Factors influencing proportion and composition of CLA in beef.

Bovine meat is criticised for the bad nutritional image of its lipids and fatty acids. However, with dairy products, beef is the major source of conjugated linoleic acid (CLA) which could have several human health benefits. The present study compared, from data of five nutritional experiments on bovine animals performed by the laboratory, the impact of factors linked to the animals (breed, age, sex, type of muscle) and to feeding conditions (basal diet, lipid supplements) on the CLA proportion and composition in muscles. Among these factors, linseed supplementation was an efficient way to increase CLA proportion in beef (+22% to +36%) but was highly modulated by the nature of the basal diet, and by intrinsic factors (breed, age/sex, type of muscle) since these ones could modulate CLA proportion in beef from 24% to 47%. Moreover, these factors modified also the proportion of cis,trans-CLA, related to cis,cis- and trans,trans-isomers. Specific biological properties of these latter isomers should be determine to understand the consequences of intramuscular CLA isomer variations for the health of consumers.

Antioxidant status and oxidative stress in professional rugby players: evolution throughout a season.

Physical training is known to increase the antioxidant defence system and reduce exercise-induced oxidative stress. However, intense physical aerobic and anaerobic training and competition such as those imposed on professional rugby players, can induce an increase of oxidative stress which can be implicated with the arrival of overtraining. The aim of this study was to test the effect of training and competition load on oxidative stress, antioxidant status, haematological, and cell damage markers in high-level rugby players during a competitive season. Blood samples were collected four times in one year. Oxidative stress (Rmax), antioxidant (vitamin E, uric acid, TAC, and lag phase), haematological (neutrophils and monocytes) and biochemical (CK and myoglobin) parameters, as well as training and competition load, and competition results were measured. Intense periods of training and competition (T1 and T4) induced a significant higher maximum rate of conjugated dienes oxidation (+67.2% in T1 and +40.6% in T4) compared to those observed at the reference time (T3). Those periods also induced an increase in uric acid (+6.9% and 3.2%), and inflammatory markers such as monocytes (+13.3% and 10.7%). On the other hand, vitamin E (-8.7% in T1) and lag phase (-23.0% and -14.7%) were lower during these periods showing a possible training-induced antioxidant down-regulation. The less intense period of training (T2) was accompanied by lower neutrophils (-8.5%), CK (-53.7%), and myoglobin (-16.2%) values. The results suggest that oxidative stress and antioxidant measurement are significant in the biological follow-up of athletes.

Competition and food restriction effects on oxidative stress in judo.

We examined the effects of weight loss induced by restricting energy and fluid intake on antioxidant status and oxidative stress of judo athletes. Twenty male judoka were randomly assigned to one of two groups (Group A: called diet, n = 10; height 174.8 +/- 1.9 cm, body weight 75.9 +/- 3.1 kg; they were asked to lose approximately 5 % of their body weight through self-determined means during the week before the competition; Group B: called control, n = 10; height 176.4 +/- 1.1 cm, body weight 73.3 +/- 6.3 kg maintained their body weight during the week before the competition). A battery of tests was performed during a baseline period (T1) on the morning of a simulated competition (T2) and 10 minutes after the end of the competition (T3). These tests included assessment for body composition, determination of lag phase (Lp) before free radical induced oxidation, maximum rate of oxidation (Rmax) during the propagating chain reaction and maximum amount of conjugated dienes (CDmax) accumulated after the propagation phase, and lipidic profile. Uric acid concentrations were also evaluated in plasma. Dietary data were collected using a 7-day diet record. We noted that the athletes followed a low carbohydrate diet whatever the period of the investigation. Concerning antioxidant nutrients, we can notice that mean nutritional intakes are in the normal range values for vitamin A, C and E at T1 and T2. Rapid weight loss induced a significant increase in Lp values (p < 0.05) and uric acid concentrations without alterations in oxidative stress. Our data also showed that the competition induced the same changes of oxidative-antioxidant status whatever the dietary intake during the seven days before the competition. Moreover, the effect of the competition on the antioxidant and oxidant parameters was more pronounced than the diet. Theses results could be linked to the food containing a large proportion of PUFA and a relative low proportion of carbohydrates.

Effects of dietary n-6 or n-3 polyunsaturated fatty acids protected or not against ruminal hydrogenation on plasma lipids and their susceptibility to peroxidation in fattening steers.

Two experiments were conducted using crossbred Salers x Charolais fattening steers fed diets enriched with no supplemental oilseeds or oils rich in either n-6 PUFA (from sunflower seeds) or n-3 PUFA (from linseeds) provided either as seeds incorporated in the diet (i.e., not protected from ruminal bacterial hydrogenation) or by chronic infusion into the duodenum (protected form). In the Sunflower experiment, animals (initial age = 454 +/- 20 d; initial BW = 528 +/- 36 kg) received a control diet for 70 d (CS, n = six) consisting of hay and concentrate, or the same basal diet supplemented with sunflower oil (4% of dietary DM), either fed as seeds (SS, n = six) or infused into the duodenum (ISO, n = six). The same experimental design was applied to animals (initial age = 412 +/- 33 d; initial BW = 536 +/- 33 kg) used in the Linseed experiment (CL, LS, and ILO; n = 8 per group). For all animals, blood was sampled every 15 d during 70 d. In both trials, a significant diet x time interaction (P < 0.001) was detected for plasma concentrations of apolipoprotein A-I, phospholipids, and free and esterified cholesterol, with values increasing with time during administration of the PUFA-rich diets being more evident with ISO and ILO diets. Plasma fatty acids were altered with oil infusions, with increased concentrations of n-6 (1.6-fold; P < 0.05) and n-3 PUFA (4.5-fold; P < 0.05) and of their respective indicies of peroxidizability (1.2- and 1.5-fold with Diets ISO and ILO, respectively; P < 0.05). In vitro copper-induced peroxidation of lipids revealed a decreased length of the lag phase in the process of conjugated diene generation by 48% (P < 0.005) with the ILO diet, indicating less resistance against peroxidation than in control steers. Compared with CS, the ISO treatment increased plasma alpha-tocopherol (x2.5; P < 0.05) leading to similar resistance against peroxidation. After depletion of this vitamin, the rates of peroxidation and production of conjugated dienes were greater (twofold; P < 0.05) with the ISO and ILO diets than with the others. In conclusion, infusion of sunflower or linseed oil into the duodenum altered the composition and distribution of plasma lipids and increased the plasma concentration of PUFA. The sensitivity of plasma PUFA to peroxidation depends on the plasma level of antioxidants, especially vitamin E, a nutrient important both for the health of animals and for the stability of the blood lipids until their tissue deposit.