Omega-3 FA most likely reduce serum triglyceride levels by modulating very-low-density lipoprotein (VLDL) and chylomicron metabolism. There is a consistent finding in the literature that the end effect of fish oil is decreased hepatic secretion of VLDL17—the major endogenous source of triglycerides. This effect occurs most likely through multiple mechanisms, including: (1) decreased synthesis of triglycerides because these omega-3 FA may not be the preferred substrates of the enzyme diacylglycerol O-acyltransferase,18 or they may interact with nuclear transcription factors that control lipogenesis19; cellular metabolism consequently shifts toward a decrease in triglyceride synthesis and an increase in FA oxidation; and (2) the promotion of apolipoprotein B degradation in the liver through the stimulation of an autophagic process.20 This means that fewer VLDL particles can be assembled and secreted. Fish oil may also accelerate VLDL and chylomicron clearance21 by inducing lipoprotein lipase activity.22
The Japanese notably have the lowest levels of coronary heart disease mortality and atherosclerosis among developed nations — a phenomena that has been largely subscribed to diet. However, even within Japan, a 10-year study of over 41,000 people found that higher intakes of omega-3s were associated with lower risks of nonfatal coronary events (8). A more recent study also found that Japanese with higher omega-3 index levels (10%) had a lower risk of fatal coronary heart disease than those with a lower omega-3 index levels (8%) (9). The study begs the question of whether maybe even the Japanese have room to improve their omega-3 intake and whether 8% should be considered the lower limit of a desirable range.
I now suspect that those thousands of gel-covered capsules I’ve swallowed over the years may have done little more than enrich the pockets of supplement producers and sellers. A number of extensive analyses have been conducted, some supporting and others refuting the value of fish oils to the cardiovascular system, along with studies of other purported health benefits that also have had mixed results.
The three types of omega-3s are APA, EPA and DHA. The first is a medium-chain fatty acid and must be converted into EPA before being synthesized by the body, and only about 1 percent of the APA consumed is able to be converted. EPA and DHA are already in a form ready to be synthesized (and are the subject of most scientific research regarding omega-3s).
Omega-3 fatty acids are frequently in the news regarding their health benefits (or doubts in some cases). Two types of omega-3s in particular - eicosapentaenoic acid (EPA) and docohexaenoic acid (DHA) – are known to be essential fatty acids. “Essential” refers to the fact that our cells need these fatty acids in order to function normally. But the body cannot make them from other fats, which means it’s “essential” we supply them in our diet or through supplementation.
"All these diseases have a common genesis in inflammation," says Joseph C. Maroon, MD, professor and vice chairman of the department of neurological surgery at the University of Pittsburgh School of Medicine. Co-author of Fish Oil: The Natural Anti-Inflammatory, Maroon says that in large enough amountsomega-3's reduce the inflammatory process that leads to many chronic conditions.
Other suspected health benefits of omega-3s and fish are less well established and need further study. They include suggestions of a reduced risk of breast cancer, colorectal cancer and possibly advanced prostate cancer, all related to eating fish rather than taking supplements. Some observational studies have associated omega-3s to a lower risk of cognitive decline, Alzheimer’s disease and dementia, as well as age-related macular degeneration.
Finally, in order for AA to be converted into inflammatory products it must be released from phospholipids (part of the cell membrane) using the enzyme phospholipase A2 and then converted by the enzyme cyclooxygenase. EPA utilises both of these enzymes, so if EPA levels are increased in the diet, it attracts enzyme away from AA to EPA – again giving rise to anti-inflammatory products instead of inflammatory ones.
It’s no surprise that fish — particularly cold-water fatty fish like salmon, mackerel, and anchovies — are rich in omega-3s. It’s called fish oil for a reason, right? Mackerel, for instance, may have more than 3300 mg of omega-3 per serving — that’s more than 6 times the recommended per day dose for healthy adults. Not a huge fish connoisseur? Try some of the quick, simple recipes in Cooking with Fish Like a Pro, an accessible collection of fish recipes to suit every palate.
