The preventive effect of RIBEX against the common cold syndrome was examined on elderly people. RIBEX, containing arabinoxylan derivatives Hydrolysis Rice Bran (HRB) (also known as Lentin Plus 1000), was prepared from the water soluble dietary fiber fraction from rice bran through partial processing by carbohydrate complex of Lentinus Edodes mycelia (shiitake).

Using the non-chemical and non-biological treated water soluble fraction of Rice Bran (RB) as control, the examination was conducted by the cross-over double blind manner through the administration term of 6 weeks for each material. Fifty elderly people who stayed in a care institution under Japan`s Long-term Care Insurance participated in this study. The results of thirty-six participants who showed comparative data in both terms were analyzed stastistically. The most popular reason for withdrawal from the study was "leaving from the institution by a care contact". There was no withdrawal due to the side effects of test foods. We observed symptoms such as "cough", "fatigue", "fever", "sore throat", "sputum", "nasal signs", and "sore breast", and calculated them, based on the juggements of the medical staff.

Although thirteen participants (36.1%) experienced at least one symptom in the both terms, the total scores were significantly high value (p<0.05) in the term of R.B. The average duration in which the participants experienced symptoms was 2.6 days in the term of RB whereas 1.2 days in that of HRB, which was not statistically significant. While there are many reports that HRB increases NK cell activity, no significant data was observed in this study because the participants had enough NK cell acitivites from the start.

HRB shortened the duration of the symptoms, reduced the worse and the necessity of symptomatic therapy, and was useful for the reduction of physical burden of acute respiratory tract infection.