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The eyes' ability to adjust to changes in illumination, referred to as light and dark adaptation, varies between individuals. Dark adaptation, in particular, is critical to survival in low light and is responsible for what is commonly referred to as “night vision.” A recent study indicates that supplementation with omega-3 fatty acid-rich fish oil may improve night vision in humans.
Omega-3 fatty acids are polyunsaturated fats that are essential for human health. They include alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is found mainly in plant oils such as flaxseed, soybean, and canola oils. DHA and EPA are found in fish and other seafood. The human body can convert some ALA into EPA and then to DHA, but the process is very inefficient. Omega-3 fatty acids accumulate in the human retina and play instrumental roles in vision.
The study involved 20 adults who took four omega-3 fatty acid-rich fish oil supplements three times daily, providing approximately 3 grams of EPA and 1 gram of DHA, for four weeks. Six weeks after the last supplementation, the participants' blood concentrations of omega-3 fatty acids were measured and their ability to adjust to low light was assessed.
Participants who took EPA/DHA-rich fish oil supplements for four weeks demonstrated a 25 percent improvement in their ability to identify numbers in low light, compared to those who took a placebo. These changes in visual acuity were attributed to increased levels of omega-3 fatty acids in the participants' blood.