Fish oil contains two very important omega-3 PUFAs. I’m talking about docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). DHA and EPA are sometimes called the marine omega-3s because they mainly come from fish. Some of the best fish to eat to obtain fish oil from in your diet include wild-caught salmon, herring, white fish, sardines and anchovies.
Pro Omega 3 Intensive Formula is a more convenient source of EPA and DHA than regular marine fish oils for those who would like to supplement their diets with higher amounts of these important omega 3 fatty acids. Our formula contains concentrated marine fish oil, providing enriched levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Plus, it’s lower in saturated fatty acids than regular marine fish oil. For those who don’t eat fish or want to add more omega to their diet, Omega 3 supplements are a convenient way of incorporating these important nutrients into your everyday life. This fish oil supplement is strictly screened for the absence of any toxic metals and chemicals, and is completely free of cholesterol. The oil is carefully processed and handled to avoid oxidation.†
There’s more good news when it comes to fish oil and eye health, and it’s just not just for diabetic this time. Fish oil has been shown to reverse age-related eye disorders. In March 2014, French researchers evaluated 290 patients with age-related macular degeneration (AMD), and they discovered that dietary oil fish and seafood intake were significantly lower in AMD patients. Due to the high EPA and DHA levels in fish oil, it was concluded that this kind of nutritional intervention could especially benefit those at high risk for neovascular age-related macular degeneration. (24)
In the United States, the Institute of Medicine publishes a system of Dietary Reference Intakes, which includes Recommended Dietary Allowances (RDAs) for individual nutrients, and Acceptable Macronutrient Distribution Ranges (AMDRs) for certain groups of nutrients, such as fats. When there is insufficient evidence to determine an RDA, the institute may publish an Adequate Intake (AI) instead, which has a similar meaning, but is less certain. The AI for α-linolenic acid is 1.6 grams/day for men and 1.1 grams/day for women, while the AMDR is 0.6% to 1.2% of total energy. Because the physiological potency of EPA and DHA is much greater than that of ALA, it is not possible to estimate one AMDR for all omega−3 fatty acids. Approximately 10 percent of the AMDR can be consumed as EPA and/or DHA. The Institute of Medicine has not established a RDA or AI for EPA, DHA or the combination, so there is no Daily Value (DVs are derived from RDAs), no labeling of foods or supplements as providing a DV percentage of these fatty acids per serving, and no labeling a food or supplement as an excellent source, or "High in..." As for safety, there was insufficient evidence as of 2005 to set an upper tolerable limit for omega−3 fatty acids, although the FDA has advised that adults can safely consume up to a total of 3 grams per day of combined DHA and EPA, with no more than 2 g from dietary supplements.
About the only exception are wild-caught Alaskan salmon and very small fish like sardines. The highest concentrations of mercury are found in large carnivorous fish like tuna, sea bass, and marlin. You may need to be especially cautious of canned tuna as well, as independent testing by the Mercury Policy Project found that the average mercury concentration in canned tuna is far over the "safe limits" of the Environmental Protection Agency (EPA).
Interestingly, the results are also consistent with our recent findings that somatic anxiety is associated with omega-3 PUFA deficits and the genetic risks of PUFA metabolic enzyme cytosolic phospholipase A2 in major depressive disorder62,63 and interferon α–induced neuropsychiatric syndrome.63,64 Brain membranes contain a high proportion of omega-3 PUFAs and their derivatives and most animal and human studies suggest that a lack of omega-3 PUFAs in the brain might induce various behavioral and neuropsychiatric disorders,16,65-70 including anxiety-related behaviors.12,18,19,32,49,71 Emerging evidence suggests that omega-3 PUFAs interfere with and possibly control several neurobiological processes, such as neurotransmitter systems, neuroplasticity, and inflammation,12,72 which is postulated to be the mechanism underlying anxiety and depression.
