Chronic inflammation has been linked to many diseases including cardiovascular disease, stroke, diabetes mellitus and cancer (Pischon et al., 2011). Epidemiologic studies have demonstrated that populations that consume more fish and less red meat have lower incidences of some inflammatory diseases such as gastric cancer and cardiovascular disease (Huang et al., 2011; InterAct Consortium, 2011). The two most important omega-3 (n-3) polyunsaturated fatty acids are eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) and it has been suggested that diets high in these fatty acids may benefit mood, behavior and physical performance (Krumbholz et al., 2010; Mozaffarain et al., 2011; Oddy et al., 2011; Poudyal et al., 2011).
It has also been demonstrated that increased consumption of omega-3 fatty acids improves lipid profiles, reduces oxidative stress and reduces inflammation via inhibition of pro-inflammatory mediators such as leukotrienes, prostaglandins and cytokines (Gopinath et al., 2011; Huang et al., 2011). Another manifestation of inflammation is muscle soreness that can occur in both elite athletes and normal human adults. Muscle soreness, sometimes called delayed onset muscle soreness (DOMS), is characterized as a type of soreness that is usually caused by a new or unaccustomed exercise. The exercises that most frequently cause DOMS are primarily exercises of eccentric muscle action i.e.: where a muscle generates tension to control the rate at which it lengthens (Balnave and Thomson 1993; Bobbert et al., 1986; Wessel and Wan 1994). The onset of DOMS generally occurs within 24-48 hours following exercise, may be associated with swelling, tenderness and discomfort, and may be experienced up to 1 week following heavy exercise (Bobbert et al., 1986; Wessel and Wan, 1994). While the physiology of DOMS is not completely understood, DOMS is likely related to damage of sarcomeres, ensuing swelling of damaged muscle fibers and subsequent initiation of an inflammatory response (Herbert et al., 2011; Lieber and Friden, 2002; Proske and Morgan, 2001). Strategies that have been tested for their potential to alleviate DOMS include massage therapy, stretching, ultrasound, pharmacologic anti-inflammatory drugs and dietary supplements including omega-3 dietary supplements (Herbert et al., 2011; Hyldahl et al., 2010; Lieber and Friden, 2002; Proske and Morgan, 2001; Rhea et al., 2009). The hypotheses that omega-3 dietary supplementation may reduce DOMS posits that higher systemic omega-3 levels correlate to increased omega-3 concentration in the muscle cell wall thereby increasing elasticity and flexibility and reducing the risk of muscle cell injury during heavy exercise. It has been shown that the omega-3 fatty acid content in omega-3 dietary supplements can increase omega-3 index levels and attenuate inflammatory pathways such as the cyclooxygenase and lipoxygenase pathways resulting in a decreased inflammatory response and reduced pain (Krumbholz et al., 2010; Poudyal et al., 2011). Systemic omega 3-levels are commonly calculated as an omega-3 index (N3 Index). The 0-12 range of the N3 Index expresses the amount of EPA and DHA (in weight [%]) present in the tissue cell membrane lipid fraction (Von Schacky, 2010). The Omega-3 Index has been previously characterized as an important risk factor for coronary heart disease (Harris and von Schacky, 2004). Subjects with an N3 Index less than or equal to 4.0 (low N3 index) are considered to have higher cardiovascular risk. Subjects with an N3 index between 4 and 8 are characterized as medium risk, while subjects with an N3 Index of 8 are considered low risk for suffering a fatal cardiovascular event (Harris and Von Schacky, 2004; Von Schacky, 2010).
The purpose of the study was to test whether subjects with a higher N3 Index displayed differences in the incidence of DOMS, inflammatory biomarkers and quality of life following vigorous exercise.
Men and women over the age of 18 were allowed to participate in the study if they were otherwise healthy, did not currently take any dietary supplements containing fish oil or omega-3 and were able to read and sign the informed consent in the English language. Excluded from the study were subjects with any known medical conditions, any current medication use for cardiovascular disease including hypertension, hyperlipidemia or past medical history of any coronary disease, current treatment for diabetes mellitus, recent physical injury, excessive consumption of fish (defined as consumption 1 time per week, current drug or alcohol addiction and any reason in the opinion of the investigator not to take part in the study.
This was an Institutional Review Board (IRB) approved study (Ithaca College Institutional Review Board) in 69 human volunteers. Study subjects were randomized 2:1 to take either 6 capsules of an omega-3 dietary supplement per day (KD Pharma, Bexbach, Germany, 2.7g) or 6 capsules of a placebo agent (high oleic sunflower oil) with food 30 days prior to exercise (baseline (0 hour)). Group 1 was subjects who had taken the supplement with an Omega-3 Index above 4.0 (high N3 Index) and Group 2 was subjects who had taken the placebo supplement and had an Omega-3 Index less than 4.0 (low N3 Index). Participants in group 1 who had received omega-3 supplementation of 2.7g EPA+DHA per day for 30 days moved from an initial mean N3 Index of 3.6 [+ or -] 1.66 to 5.4 [+ or -] 1.05 (p = 0.0001) as measured at day 0 of the exercise portion of the intervention, indicating good bioavailability of the omega-3 supplement. A second subgroup receiving high oleic acid placebo capsules had an initial mean N3 Index of 3.75 [+ or -] 0.95 and after 30 days of placebo supplementation, on day 0 of exercise, a mean value of 3.94 [+ or -] 1.08.
Blood draw was performed at 0, 24-, 48-, 72-, and 96 hours post-exercise for measurement of plasma Creactive protein (CRP) (mg x [ml.sup.-1]) and creatine kinase (CK) (IU x [L.sup.-1]) by the following procedure. Three milliliters of blood was drawn from the antecubital vein of the non-exercising arm. Blood was collected in a serum separator tube, allowed to sit for 20-60...