Novel study linked omega-3 DHA in fish oil to enhanced adaptation to low-light conditions 01/02/2020
The omega-3 fatty acid known as DHA is a critical component of our eyes, enabling our ability to see.
Like EPA, its companion omega-3 in seafood, we need DHA for basic body functions — but only DHA is essential to vision.
Before we get to the findings of a new British clinical trial, let's recall why omega-3 DHA is so important to eye health and visual acuity.
Why is omega-3 DHA so vital to vision?
Omega-3 DHA is a key structural, functional, and protective component of the eye’s retina — the layer of tissue that converts light into signals sent to the brain.
The retina uses specialized cells called rods and cones to process light — and both types of “photoreceptor” cell abound in and depend upon omega-3 DHA. This fact likely explains the findings summarized in Omega-3s Linked to Eye Health … Again and related articles in the Omega-3s & Eye Health section of our news archive.
A bodily shortage of DHA leads to a lack of retinal DHA, which in turn reduces visual acuity — and can raise the risk for age-related macular degeneration (AMD) with potentially crippling effects on vision.
(Unfortunately, the average American's diet lacks omega-3s as well as the eye-protecting antioxidants lutein and zeaxanthin. See “American diet can cause DHA deficiency”, below and Even America's Shore-Dwellers Lack Omega-3s.)
Omega-3 DHA directly protects the retina's pigment cells from damage by oxidizing free radicals, and retinal cells also use DHA to make a guardian compound called neuroprotectin D1 that further protects retinal pigment cells. And research in rodents suggests that DHA exerts the additional protective effects described in New Eye Benefit Seen in Omega-3s.
Together with DHA’s critical structural and functional roles, its protection of retinal cells probably helps explain why people who eat fish frequently or who have higher blood levels of DHA have significantly lower rates of AMD (Chong EW et al. 2008; Merle BM et al. 2014; Souied EH et al. 2015; Wu J et al. 2017).
Let’s look at some new — apparently unprecedented — clinical evidence suggesting that omega-3 fish oil can enhance night vision to a very substantial extent.
Omega-3 DHA boosted night vision in British clinical
Scientists from Britain’s Loughborough University set out to test whether a standard omega-3 fish oil providing DHA (and EPA) could improve people's ability to respond to dimming light — also known as “dark adaptation capacity”.
The British team recruited 19 volunteers and asked them to identify a series of numbers of ever-decreasing brightness, displayed on a handheld device (McMurchie B et al. 2019).
The volunteers then took four omega-3 fish oil capsules — each providing 260mg DHA and 780mg EPA, for a total of 1,040mg of DHA daily — every day for four weeks.
After taking the fish oil for one month, they visited the labs again to repeat the same test of their eyes’ dark-adaptation abilities — with encouraging results.
On average, after taking fish oil daily for four weeks, the volunteers could identify images that were 25% fainter than the faintest images they could identify before the month of daily fish oil.
Confirming that the omega-3 fish oil produced the visual benefit, the volunteers’ night-vision capacities returned to their original levels about six weeks after they stop taking supplemental fish oil.
And, proving that omega-3 DHA was responsible for this benefit of the fish oil, the scientists found that rising and falling DHA blood levels closely corresponded to gains and declines in the volunteers' night-vision capacities.
The study’s lead co-author, Dr. Paul Kelly, noted the novelty of that finding: “This is the first time dark-adaptation has been linked to fish oil’s [omega-3 DHA] fatty acids via direct measurement of amounts making it into the blood.”
(It's likely that — if taken for the longer time required to reach similarly high blood levels — a daily dose of DHA lower than the one used in this trial would yield similar visual benefits.)
Dr. Kelly underscored the importance of their findings and called for bigger, placebo -controlled trials to confirm them: “The 25% figure is a significant improvement in someone’s capabilities, especially given that it comes via a simple supplement regimen. Ideally, the next phase of this work would be to extend the range of individuals tested this way — alongside placebos — in order to give a bigger data set to analyze.”
And he noted the practical implications of their research: “You could imagine this finding benefitting anyone who requires their night vision to be as good as possible — for example, police, people in the military, and forensic scientists looking for fluorescent evidence in the dark.”
American diet can cause DHA deficiency
The body can make very small but potentially adequate amounts of DHA from the only omega-3 fat found in plant foods, called ALA. Flaxseed, flaxseed oil, and canola oil are the only common foods high in omega-3 ALA; smaller amounts occur in hemp seeds, chia seeds, avocados, walnuts, DHA-fortified eggs, and leafy, dark green vegetables.
However, the body must first convert dietary ALA into very small amounts of EPA and then convert some of that EPA into even smaller amounts of DHA.
But the average American gets too few omega-3s of any kind, while the body’s limited ability to make DHA from the omega-3 ALA in certain plant foods and oils gets constricted by high intakes of competing omega-6 fats from vegetable oils. And because it’s laden with omega-6-laden vegetable oils, the average American's diet delivers an extreme, historically unprecedented excess of omega-6s.
Fortunately, we can avoid that omega-3-conversion bottleneck by taking two steps: 1) avoid oils high in omega-6 fats and foods made with them and 2) eat plenty of of wild fish — especially fatty species like salmon, sardines, and albacore tuna (whether fresh/frozen or canned) — and/or take omega-3 fish oil.
Note: Due to the grains, plant oils, and seeds in its cheap, man-made diet, farmed salmon is typically high in omega-6 fats, making it an inferior, less healthful source of omega-3s versus wild salmon. Compared with farmed salmon, farmed tilapia and catfish are even higher in omega-6s and much lower in omega-3s. For more on this topic, see Farmed Fish Possess Unhealthful Fat Profiles and Farmed Salmon's Diet Yields Unhealthful Cardiovascular Effects.
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