Of great clinical importance, EPA and DHA supplementation during pregnancy has been associated with longer gestation and increased concentrations of EPA and DHA in fetal tissues (21). In 2005, preterm births accounted for 12.7% of all births in the United States, increasing the likelihood of health complications (22). Carrying a baby to term is very important because prematurity is the cause of various infant diseases and can lead to death; preterm delivery is an underlying factor for 85% of the deaths of normally formed infants (23). One mechanism by which EPA and DHA may decrease the incidence of preterm birth is by decreasing prostaglandin E2 and prostaglandin F2α production, therefore reducing inflammation within the uterus, which could be associated with preterm labor (21, 24). Several studies investigated EPA and DHA intake during pregnancy and its correlation with longer gestation. Conclusions were that EPA+DHA supplementation during pregnancy delayed the onset of delivery to term or closer to term; however, supplementation did not delay delivery to the point of being post-term (20, 23, 25). This supports the evidence that EPA+DHA ingestion leads to optimal pregnancy length. EPA+DHA supplementation reduced the HR of preterm delivery by 44% (95% CI: 14–64%) in those who consumed relatively low amounts of fish and 39% (95% CI: 16–56%) in those who consumed medium amounts of fish; however, a level of statistical significance was not met (P = 0.10) (23). The Judge et al. (20) study found that women who had DHA supplementation from gestation week 24 until full-term delivery carried their infants significantly (P = 0.019) longer than did the women in the placebo group. One study found that DHA supplementation after gestation week 21 led to fewer preterm births (<34 wk of gestation) in the DHA group compared with the control group (1.09% vs. 2.25%; adjusted RR, 0.49; 95% CI: 0.25–0.94; P = 0.03). Also, mean birth weight was 68 g heavier (95% CI: 23–114 g; P = 0.003) and fewer infants were of low birth weight in the DHA group compared with the control group (3.41% vs. 5.27%; adjusted RR, 0.65; 95% CI: 0.44–0.96; P = 0.03) (25).
Ramakrishnan, U., Stein, A. D., Parra-Cabrera, S., Wang, M., Imhoff-Kunsch, B., Juarez-Marquez, S., Rivera, J., and Martorell, R. Effects of docosahexaenoic acid supplementation during pregnancy on gestational age and size at birth: randomized, double-blind, placebo-controlled trial in Mexico. Food Nutr Bull 2010;31(2 Suppl):S108-S116. View abstract.
Fish oil is very beneficial for pregnant women because the DHA present in it helps in the development of the eyes and brain of the baby. It also helps to avoid premature births, low birth weight, and miscarriages. Research conducted in Denmark, which involved 8,729 pregnant women, concluded that a diet with low amounts of fish resulted in a higher risk of premature or preterm babies.
Corresponding Author: Yutaka J. Matsuoka, MD, PhD, Division of Health Care Research, Center for Public Health Sciences, National Cancer Center Japan, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan (firstname.lastname@example.org); Kuan-Pin Su, MD, PhD, China Medical University Hospital, No. 2, Yude Road, North District, Taichung City, Taiwan 404 (email@example.com).
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What are the benefits of cod liver oil? This article provides detailed information on the health benefits associated with cod liver oil, and its potential therapeutic properties. This article looks at some of the claims that cod liver oil might improve cardiovascular health, ease joint stiffness caused by arthritis, and repair wounds. Read on to learn more. Read now
Meta‐analysis and sensitivity analyses suggested little or no effect of increasing LCn3 on all‐cause mortality (RR 0.98, 95% CI 0.90 to 1.03, 92,653 participants; 8189 deaths in 39 trials, high‐quality evidence), cardiovascular mortality (RR 0.95, 95% CI 0.87 to 1.03, 67,772 participants; 4544 CVD deaths in 25 RCTs), cardiovascular events (RR 0.99, 95% CI 0.94 to 1.04, 90,378 participants; 14,737 people experienced events in 38 trials, high‐quality evidence), coronary heart disease (CHD) mortality (RR 0.93, 95% CI 0.79 to 1.09, 73,491 participants; 1596 CHD deaths in 21 RCTs), stroke (RR 1.06, 95% CI 0.96 to 1.16, 89,358 participants; 1822 strokes in 28 trials) or arrhythmia (RR 0.97, 95% CI 0.90 to 1.05, 53,796 participants; 3788 people experienced arrhythmia in 28 RCTs). There was a suggestion that LCn3 reduced CHD events (RR 0.93, 95% CI 0.88 to 0.97, 84,301 participants; 5469 people experienced CHD events in 28 RCTs); however, this was not maintained in sensitivity analyses – LCn3 probably makes little or no difference to CHD event risk. All evidence was of moderate GRADE quality, except as noted.
