32 recreational athletes who will attend to the Grand Marathon in the nort west of Mexico, event that will be held on December 2, 2018 or 21k Trail to be held in April 2019 will be invited to the study. Participants will be informed about the study procedures through a consent informed. Participants will be randomly divided into two groups, 16 in the intervention group and 16 in the comparison group. The participants will be recreational athletes between 18 and 60 years old. They must have athletic experience of at least 3 years. The participants considered will be those who perform vigorous physical activity per week according to the criteria of the short version IPAQ instrument. Smoking subjects with food intolerances and allergies, cardiovascular history will be excluded. Patients who have had a respiratory infection symptom in the last two weeks will not be able to participate in the study. Participants who are consuming some type of food supplement will be excluded.

Two 18 ml of blood samples will be taken from the vein of the forearm by venipuncture of each participant, using K2EDTA tubes after and before supplementation period. Blood samples were taken before a corporal, aerobic and nutritional evaluations.

CB supplementation will begin 4 weeks prior to competition events. One group will consume 20 g of bovine colostrum daily in solution with water. The second group will consume a placebo product with a nutritional composition similar to the group with the treatment of bovine colostrum. Both groups should take the supplement before breakfast with empty stomach.

It is widely accepted that exercise provide important health benefits. However, vigorous or extenuate exercise can affect the correct function of the immune system. Athletes who perform extreme physical routines to improve their athletic performance can develop opportunistic infections. After 3 to 72 h of physical activity there is a phase called "open window for infection", which predispose to upper track respiratory infection (UTRI). URTI is the main cause of medical consultation in athletes with vigorous exercise practices.

Neutrophils are one of the most abundant leucocytes in blood; their phagocytic activity is essential to control bacterial infections. Recently, the interest in knowing the participation of these cells in the sport field is growing. Neutrophilia refers to a high concentration of neutrophils in blood, and this is a common condition after exercise. The controversial part is that vigorous exercise could limit some important functions, such as oxidative burst, degranulation and phagocytosis until 6 h after exercise. However, there are contradictory results in this topic.

To alleviate those immunological alterations in athletes, a nutritional intervention should be included. Bovine colostrum has been evaluated as a supplement due to its potential immunomodulatory properties. It improves immunological parameters in individuals who achieve prolonged exercise sessions, allowing URTI reduction. Bovine colostrum is a yellow aqueous compound secreted by cow mammary glands the first 72 h after partum. Bovine colostrum contains anti-microbial peptides, enzymes, immunoglobulins, cytokines, microRNA and growth factors, which are able to modulate the immune system, at local (intestinal) and systemic level. Due to these characteristics, bovine colostrum has been used to improve the immune response under different physiological conditions.

A study showed that bovine colostrum supplementation induces a CD89 expression pre-exercise, after 5 weeks supplementation with 10 g of bovine colostrum. This result is important, since CD89 is a membrane receptor in neutrophils that recognize antibody/antigen complexes to prime phagocytosis and degranulation. In other study, 3 weeks of bovine colostrum supplementation improved neutrophil degranulation 1 h post-exercise in athletes, after 2 h of physical exercise. Authors evaluated neutrophil oxidative burst post-exercise after bovine colostrum supplementation, but no effects were observed. However, these authors found better oxidative burst after 4 weeks bovine colostrum supplementation. At this time, the effect of bovine colostrum in phagocytosis activity is unknown.

Concerning the effects of bovine colostrum supplementation in the URTI incidence, the results are contradictory. Although, others found no benefit in the incidence of URTI after a bovine colostrum supplementation, other studies showed promising results. A retrospective analysis conducted in 2003 showed a reduction of athletes with URTI in the bovine colostrum supplementation group. Likewise, another study reported less episodes and duration of infections in physically active subjects. Other studies described a tendency to decrease the incidence of URTI in swimmers and cyclists.

Study Design

A total of 28 athletes attending the "Hermosillo Grand Marathon" (December 2, 2018) and/or the "Hermosillo Half Marathon" (March 2019) will be part of this study. In this randomized clinical trial, study subjects will be randomly divided in two groups, 14 in the intervention group (bovine colostrum supplementation) and 14 in the comparison group (placebo supplementation). The participants will be recreational athletes between 18 and 60 years old. They must have athletic experience of at least 3 years and have to perform a vigorous physical activity per week according to the criteria of the short version IPAQ instrument. Smoking subjects, with food intolerances, allergies or cardiovascular history will not be included. Athletes with respiratory infection symptoms two weeks before beginning the supplementation won't be part of this protocol. Participants who are consuming some other type of food supplement will not be included. This protocol is currently under evaluation of the Ethics Committee of our institution. Participants will be informed about the study procedures and will sign an informed consent.

Bovine colostrum supplementation will begin 4 weeks prior to the competition event. The intervention group will consume 20 g of bovine colostrum, divided into two doses of 10 g/day. The first dose will be before breakfast and the second before lunch. The comparison group will consume a placebo product.

Two blood samples (24 ml of each one) will be taken from the vein of the forearm of each participant, using tubes with EDTA. The first sample will be taken before the competitive event after 10 min of a sitting rest. The second sample will be obtained immediately at the end of the test with 3 minutes of sitting rest.

Inclusion Criteria:

• at least 3 years of training experience
• training for a half marathon competition
• No smokers
• Taking any kind of food supplements
• No alimentary allergies

Exclusion Criteria:

• Injuries
• not follow experimental indications
• cardiovascular disease
• treatment intolerances