StTUDY after study will say adding fish to your diet is a healthy move.

    Fish oil supplements, though, are a more complicated story.

    Experts advise adults to eat a variety of seafood each and every week. They believe seafood can provide you with healthy amounts of two essential omega-3 fatty acids: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).

    These nutrients play important roles in brain function, normal growth and development, metabolism and curbing inflammation. Our bodies cannot manufacture these fatty acids, so we must consume them.

    Fatty fish, such as salmon, mackerel and sardines, are rich in both DHA and EPA.

    Despite the plentiful options for adding DHA and EPA to our diet, many people prefer to hack the process by taking fish oil supplements, the same way you’d drink vegetable juice instead of eating actual veggies.

    “A lot of people don’t know why they take fish oil,” said R. Preston Mason, a faculty member at Harvard Medical School and president of Elucida Research, a biotechnology research company. “You take fish oil for the omega-3 content. ... People have heard it’s good for you, so they take it. It’s a booming industry.”

    Fish oil is the third most widely used supplement in the United States.

    Though a simple swap appears to make sense to huge numbers of people, the underlying science suggests that fish oil supplements may not do justice to our physical need for omega-3s.

    And, over the years, opinion on its benefits has gone back and forth.

    18th century (and earlier): Fish oil cures what ails you

    Fish oils had been used as a cure for generations in Northern European fishing communities. In particular, citizens of Germany and Britain used cod liver oil to treat rickets, rheumatism, gout and tuberculosis during the 18th century.

    Yet it is widely believed that fishermen of earlier centuries commonly used oils for a range of conditions including wounds, body aches, the common cold and skin diseases. Cod liver oil, as a mass-produced product, dates to the 1700s and 1800s.

    29th century: Fish oil is big business

    Though the Vikings may have begun the disruptive technology of fish oil production, the commercial industry took flight at the beginning of the 19th century in northern Europe and North America. Based mainly on surplus catches of herring, oil production activities found industrial uses in leather tanning, soap production and other non-food products.

    Originally, the residue was used as fertilizer, but since the turn of the 20th century, the oil leftovers have been dried and ground into fish meal for animal feed.

    320th century: Fish oil production becomes more refined

    Some of the older traditions continue unchanged into the 20th century, though the U.N. report notes that a number of options in the fields of energy saving, automation and environmental protection have increased in recent years. Unpalatable species of fish — or so-called industrial fish, including menhaden, sand eel, anchoveta and pout — are reduced into oil by standard methods — essentially, heating, pressing and grinding.

    While Europe may have dominated production in previous centuries, in the latter half of the 20th century, Peru and Chile came to the forefront of the industry, each exporting about 18,000 metric tons of fish oil worldwide. Iceland, Denmark, Norway and the United States also produce fish oil, with all production companies selling mainly to Asia and Europe.

    42010: Fish oil supplements during pregnancy do not prevent postpartum depression

    Fish oil supplements taken during pregnancy have no effect on postpartum depression and do not help babies’ brains develop more quickly, according to a 2010 study published in the Journal of the American Medical Association.

    A team of Australian researchers had expected to find that fish oil had positive effects for the more than 2,000 pregnant women studied. However, the women who took the supplements during their pregnancy were just as likely to experience postpartum depression as those who didn’t and the brains of their babies didn’t appear to grow and develop more quickly than other babies. Yet, the supplements were associated with a reduced risk of preterm birth.

    52011: Fish oil eases ADHD

    symptoms and lessens baby colds

    Fish oil supplements, particularly those with higher doses of EPA, were found to be “modestly effective” in the treatment of attention-deficit/hyperactivity disorder, according to a review published in the Journal of the American Academy of Child & Adolescent Psychiatry.

    After reviewing and analyzing 10 clinical trials involving 699 participants, Yale Child Study Center researchers found “a small but significant effect” demonstrated by omega-3 fatty acid supplementation. Separately, the authors found that supplementation treated symptoms of inattention and hyperactivity. However, they cautioned against using omega-3s in lieu of pharmaceutical treatments.