Increased consumption of omega 3 fats is widely promoted globally because of a common belief that that it will protect against heart disease. There is more than one possible mechanism for how they might help prevent heart disease, including reducing blood pressure or reducing cholesterol. Omega 3 fats are readily available as over-the-counter supplements and they are widely bought and used.
Several large studies have linked higher blood levels of long-chain omega-3s with higher risks of prostate cancer. However, other research has shown that men who frequently eat seafood have lower prostate cancer death rates and that dietary intakes of long-chain omega-3s aren’t associated with prostate cancer risk. The reason for these apparently conflicting findings is unclear.
In addition to depression, chronic stress leads to loss of volume of the hippocampus—and also causes enlargement of the amygdala, the portion of the brain that regulates anxiety and anger.24 When rats were supplemented with omega-3s during exposure to stress, they showed lower corticosterone levels (a marker of stress), and improved learning on a maze—indicating that the omega-3s helped preserve memory and reduce anxiety.24
These low levels are especially bad when compared to the numbers from the Japanese population. In Japan, the average omega-3 index level is more than double that of the average American, with some surveys showing Japanese men consume over 100 g (approximately 3.5 oz) of fish every day. These radically different dietary habits help explain how even those with omega-3 indexes in the lowest 5th percentile of the Japanese population have higher omega-3 index averages than most Americans (8).
An analysis based on data from the Norwegian Women and Cancer Study (NOWAC) with regards to the dangers of persistent organic pollutants (POPs) in cod liver came to the conclusion that "in Norwegian women, fish liver consumption was not associated with an increased cancer risk in breast, uterus, or colon. In contrast, a decreased risk for total cancer was found."
A 2009 metastudy found that patients taking omega-3 supplements with a higher EPA:DHA ratio experienced fewer depressive symptoms. The studies provided evidence that EPA may be more efficacious than DHA in treating depression. However, this metastudy concluded that due to the identified limitations of the included studies, larger, randomized trials are needed to confirm these findings.
A March 2010 lawsuit filed by a California environmental group claimed that eight brands of fish oil supplements contained excessive levels of PCB's, including CVS/pharmacy, Nature Made, Rite Aid, GNC, Solgar, Twinlab, Now Health, Omega Protein and Pharmavite. The majority of these products were either cod liver or shark liver oils. Those participating in the lawsuit claim that because the liver is the major filtering and detoxifying organ, PCB content may be higher in liver-based oils than in fish oil produced from the processing of whole fish.
Thank you for your kind comment. As pointed out above, the main limitation of our meta-analysis is the heterogeneity, which we address several times in our main manuscript. We included studies with several different situations and participants with different underlying diseases, which would also result in wide heterogeneity in our meta-analysis. Based upon our post-hoc analysis, there was some common characteristics among the six trials with nominally significant results, including specific clinical diagnoses (5/6) and, placebo-control (4/6), which had also previously been addressed in our subgroup meta-analysis. Therefore, we suggested future placebo-controlled trials investigating the treatment effect of omega-3 in participants with specific clinical diagnoses should be warranted. In addition, improving underlying specific clinical diagnoses (5/6), good quality (placebo-control (4/6), low drop-out rate (zero in Exp/control groups: 4/6)), and long treatment duration (>= 12 weeks: 4/6) are all good indicators of high quality.
High blood pressure. Fish oil seems to slightly lower blood pressure in people with moderate to very high blood pressure. Some types of fish oil might also reduce blood pressure in people with slightly high blood pressure, but results are inconsistent. Fish oil seems to add to the effects of some, but not all, blood pressure-lowering medications. However, it doesn't seem to reduce blood pressure in people with uncontrolled blood pressure who are already taking blood pressure-lowering medications.