The aim of the study is to estimate the effect size of a 5-week consumption period of different dietary non-digestible polysaccharides (NPS) on antibody response to influenza vaccination and cellular immunity of healthy volunteers (aged ≥ 50) for clarifying whether these NPS may enable enhancement of immune defence and to estimate the sample size for a confirmative trial. Furthermore the effects on faecal microbiota and its metabolites will be investigated.

The study is conducted in the frame of the collaborative project 'FibeBiotics' (Nr. 289517) (Fibers as support of the Gut and Immune function of Elderly - From polysaccharide compound to health claim) within the Seventh Framework Programme (FP7) for Research and Technological Development of the European Union (EU).

Inclusion Criteria:

• Free-living postmenopausal woman and men aged ≥ 50 years willing to have influenza vaccination season 2012/2013
• willingness to abstain as far as possible from food and supplements containing probiotics, prebiotic supplements, other fermented products, supplements containing vitamins and minerals as well as willing to sustain on a low dietary fibre diet for 7 weeks.
• written informed consent

Exclusion Criteria:

• Subjects enrolled in another clinical study in the last 4 weeks
• Subjects already vaccinated against influenza during 2012-2013 with either the influenza vaccine used in the present study or another influenza vaccine
• vaccination against influenza within the previous 10 months
• suffering from influenza or influenza-like illness within the previous 10 months
• other vaccinations during and within 2 months before the study
• symptoms of common infectious diseases (CID) of the airways or other organ systems e.g. gastrointestinal tract in the last 4 weeks before inclusion
• known congenital, acquired or iatrogenic immunodeficiency (e.g. HIV, chemotherapy, immunosuppression)
• active autoimmune diseases
• allergy or hypersensitivity to any component of the vaccine (e. g. chicken egg protein, certain antibiotics)(s. a. 9.2)
• allergy or hypersensitivity to any component of the test product (e. g. yeast, gluten, shiitake mushrooms)
• allergy to latex
• known coeliac disease (gluten enteropathy)
• bowel movement less than 3 times per week
• subjects, who meet 2 or more Rome III criteria for constipation or who take laxatives on a regular basis
• severe chronic disease (cancer, IBD, malabsorption, malnutrition, chronic inflammatory diseases, renal, hepatic or cardiac diseases, COPD, respiratory insufficiency)
• chronic abdominal pain
• malformation of fingers
• systemic treatment or topical treatment likely to interfere with evaluation of the study parameters: antibiotics, intestinal or respiratory antiseptics, anti-rheumatics, antiphlogistics (except aspirin or equivalent products preventing from aggregation of platelets or blood clotting) and steroids prescribed in chronic inflammatory diseases
• other treatments likely to interfere with study outcome (e.g. laxatives, body weight management and/or medication)
• treatments with calcium antagonists and nitrates and alpha blockers
• diabetes mellitus on drug therapy
• severe neurological, cognitive or psychiatric diseases
• surgery or intervention requiring general anaesthesia within 2 months before the study
• vegetarian, vegan
• eating disorders (e.g. anorexia, bulimia)
• alcohol and drug abuse
• pregnancy or lactation
• legal incapacity
• blood parameters: Hb < 12 g/dL Liver transaminases (ALT, AST) > 2-fold increased Serum creatinine > 1,2 mg/dL