Last week, I shared the depressing news that omega-3 fatty acids from fish and/or fish oil may not have any positive effects in some diseases, such as heart disease, cancer and multiple sclerosis — a surprise to the medical community. However, omega-3s from these sources may be beneficial in other diseases and disorders, including age-related macular degeneration, dry eye, Alzheimer’s, rheumatoid arthritis, diabetes, anxiety and, ironically, depression. So don’t avoid fish or fish oil yet. Talk to your doctor first. Let’s review some of the studies.
In the Women’s Health Study, there was a significant reduction in risk of developing AMD for those women who ate fish on a regular basis (Arch Ophthalmol. 2011;129(7):921-929). AMD is the leading cause of central vision loss or blindness in patients over 55. The great news is that you don’t have to eat a substantial amount of fish — just one serving per week results in a 42 percent reduction in risk. The fish that had most impact included salmon, mackerel, tuna, bluefish, swordfish and sardines.
I would recommend sardines and salmon, which are lower in mercury than the others and higher in omega-3s. In those who were taking fish oil supplements containing docosahexaenoic acid and eicosapentaenoic acid there were significant, though slightly less robust, reductions in the risk of AMD, 38 percent and 34 percent respectively.
This was a large observational study with 39,000 participants and a mean 10 year follow-up duration. The researchers believe that the mechanism of action may have to do with an anti-inflammatory process, since AMD has underlying inflammation.
AREDS 2 is an ongoing five-year randomized controlled trial, the gold standard of studies, that includes fish oil (clinicaltrials.gov). It will be interesting to see if it reinforces these results.
Alzheimer’s disease is neurodegenerative disease. There are no medications yet to reverse or slow its progression, only to treat its symptoms. Thus, it is crucial to find lifestyle modifications that may prevent and treat its effects. In a recent study, consumption of omega-3s from fish showed a significant reduction in beta-amyloid protein, a nonspecific marker of Alzheimer’s disease, as measured in the blood (Neurology online May 2).
In another study, consumption of fish at least one time a week showed preservation of brain volume, tested using MRI scans, in the hippocampus and frontal lobe. These areas are responsible for memory and cognitive function.
Both studies are encouraging for Alzheimer’s disease prevention (RSNA Abstract SST11-04). In yet another study, fish oil seemed to reduce the progression of cognitive impairment in patients with very mild Alzheimer’s disease (Arch Neurol. 2006;63:1402-1408).
In the May 24 article, I wrote about a meta-analysis that showed reduction in joint pain and morning stiffness in those who consumed fish oil (Pain. 2007 May;129(1-2):210-23).
These are two of the most common complaints of patients with rheumatoid arthritis.
Omega-3 fatty acids seem to play a role in prevention of type 2 diabetes. In the Cardiovascular Disease Study, there was a 36 percent reduction in the risk of developing diabetes for those who consumed the most omega-3s (Am J Clin Nutr. 2011;94(2):527-33).
The study was unique in that it tested the levels of DHA and EPA in the blood, a quantitative approach, and determined that participants with the highest levels of these omega-3s were least likely to develop the disease.
This was an observational study with 3,000 participants over a 10-year period. These are encouraging results and may indicate another way to reduce diabetes risk.
Dry eye syndrome
The prevalence of dry eye syndrome increases with age and is a common problem, with a higher prevalence among women (Am J Ophthalmol. 2003;136(2):318-26). In the Women’s Health Study, omega-3 fatty acids reduced the risk of dry eye by 17 percent (Am J Clin Nutr. 2005; 82(4):887-93). The omega-3s may work by blocking pro-inflammatory factors in the eye. The best results were found with tuna: one serving per week reduced risk by 19 percent, while two servings reduced risk by a whopping 68 percent. Interestingly, a high omega-6 (pro-inflammatory) to omega-3 ratio increased the risk of dry eye 2.5 times. The typical American diet is low in omega-3s but very high in omega-6s. Included in this latter category are processed foods; meats — especially red meat; dairy such as cheese, whole milk and butter; and certain processed oils. These are foods that are high in fat, but not good fats.
Omega-3s play a potentially significant role in many diseases, but not in all. There is greater upside for omega-3 fatty acids than downside, except as it relates to prostate cancer risk. However, just as with other substances, it may be better to obtain omega-3s from fish than to rely on fish oil. One thing is sure: We get too many omega-6s and not enough omega-3s in our diet and thus may have a higher propensity toward inflammation, which promotes chronic diseases.
Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, go to the website www.medicalcompassmd.com and/or consult your personal physician.