The purpose of this research study is to determine whether a functional fiber, galactooligosaccharide, can help maintain immune strength and digestive health in free-living older adults. It is hypothesized that older adults consuming the fiber daily for 24 weeks over cold and flu season will have more healthy days due to a proliferation of beneficial bacteria within the colon which alters cytokine production and enhances natural killer cell function. Immune and gastrointestinal health will be evaluated via daily questionnaires obtained from 80 participants and from the collection of blood and fecal samples.

A prospective, randomized, parallel, double-blind, placebo controlled trial will be used. Healthy older adults will be recruited from the Gainesville area via direct mailing, flyers, list servs, presentations to clubs/organizations/church groups, social networks, etc. Informed consent will be obtained and once the informed consent is signed the inclusion/exclusion form will be reviewed to determine whether a subject qualifies for the study.

Prior to randomization, height, weight, age, and a stool sample will be obtained. On the day of randomization, blood will be drawn and saliva will be collected for baseline immune function studies from all subjects who qualify based on the final criteria (i.e., cannot have a cold on the day of randomization).

Subjects will be stratified based on body mass index and age and randomized via sealed envelope to the treatment (5 g GOS) or placebo groups (n=40/group). The fiber will be provided in small packets containing 2.5 g of fiber and 2.5 g sucrose (treatment) or 5 g of sucrose (placebo). Subjects will be instructed to add the contents of the packet to coffee, tea, water, milk, or other non-carbonated drink, hot cereal or pudding and mix well. Subjects will be told to consume two packets per day and maintain a daily study log. The daily questionnaire will ask about intake of the fiber, cold symptoms, and general health (i.e., new medications, doctor visits).

Between weeks two and three of the intervention, a second stool sample will be obtained. After three weeks of the intervention, subjects will receive the influenza vaccination and blood and saliva will be collected for immune function studies. Two weeks postvaccination (i.e., 5 weeks of intervention), blood and saliva will be collected for immune function studies. Subjects will continue the intervention and maintain daily logs for a total of 24 weeks. Subjects will also be asked to complete a questionnaire on a monthly basis regarding gastrointestinal symptoms and typical level of exercise.

Inclusion Criteria:

• 60 years of age or older
• willing to complete daily and monthly questionnaires
• willing to receive the fall influenza vaccination as part of the study protocol
• willing to provide 3 blood samples, 3 saliva samples, and 2 stool samples and answer a food frequency questionnaire over the course of the study
• willing to discontinue any immune-enhancing dietary supplements ( e.g., prebiotics and fiber supplements, probiotics, echinacea, fish oil, vitamin E >100% of the RDA or >15 mg/day)
• willing to take the study fiber for 24 weeks
• willing to provide a social security number to receive study payment Note: the subject can still participate if unwilling to provide SS#, but no financial reimbursement can be provided.
• had a cold in the last 12 months
• able to take foods and the study fiber without the aid of another person.
• eligible and willing to receive the influenza vaccine for the current year. That is, you cannot have already received an influenza vaccine for the 2010/2011 season prior to receiving it from the study

Exclusion Criteria:

• current smoker
• chronic allergies involving the upper respiratory tract (Chronic = taking allergy medicine daily)
• taking any medication for constipation or diarrhea
• currently taking any anti-inflammatory drugs on a regular basis
• currently treated for Alzheimer's disease
• allergy to milk or a serious allergy to eggs (note lactose intolerance should not be a problem because 1 fiber packet contains only 0.3 g of lactose whereas 1 cup of milk contains 12.8 g of lactose)
• currently being treated for any known illnesses or conditions that may impact perceived health such as HIV/AIDS, immune modulating diseases (autoimmune, hepatitis, cancer, etc.), diabetes, kidney disease, gastrointestinal diseases (gastric ulcers, Crohn's, ulcerative colitis, etc.)
• received chemotherapy or other immune suppressing therapy within the last year
• received antibiotic therapy in the past two months
• receiving supplemental oxygen