The purpose of this study is to determine whether the consumption of a nutritional supplement with micronutrients and herbal extracts has an effect on the incidence of acute respiratory infections in susceptible adults.

Our hypothesis is that subjects who consume the nutritional supplement will have a lower incidence and duration of acute respiratory infections in comparison with the placebo group.

We conducted a randomized, parallel, double-blind, placebo-controlled, 90-day clinical trial from January to April, 2012. All staff who worked at the Omnilife's Entrepreneur Support Department (CREO by its initials in Spanish) were invited to participate. This department within Omnilife has a high incidence of acute respiratory infections (ARI) as reported internally by the company's medical service (accounting for 55% of doctor visits within the department in 2010) and hence, they represent a high number of individuals susceptible to ARI.

We held a preliminary session with the department's entire staff to explain the procedures; we asked subjects interested to participate in the study to sign an informed consent form and fill a clinical history. The latter included an assessment of stress, using the Perceived Stress Scale (in which higher scores indicate higher levels of stress), and physical activity, using the International Physical Activity Questionnaire or IPAQ (in which physical activity is categorized in three levels: light, moderate and vigorous).

In a second session the same week, participants visited the company's medical service for measurements of their weight and height (in accordance with the International Society for the Advancement of Kinanthropometry or ISAK standards), control laboratory tests and a medical examination to rule out the presence of infections. Weight measurements were taken using a Tanita BC553 Ironman Inner Scan Body Fat Scale (capacity of 150 kg, accuracy to 0.1 kg). Height measurements were made using a Seca 206 Stadiometer (accuracy to 0.1 cm, measuring range to 220 cm). Both measurements were performed by a two certified and standardized anthropometrists. Body mass index (BMI) was subsequently calculated using both variables as follows: BMI = weight in kg/(height in m)2.

The medical examination was performed by the attending physician and a nurse. It consisted of an assessment of vital signs following procedures described in the literature and a physical examination of bodily organs and systems. Temperature was measured using a Microlife MT 1931 digital thermometer (measuring range from 32 to 43.9°C, accuracy to 0.1°C). Heart and respiratory rates were measured using a 3M Littmann Classic II S.E. stethoscope. Blood pressure readings were taken using a 3M Littmann Classic II S.E. stethoscope and an Aneroid Sphygmomanometer ce0483 (18-300 mmHg measurement range, accuracy to 2 mmHg).

Laboratory tests were conducted with the support of an external laboratory (Instituto Diagnostico Especializado Arboledas, IDEA by its initials in Spanish). Included were a blood test of six items (fasting glucose, uric acid, creatinine, blood urea nitrogen, cholesterol and triglycerides) analyzed by the spectrophotometric method, a complete blood count with a flow cytometry/microscopy analysis of platelets, and a spectroscopy analysis to assess liver function. Subjects of laboratory analyses were tested after a 12-hour fast. This laboratory has obtained quality control certification from the Quality Assurance for Laboratories Program (PACAL) and the Internal Evaluation Quality Program (PREVECAL). In addition, its staff is certified in clinical diagnosis by the National Association of Clinical Chemists (CONAQUIC).

Subjects who met inclusion criteria were randomly assigned to two groups: one which received the supplement (n=30), and a control group who received a placebo, which consisted in a mixture of maltodextrins, colors and flavors. Every day two dietitians prepared the products, who then gave the prepared products to two different supervisors who in turn gave the product to each participant for consumption. The supervisors recorded product administration and consumption for each participant on a control form.

Simultaneously, each week the supervisors provided each participant with an ARI symptom and side effect diary to be filled in daily (indicating whether or not the symptom in question had presented). Participants delivered the supervisors their filled-in diaries the following week. Subjects were also requested not to self-medicate in the event they should feel any of the symptoms and to notify the principal researcher and attending physician, who would make a clinical assessment to confirm the presence or absence of ARI and provide any needed medical treatment. In such cases, participants were not to be excluded from the study, but treatment provided to them was documented. At the end of the supplementation period, the initial assessments were performed again. Subjects were also asked about their perceptions of their own health at that time compared to how they felt at the beginning of the study.

Quantitative variables are expressed as mean (SD). Qualitative variables are expressed as frequency (%). Fisher's exact test was used to compare distribution percentages of qualitative variables between groups and to compare the total proportion of ill subjects across intervention groups using intent-to-treat and per-population concepts. The risk ratio and the risk difference were also calculated for episodes of ARI. To compare the average of quantitative variables between treatments, the Mann-Whitney U test was used. Statistical analyzes were run using the SPSS program version 10 for Windows and Open Epi version 3.01; p<0.05 was considered as significant.

Inclusion Criteria:

• Healthy adult subjects (without active respiratory infections, or without diseases that compromise immune system)
• Who presented no abnormalities in their laboratory tests (active infections, immunosuppression, renal or hepatic impairment)
• Who did not take drugs that affect the immune system (anti-inflammatory drugs, antibiotics, steroids).

Exclusion Criteria:

• Subjects with active acute respiratory infections.
• Subjects with chronic respiratory disease requiring treatment other than bronchodilators at the time of assessment.
• Subjects with diseases affecting the immune system (autoimmune illness, diabetes, etc.)
• Pregnant women or currently nursing.
• Subjects with cardiovascular disorders (uncontrolled hypertension) or neurological disorders (epilepsy).
• Subjects with allergies to any components of the products.
• Subjects with low treatment adherence (less than 80%).