestive experts agree that the balance of gut flora should be approximately 85 percent good bacteria and 15 percent bad bacteria. If this ratio gets out of balance, the condition is known as dysbiosis, which means there is an imbalance of too much of a certain type of fungus, yeast or bacteria that is affecting the body in a negative way. By consuming certain types of probiotics foods and supplements we can help bring these ratios back into balance. The efficacy of a probiotic effect often depends on the mechanism by which they exert their activity. By and large, to treat a disease, the probiotics follow a set of mechanisms, which is discussed in this review. The effective performance of the probiotic depends on their strong adherence and colonization of the human gut, which in turn improves the host immune system. The mechanism of adherence is still under investigation, but Lactobacillus plantarum 299v has been shown to exhibit a mannose specific adhesion by which it can adhere to human colonic cells. Once the probiotic adheres to the cell, various biological activities take place, which primarily include the release of cytokine’s and chemokine’s. These then exert their secondary activity such as stimulation of mucosal and systemic host immunity.

They are novel, clinically proven and safe molecules present in the market, whose health claims are approved by various international and/or Indian regulatory authorities. Probiotic-derived factors have been described as capable of exerting probiotic activities through probiotic mechanism of actions Although there are many bacteria-derived products capable of inducing a health benefit, the concept of probiotic is only attributed to microorganisms administered as viable forms, providing the opportunity for a symbiotic relationship between the host, and resident, or in-transit, microorganisms. Secreted probiotic factors, such as reuterin from Lactobacillus reuteri, have been reported to inhibit adhesion and viability of known enteric pathogens, suggesting that probiotic supernatants could be a rich source of new antipathogenic compounds.

People come into contact with probiotics used in animal nutrition in two ways, either as workers in the production of premixes and compound feeds, or as farmers during feeding. In both cases there are no hazards for the users. Comprehensive studies have shown that direct contact of the registered probiotic products with skin, mouth and nose do not compromise human health. In model trials it has been established that even long-term or increased exposure do not constitute a risk to health. In general, the microorganisms approved for animal nutrition have a very good safety record. Even in cases of overdoses of more than a thousand times the recommended levels in feed, there are no signs of dysbiosis in the gastrointestinal tract. Therefore, probiotics do not constitute any health hazard for the animal. Since they are not transferred from the intestine into the body of the animal, they do not affect any metabolic processes, nor do they have any negative impact on the animal. Having exerted their effect in the digestive tract, the probiotic reaches the exit of the intestine in the digesta, together with other intestinal microorganisms. On their way along the digestive tract the majority of the probiotic bacteria die off, since their growth and proliferation is severely restricted by competition from other microorganisms present in the large intestine. The development of yeasts is also suppressed by a lack of oxygen. The probiotics are already partly broken down and digested like other organic nutrients in the intestine so that only a small proportion is excreted viable in the faeces and survives in the manure to reach fields and grassland. Evidence of the harmlessness of the probiotic to the environment is one important subject for its registration. In general, any negative impact is highly unlikely since all these microorganisms are derived from nature. 

Any substance that is reasonably expected to become a component of food is a food additive that is subjected to premarket approval by FDA, so if a probiotic is intended for use as a drug, then it must undergo the regulatory process as a drug, which is similar to that of any new therapeutic agent. An Investigational New Drug application must be submitted and authorized by FDA before an investigational or biological product can be administered to humans. The probiotic drug must be proven safe and effective for its intended use before marketing. If a probiotic is intended for use as a dietary supplement, it is placed under the umbrella of “foods,” and as such is regulated by FDA’s Center for Food Safety and Applied Nutrition. In contrast to drugs, dietary supplements do not need FDA approval before being marketed. However, manufacturers need to notify FDA before marketing a product. According to Dietary Supplement Health and Education Act, 1994 (DSHEA), the manufacturer is responsible for determining that the dietary supplements that it manufactures or distributes are safe and that any representations or claims made about them are substantiated by adequate evidence to show that they are not false or misleading; the manufacturers need not provide FDA with evidence that substantiates the safety or purported benefits of their products, either before or after marketing. The law allows that in addition to nutrient content claims, manufacturers of dietary supplements may make structure/function or health claims for their products. For a structure/function claim, FDA requires that manufacturers’ substantiation is accepted by experts in the field and that the claim is truthful and not misleading. The data substantiating structure/function claims need not be publicly available and need not be disclosed.  In 2001, in an attempt to standardize the requirements needed to make health claims regarding probiotic agents, the Joint Food and Agriculture Organization of the United Nations/World Health Organization Expert Consultation on Evaluation of Health and Nutritional Properties of Probiotics developed guidelines for evaluating probiotics in food that could lead to the substantiation of health claims. The Consultation recommends that specific health claims on labeling material on probiotic food items be allowed when sufficient scientific evidence is available and that the product manufacturer take responsibility for ensuring that an independent third party reviews and evaluates the scientific evidence.

In addition to restoring the microbial balance of the Gastrointestinal Tract (GIT), products containing probiotic organisms, are also claimed to propose to have several dietary and therapeutic or functional benefits. Preventive and therapeutic effects of these agents have been observed in the lactose intolerance, constipation, hypercholesterolemia, lactose intolerance, virginities, intestinal infections and various cancers such as breast cancer, bladder cancer, colon cancer, liver cancer. But there are many challenges in the development of a probiotic food product such as strain selection, inoculation, growth and survival during processing, viability and functionality during storage, assessment of the viable counts of the probiotic strains particularly when multiple probiotic strains are added and when there are also starter cultures added, and the effects on sensory properties.

Probiotic microorganisms can shape the immune system both at the local and systemic level which will allow future probiotics as treatments for many diseases. Probiotics seem to have promising role in shortening duration of infections or decreasing susceptibility to the pathogens. Use of the different strains, dosage, duration of treatment and smaller size of the trials makes interpretation of the available data more difficult. Current evidence also indicates that probiotic effects are strain-specific, they do not act through the same mechanisms nor are all probiotics indicated for the same health conditions. It is currently unknown whether there are optimal probiotic species, doses, and/or formulations. Although the data with probiotics are still far too weak to convince clinicians, the concept is fascinating, and further studies would be more than welcome. Nanotechnology of probiotics is an area of emerging interest and opens up whole new possibilities for the probiotics applications. Their applications to the agriculture and food sector are relatively recent compared with their use in drug delivery and pharmaceuticals. The basic of probiotic nanotechnology applications is currently in the development of nano-encapsulated probiotics