whereas the average consumption was between 45 mg and 115 mg per day of the women in the study, similar to a Canadian study. Brain and visual functions A major structural component of the mammalian central nervous system, DHA is the most abundant omega−3 fatty acid in the brain and retina. Brain and retinal function rely on dietary intake of DHA to support a broad range of cell membrane and cell signaling properties, particularly in grey matter and retinal photoreceptor cell outer segments, which are rich in membranes. A systematic review found that DHA had no significant benefits in improving visual field in individuals with retinitis pigmentosa. Nutrition Ordinary types of cooked salmon contain 500–1500 mg DHA and 300–1000 mg EPA per 100 grams. Additional rich seafood sources of DHA include caviar (3400 mg per 100 grams), anchovies (1292 mg per 100 grams), mackerel (1195 mg per 100 grams), and cooked herring (1105 mg per 100 grams). Brains from mammals are also a good direct source. Beef brain, for example, contains approximately 855 mg of DHA per 100 grams in a serving. Discovery of algae-based DHA In the early 1980s, NASA sponsored scientific research on a plant-based food source that could generate oxygen and nutrition on long-duration space flights. Certain species of marine algae produced rich nutrients, leading to the development of an algae-based, vegetable-like oil that contains two polyunsaturated fatty acids, DHA and arachidonic acid. Use as a food additive DHA is widely used as a food supplement. It was first used primarily in infant formulas. In 2019, the US Food and Drug Administration published qualified health claims for DHA. Some manufactured DHA is a vegetarian product extracted from algae, and it competes on the market with fish oil that contains DHA and other omega-3s such as EPA. Both fish oil and DHA are odorless and tasteless after processing as a food additive. Studies of vegetarians and vegans Vegetarian diets typically contain limited amounts of DHA, and vegan diets typically contain no DHA. In preliminary research, algae-based supplements increased DHA levels. While there is little evidence of adverse health or cognitive effects due to DHA deficiency in adult vegetarians or vegans, breast milk levels remain a concern for supplying adequate DHA to the developing fetus. DHA and EPA in fish oils Fish oil is widely sold in capsules containing a mixture of omega-3 fatty acids, including EPA and DHA.