Dr. John Paul SanGiovanni, PhD is chief of the unit on Genetics in Nutritional Neuroscience in the Laboratory of Membrane Biophysics and Biochemistry, National Institute on Alcohol Abuse and Alcoholism, which is a division of the National Institutes of Health. Dr. SanGiovanni, whose research on eye health has been cited more than 12,000 times, spoke with NutraIngredients-USA at the recent GOED Exchange meeting in Seattle.
Critical role in metabolic hot house
Dr. SanGiovanni said both DHA and EPA have critical roles in the retina, which is one of the most metabolically active tissues in the body. It is well known that the macular carotenoids, principally lutein and zeaxanthin, are concentrated in the retina via a dedicated transporter, and are present in the tissue at orders of magnitude greater than in other parts of the body. What is less well-known is that DHA is present in high concentrations, too, where Dr. SanGiovanni said it plays a key role in maintaining healthy cell membranes, where many of the subtle reactions in this highly charged metabolic environment occurs.
“The concentration of DHA in the retina is far higher than in any other tissue. In fact about 60% of the lipids in the retina are DHA,” SanGiovanni said. “It’s very imporant when you talk about cell signaling to have a very fluid membrane, and DHA imparts this characteristic that allows proteins that sit in the membrane to move.”
Strong backing for findings
SanGiovanni said research done as far back as the mid 1990s showed that people with lower risk of AMD had higher levels of DHA in the blood. Subsequent research, looking at intake as opposed to status, showed that people who consume higher amounts of EPA and DHA have about a 30% to 40% lower risk of developing AMD. Dr. SanGiovanni said this finding has been verified at least ten times.
In the case of EPA, San Giovanni said that this essential fatty acid does not have the same structural role in cell membranes as does DHA. But he said that EPA is nonetheless key to the proper functioning of cell signaling, which requires a very rapid response from cell. It is also a precursor to some very important antioxidant molecules, which help to regulate inflammation. The supercharged metabolism of the retina means that a large quantity of oxygen is being turned over every second, which can give rise to excess amounts of reactive oxygen species.