The Nutrition Examination Research Digest (NERD) aims to provide rigorous, unbiased analysis of the latest and most important nutrition and supplementation studies. Click here to subscribe or login if already a subscriber .
Study under review: Effects of dietary saturated and n-6 polyunsaturated fatty acids on the incorporation of long-chain n-3 polyunsaturated fatty acids into blood lipids
Introduction
The Examine.com page on fish oil cites 735 unique references, which speaks to the vast array of research investigating health effects of the two primary marine-based omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Much of fish oil’s health effects come from its incorporation into cell membranes, where it is used during times of stress to help reduce inflammation. The cellular membrane ratio of omega-3 to omega-6 fatty acids is important because the stress response will use either one without discrimination, and the omega-6 fatty acids are more likely to promote inflammation.
The standard Western diet has a very high omega-6 to omega-3 ratio (15:1), which is associated[1] with many inflammatory conditions including cardiovascular disease, cancer, and autoimmune diseases. By supplementing fish oil, the omega-6 to omega-3 ratio is reduced, which can reduce inflammation and hence lower susceptibility to various chronic diseases common among industrialized societies.
Omega-3 and omega-6 fatty acids do not just compete at the cell membrane level, however, as they also share a class of enzymes that are responsible for their bioconversion. For instance, both alpha-linolenic acid (ALA, a type of omega-3) and linoleic acid (a type of omega-6) compete for desaturase enzymes (as shown in Figure 1) that are responsible for converting them into EPA and arachidonic acid, respectively.
It is possible that supplementing fish oil containing preformed EPA and DHA may circumvent the problem of competition for these enzymes. However, it has been demonstrated[2] in rats that feeding fish oil in combination with saturated fatty acids (SFAs) increases the incorporation of EPA and DHA in cell membranes to a greater extent than feeding fish oil in combination with omega-6 fatty acids. Thus, it is important to understand how the background diet may influence the effect of fish oil supplementation in humans.
The study under review aimed to compare the degree of EPA and DHA incorporation into cell membranes and the effects on blood lipids in humans consuming a SFA-enriched diet or an omega-6-enriched diet.
The benefits of fish oil may come in part through balancing the body’s ratio of omega-3 to omega-6 fatty acids, which has downstream anti-inflammatory effects. Human studies have not yet investigated how fat composition in the background diet may influence the effect of fish oil supplementation. The current study aimed to fill this knowledge gap.
Who and what was studied?
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Other Articles in Issue #16 (February 2016)
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Dieting, with a side of extra protein
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Promoting ‘high quality’ weight loss: protein and weights
By Stuart Phillips, PhD
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Vitamin E bioavailability isn’t always the same
The vast majority of people don’t meet the recommended intake level for vitamin E. And it turns out that certain people may not absorb vitamin E as well as others, and they might actually be the ones who need it most.
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Spice up your satiety?
The active ingredient in spicy food, capsaicin, seems to have some effect on satiety. But researchers weren’t quite sure what it was or how it happens, until this highly controlled experiment was done
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Little bugs for big depression
Your gut and your brain communicate much more often than you’d think. In fact, all the time. Hence the potential for consuming gut inhabitants (aka probiotics) and impacting brain-related maladies
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The Tyranny of the Outlier: Focusing on the best of the best sometimes diminishes the rest of us
By Lou Schuler
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Have a nice trip, see you next fall
Some preliminary evidence has pointed to a potentially greater risk of falls for elderly people taking vitamin D. That’s put to the test in this year-long randomized trial.
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A vitamin D-efense against multiple sclerosis
MS involves a complex interplay between the nervous and immune systems (and potentially others as well). This is the first trial looking at the safety and immune impact of vitamin D supplementation for MS patients.
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The newest index on the block… the hydration index!
Hydration has become more of a marketing term than a scientifically accurate one. These researchers created an index to specifically measure the hydration impact of different beverages, from milk to coffee to beer
