Impact of EPA and DHA Supplementation on Plasma Biomarkers of Inflammation (n3)

The proposed study will be undertaken according to a double-blind randomized placebo controlled cross-over design with 3 treatment phases: 1- high DHA, 2- High EPA, 3- Control. Each treatment phase will last 10 weeks and will be separated by 8-week washouts. Participants will be randomized to one of 6 treatment sequences while stratifying for sex. Treatments will provide 3 identical 1g capsules per day. During the 3 treatment periods, subjects will receive in random order 0g/d EPA+DHA (3g corn oil placebo), 3g/d EPA (>90% EPA), and 3g/d DHA (>90% DHA). Long chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) will be provided in their re-esterified triacylglycerol form as studies have shown that bioavailability was greater when EPA and DHA were consumed as TG rather than as ethyl esters. The therapeutic dose that maximizes the anti-inflammatory effects of LCn-3PUFA in patients with inflammation has not been established, although data suggest that they may be dose-dependent. However, studies in healthy human volunteers suggest that an intake > 2 g EPA + DHA/day is required to affect inflammatory processes. Many of the available studies have used a dose of EPA+DHA that was lower than 2g/d, with no apparent anti-inflammatory effects. A study has shown that a dose of 1.8g/d of EPA+DHA induced significant changes in peripheral blood cell (PBC) inflammation gene expression, with no change in plasma CRP concentrations. In the present study, we propose to use a dose of 3 g/d for each individual LCn-3PUFA tested, which is at the higher end of the recommended intake for patients with high plasma TG, but which will maximize our chance to observe changes in inflammatory markers and to differentiate the effects of EPA and DHA, if they exist. Participants will be instructed to maintain a constant body weight during the course of the study. They will also be counselled on how to exclude fatty fish meals (including salmon, tuna, mackerel, and herring), fish-oil supplements, flax products, walnuts, and omega-3-enriched eggs during the study. Vitamin supplements and natural health products will be strictly forbidden during the entire experimental period, with the exception of calcium and vitamin D, which will be allowed at a stable dose. Although alcohol consumption will be permitted during the study with intakes not exceeding one serving (12-15 g alcohol) per day, it will be forbidden for the 4 days that precede the various tests at the end of each treatment phase. Subjects will also be instructed to maintain their usual physical activity except for the 4 days that precede blood sampling at the various stages of the study, during which they will be asked to remain sedentary.

Inclusion criteria

• Men and women aged between 18 and 70 years with abdominal obesity as defined by the International Diabetes Federation criteria and a measure of plasma CRP >1 mg/L
• Stable body weight for at least 3 months prior to randomization.
• Pre-menopausal women with regular menstrual cycle (25-35 days)

Exclusion criteria

• Plasma CRP > 10 mg/L at screening
• Extreme dyslipidemias such as familial hypercholesterolemia
• Previous history of cardiovascular disease (coronary heart disease, cerebrovascular disease or peripheral arterial disease)
• Subjects taking medications known to affect inflammation (e.g. steroids, binging alcohol)
• Subjects taking LCn-3PUFA supplements within 2 months of study onset.