With advancing age many  biological changes take place in the physiology and behaviour pattern of human beings. If the health is good then healthy ageing  is possible. This can help in preventing many harmful diseases. Recently, a lot of awareness has come in the minds of elderly to keep themselves fit and young. Many anti aging products are available in the market. The most common are the probiotic products which take a prime position as they come under GRAS category. They improve the gut health and immune system. The mechanism of aging needs to be studied in a big way. Functional ability and intrinsic capacity are important for healthy aging. This comprises all types of mental and physical capacities which include the ability to walk, think, see, hear and remember. The intrinsic capacity includes the presence of diseases, injuries and age-related changes. Other major factors are the environment at home, society, relationships, health and the amount of support they take from others. However,  premature aging seems to be due to genetic makeup. Diet and microbiota present in the gut play an important  role in aging. With age changes take place in the microbiota of the gastrointestinal tract and dietary patterns. Decline in cognitive and immune functions are common. Probiotics are live microbes, which when administered in suitable amounts confer a health benefit to the host and are helpful in maintaining good health in   the elderly. The most common probiotic strains are  Lactobacillus spp. and Bifidobacterium spp. These have been studied by many scientists as these have the ability to produce enzymes, bacteriocins and γ-aminobutyric acid (GABA) which function as neurotransmitters. Probiotics can prevent  the growth of harmful microbes like Helicobacter pylori in the gut which cause ulcers. It is very important to educate elder people on the various aspects of health improvement especially the role of probiotics.

With age, there are changes in some genes, the body cells  get worn out with time and lose the ability to regenerate. Cross-linked proteins, DNA damages and excess of free radicals cause aging. During aging the cell division gets arrested as the telomeres become smaller in size, there are epigenetic changes, mitochondrial dysfunction, stem cell collapse, cellular senescence, loss or change in intercellular communication, loss of proteostasis and nutrient sensing gets deregulated. DNA methylation can also change the aging process. Scientists have found that an anti-inflammatory diet can be helpful for telomeres and can reduce the cardiovascular risk and mortality. These changes can be reversed with the use of probiotics ( Lactobacilli and Bifidobacteria). Probiotics have been found to be useful to decrease apoptosis in the colon. With age the absorption of carbohydrates, lipids, amino acids, minerals and vitamins get reduced to a large extent. In order to keep the digestive system in good condition it is important that the gut microflora has good number of probiotics along with the diet which contains prebiotics. Both innate as well as adaptive immune responses get affected with age. Microbial flora can also get  altered with the overuse of antibiotics. Looking into these problems it is advised that with age it is important that the small intestine has a large number of good microbiota ( Probiotics and prebiotics) which can be regulated with the diet. It has been found by the scientists that the supplementation of probiotics increases the number of natural killer cells along with  phagocytic activity and enhances immunity in elderly people. Consumption of probiotics have demonstrated increased levels of serum albumin and intestinal immunoglobulin A (IgA). When the prebiotics are supplemented along with the probiotics it stimulates the growth of probiotic cultures. Therefore, the  synbiotic administration helps in digestion and decreases many diseases. The prebiotics interact with the gut micro flora and produce a number of  short chain fatty acids (butyric and propionic) which inhibit the growth of colon tumour cells. Due to the physiological modifications there is a change in the nutritional needs of elderly persons(body composition, the gastrointestinal tract, water balance and bone health).Proteins are very important macronutrients for good health. All the 20 amino acids are not synthesised by the human body which have to be provided through food. Dietary protein affects multiple physiological mechanisms. Whey (contains probiotics and prebiotics) and casein from milk and beef proteins are rich in essential amino acids and are thus high-quality sources. It can enhance the secretion of insulin-like growth factor 1 (IGF-1) which usually goes down with progressing age. The protein diet helps in increasing the bone mineral density and helps in calcium metabolism and  improves hypertension and endothelial function of the arteries. With age many bacteria, multiply in the intestine due to hypochlorhydria, a deficiency of hydrochloric acid in the stomach. This allows the carbohydrates to ferment (in the colon)instead of being digested and absorbed in the jejunum resulting in flatulence, diarrhoea, constipation and abdominal cramps. It is well-recognized that a balanced diet has a beneficial impact on the immune system. Trace elements (selenium, zinc, iron) and vitamins (A, E, C) as well as polyunsaturated omega-3 fatty acids are vitally important. An adequate supply of these micronutrients can improve the oxidative balance. High life expectancy and low susceptibility to illness can be achieved with a balanced diet. The supplementation of fermented milk in a study suggested that H61 could be a potent probiotic for the suppression of age-related problems. Life-extending property of L. lactis strain, namely L. lactis subsp. lactis JCM 5805 have been proved. Also the dendritic cells get stimulated for better  nervous function. Supplementation of Lactococcus lactis subsp. lactis strains (SAMP1 and SAMP10) activated the IFN-α induction activity in SAMP1 and reduced the age related skin thinning, improved the T cell ratio, increased the expression of tight junction related genes and suppressed the expression of muscle degeneration gene. It was found that the probiotic supplementation reduced the skin wrinkles, dehydration and simultaneously there was an increase in the skin shine and elasticity. Probiotics are live microorganisms which when imparted in sufficient numbers give beneficial effect to the consumer. The most common probiotics include Lactobacillus rhamnosus GG, Lactobacillus reuteri, Bifidobacteria and certain strains of Lactobacillus casei / Lactobacillus acidophilus group. 