    Also in 2011, a study published in the journal Pediatrics found that the babies of pregnant women who took fish oil supplements containing DHA had more fortified immune systems.

    62012: Fish oil might help the brain stay young and heal traumatic brain injury

    Accelerated brain aging is more likely to occur in people who eat diets short on omega-3 fatty acids — the kind found in fish oil, according to a study published in the journal Neurology.

    Lead author Dr. Zaldy S. Tan and his colleagues at the University of California, Los Angeles looked at circulating levels of DHA and EPA in the blood of 1,575 people.

    Next, they compared these levels with participants’ MRI brain scans and cognitive test results: problem-solving, multitasking and abstract thinking.

    They discovered that those participants who scored in the bottom 25 percent on various mental tests had lower levels of omega-3 fatty acids in their blood and lower brain volumes — what equates to about two years of brain aging.

    72013: Fish oil supplements linked to increased risk of

    prostate cancer

    Eating a lot of oily fish or taking potent fish oil supplements was associated with a 43 percent increased risk of prostate cancer, according to a Fred HutchinsonCancer Research Center study published online in the Journal of the National Cancer Institute. The researchers also discovered a 71-percent increased risk of aggressive prostate cancer among those consuming fish oil or large amounts of oily fish.

    82015: Fish oil may transform fat cells

    Fish oil may transform fat-storage cells into fat-burning cells, which may reduce weight gain in middle age, according to research conducted in mice and published in Scientific Reports. According to Kyoto University researchers, fish oil not only activates receptors in the digestive tract, it induces storage cells to metabolize fat.

    The scientists fed fatty foods to one group of mice, and a second group ate non-fatty fish oil additive foods. The mice that ate fish oil gained 5 percent to 10 percent less weight and 15 percent to 25 percent less fat than the others.

    92016: Fish oil during pregnancy lowers risk of asthma in children — but are the supplements all they claim to be?

    Women who took fish oil during the last three months of pregnancy lowered the risk of their children developing asthma, according to a Danish study published in the New England Journal of Medicine.

    About 17 percent of children whose moms took fish-oil capsules had asthma by age 3, compared with nearly 24 percent of the children whose mothers were given placebos.

    While this is certainly good news, a very different study of fish oil authored by Harvard’s Mason appeared around the same time.

    “I just wanted to ask the question: What’s actually inside these capsules?” Mason said of his study, which looked at a limited number of popular U.S. fish oil supplements.

    “We were quite surprised to see that in some of these widely used supplements, only a third of the product was the favorable omega-3s, and the balance of them were these other lipids, including saturated fats, which we don’t associate with health benefits.”

    Saturated fats raise our bad cholesterol, or LDL.Mason said he was also surprised to learn the fish oil supplements contain cholesterol.

    “Omega-3s are highly vulnerable to breakdown during manufacturing. They become oxidized or rancid,” Mason said. Along with the challenge of manufacturing these products without damage, most of them come in large shipments sailing the seas.

    “During that process, they are often exposed to elevated temperatures, which will rapidly break them down,” he said, adding that “in the lab, if we expose omega-3s to just normal environmental conditions, within hours, they’re breaking down into these oxidized products.

    “Once they are broken down, certainly they don’t have their favorable benefits that we hope for,” Mason said.

    102017: What’s next for fish oil?

    Looking to the future, Nancy Copperman, a registered dietician and assistant vice president public health and community partnership at Northwell Health, reviewed the latest research. She recommends a simple — if more expensive — option for consumers who want to add fish oil to their diets: “pharmaceutical-grade fish oil supplements that tend to be purer.”

    At the same time, Copperman cautions consumers against believing every health claim, since most only hold true for a narrow group of people researched.

    Since omega-3s are necessary nutrients, Copperman suggests that people stick with eating oily fish rather than taking supplements: When you’re eating more fish, you are most likely eating less beef, including fatty hamburgers.(SD-Agencies)