There are many probiotic products in the market which are commercially available. The table below gives the brand name, specific product, the functional bioactive peptide and the health claim.

Table-1.  Commercial dairy products and ingredients with health or function claims based on bioactive peptides

Brand name	Product	Functional bioactive peptide	Health/ Function claim
Calpis	Sour milk	Val-Pro-pro, Ile-pro-pro from casein and k-casein	Reduction blood pressure
Biozate	Hydrolysed whey protein isolate	β-lactoglobulin fragments	Reduction blood pressure
Product F200/ Lactium	Flavored milk,drink , confectionery, capsule	As 1- casein (91-100) ( Try-Leu-Gly-Tyr-Leu-Glu-Gln-Leu-Leu-Arg)	Reduction of stress effects
Capolac	Ingredient	Casein phosphor peptide	Helps mineral absorption

There are many probiotic products which can be prepared naturally. These have been described as below.

1. Cereal based probiotic fermented dairy beverages:   Addition of cereals into milk enriches the mineral value and fibre. Cereal solids are  incorporated into milk before and after fermentation. 
2. Fermentation of Sauerkraut :               Mixed culture fermentation on cabbage. 
3. Brined cucumbers:                              The fermentation is by homofermentative LAB. 
4. Probiotics in production of Soy sauce: Soysauce and sourdough both utilize the interaction between yeasts and Lactobacilli.
5. Sourdough bread:                                 Fermentation of bacteria and yeast to make bread. 

Probiotic Tempeh : A fermented soybean product covered with white mold, a compact cake produced by the fermentation of dehulled, hydrated, soaked and precooked soyabean cotyledons. The fermenting organism is Rhizopus oligosporus. These products are beneficial for health as they decrease the risk of heart diseases, strokes, osteoporosis, cancer, digestive disorders and reduction of fat. There are other cereals and legume substrates like chick pea, horse gram, lupin, common bean, ground nut, wheat and maize which are used for tempeh preparation. Soya milk has also been utilized for the production of tempeh. When fresh it is perishable due to the sporulation by fungi. However, if it is blanched, dried and powdered it can be stored for longer time. Tempeh is known to contain small amounts of oxalates which if accumulated can cause health problems. Fermentation of soybean improves digestibility by reduction of antinutritional factors like tannin and phytate in addition to production of acids which inhibit the production of pathogenic bacteria which is important in the manufacture of food. Recently, a synbiotic tarhana (Turkish fermented cereal food) was produced as a functional food from the fermentation of wheat flour, some spices (salt, pepper, dill, sweet marjoram and tomato). Another product with different concentrations of the probiotic culture containing Streptococcus thermophilus, Lactobacillus acidophilus and Bifidobacterium bifidum with pepper (Capsicum annum), onion, yoghurt and prebiotic (inulin and lactose each 3%) was found good for elderly. A symbiotic shake has been developed and manufactured by the company Maxinutri Alimentos LTDA using specific formulation containing 4.5% fructooligosaccharide (Corns Products),  2% Lactobacillus acidophilus (Fortitech), 2% Bifidobacterium bifidum (Fortitech). Thus, cereal based feeds are amended with additional protein sources to attain the required protein levels. Functional foods provide a health benefit beyond the traditional nutrients they contain. Probiotic microorganisms contribute to confer the functional properties. Soymilk, the water extract of soybeans (Glycine max) is a rich source of protein, iron, calcium and unsaturated fatty acids as well as free of lactose that serve as a substitute for dairy milk, the  lactose-intolerant consumers and milk-allergy patients can also consume this product. Fermentation of soymilk with probiotic microorganisms as lactic acid bacteria (LAB) and Bifidobacteria have been found to improve the bioavailability of isoflavones, with higher digestibility of protein and more soluble calcium. It enhances intestinal health, and supports immune system. Soy-based foods are hypolipidemic, anticholesterolemic, antiallergic and antiatherogenic. They also reduce the protein malnutrition problems ultimately improving the health of the elderly. It is also very vital that the elderly eat a balanced diet, have healthy interaction and have physical exercises. They need to improve their knowledge bank with continuous reading on health foods, health promotion and healthy ageing.