The stink about fish oil, and why it matters to your family
Posted August 28
A wild-caught, fatty fish is one of the most healthy things people can eat, nutritionists say. The evidence on the briny wonders of fish-oil supplements, however, seems to come and go with the tide.
For every study touting fish oil as a remedy for anxiety, arthritis or heart health, another shows no benefit — and occasionally, even harm — from supplementing one's diet with oil pressed out of anchovies and sardines. (Sorry, but no, manufacturers aren't filling capsules with oil from free-range Alaskan sockeye.)
Within the past two months, one study has shown fish oil can help heart-attack patients recover. Another warns that poor-quality oil kills baby rats and that pregnant women should shun it. Despite a growing stack of contradictory laboratory results, 1 in 10 American families buys fish-oil supplements. They're the third most popular supplement, after vitamins and minerals.
Nutritionists, however, caution consumers to closely examine what they're buying because the benefits — if any — are closely linked to the quality of the product.
Marion Nestle, a professor at New York University and author of several books on food and nutrition, isn't a fan.
"The secret of healthful diets is to eat a wide variety of relatively unprocessed foods in amounts that keep calories in balance, and to save junk foods for special occasions. Fish — but not fish sticks — fall into the 'relatively unprocessed' category and are fine to eat if you like them," she said. "Fish oil is another matter. The studies say that eating fish is associated with good health, but the benefits do not show up with fish oil supplements."
But Shawn Talbott, a nutritionist who holds a doctorate in nutritional biochemistry from Rutgers University, says fish oil is one of a few things he routinely recommends.
“Most people can probably benefit from it," he said. "In general, it’s good for the heart. In general, it’s good for the brain."
On its website, The Mayo Clinic lists 55 conditions for which people have used fish-oil supplements. They include cancer, bipolar disorder, aggression, migraines, liver disease and psoriasis — as well as improving athletic performance.
The alphas of omega-3s
While fish oil may seem like a newcomer to the supplement shelf, it’s been used for medicinal purposes for thousands of years. Hippocrates and Pliny mention it as a treatment, although their dolphin liver oil and whale blubber wouldn't pass public muster today. Cod liver oil has been a popular folk remedy for centuries, both taken internally and applied to the skin.
The fish oil in your cabinet today, however, is not your grandmother’s cod liver oil.
It’s pressed from the flesh, not just the liver, of oily fish and contains more of the omega-3 fatty acids people need for optimal function of the brain and cardiovascular system. The omega-3s found in fish are colloquially known as eicosapentaenoic acid and docosahexaenoic acid.
While people get omega-3s when they eat lamb, beef, eggs and poultry, the highest concentrations are in cold-water fish, like salmon, mackerel and herring.
Fewer than 20 percent of people eat as much seafood as the government’s dietary guidelines recommend (8 ounces a week, averaging out to 250 milligrams of DHA and EPA each day). And people with certain conditions, high cholesterol chief among them, need higher amounts than the American Heart Association’s recommendation of 1 gram per day.
Dr. James Fang, chief of cardiovascular medicine at the University of Utah School of Medicine, tends to be skeptical of vitamins and supplements. He notes that scant Food and Drug Administration oversight over the industry means you can’t be sure if an over-the-counter capsule contains fish oil or Crisco.
The FDA worries about that, too, and recently announced that it's strengthening its guidelines regarding new ingredients added to the more than 55,000 dietary supplements sold in the U.S. Another 5,500 come on the market every year.
Regarding fish oil, however, both the FDA and Fang are more accommodating.
“There is a significant amount of scientific literature supporting evidence for fish oil. It helps with inflammation, with cholesterol, with the membranes of heart cells. It also can help with dangerous heart rhythms,” Fang said.
He recommends prescription-grade fish oil for his patients struggling to lower their triglycerides, the fat in our blood that can lead to heart disease when levels are too high because of overeating, drinking too much alcohol, or diabetes and other conditions.
In the latest study, published Aug. 2 in the journal Circulation, Boston researchers found that patients who took large doses of fish oil (4 grams daily, for six months) after a heart attack had less inflammation and reduced scarring than those given a placebo.
Fang is a friend of the study's senior author, Dr. Raymond Y. Kwong, director of Cardiac Magnetic Resonance Imaging at Brigham and Women’s Hospital in Boston. He agreed that the research seems to suggest supplementation is safe and effective in large doses for people who have had heart attacks.
But he noted that the study involved just 360 people, and while it showed improvement in the structure of the heart, the benefits have not been shown to extend to what people care most about: feeling better and living longer.
This is a problem with fish oil and many other supplements. Unless you're being examined and analyzed as part of a well-financed study, there's usually no way to know if it's really improving your health. It's a matter of faith, "nutrition insurance," as Talbott said.
On the other hand, supplements can cause visible and unwanted side effect, and those of fish oil are infamous: diarrhea, gas, nausea and bad breath, among them. Some people say putting fish oil in the freezer eliminates gastrointestinal issues, but Talbott says that's urban legend.
“There are a couple of ways to get around it. If you take it with a meal, that will lessen the tendency to burp up a fish taste. Or take it at night before you go to bed; that’s what I do,” he said.
Quality is key
Talbott said the quality of the oil makes a difference: the better quality, the fewer side effects. The quality also plays a role in its safety.
In a study published July 6 in the American Journal of Physiology, New Zealand researchers said 3 in 10 baby rats whose mothers consumed oxidized fish during pregnancy died after birth. There was no effect on the pups born to mothers who had been given a placebo or fresh fish oil.
Because of ethical constraints, no similar test would be performed on pregnant women, but the findings were troubling enough that the researchers concluded pregnant women shouldn't take fish-oil supplements until more research is done.
"Of course there are contradictory studies. The studies focus on single nutrients, ingredients, or foods when almost everyone eats diets that contain many different foods and vary enormously from day-to-day. Fish contains many useful nutrients but all of them can also be obtained from other foods," said Nestle.
Fang, meanwhile, notes many of the studies on fish-oil supplementation are observational versus randomized trials.
Whether fish oil will help an individual or not depends largely on the condition that is being treated and the dose and quality of the supplement. Like all oils, fish oil deteriorates when exposed to air and light, and it turns rancid with age.
That's why people shouldn't buy the biggest, cheapest bottle of fish oil they can find, Talbott said. A mid-priced variety can be fine, but consumers should check labels to get the highest volume of DHA and EPA per serving they can find. Store it somewhere cool, and away from light.
Fang also suggests checking with a pharmacist about how fish oil reacts with other medication or supplements. Fish oil thins the blood, which can be a problem for people who take prescription blood thinners. (An online interaction checker can help, too. One at Medscape, for example, notes that a combination of fish oil and aspirin increases the risk of bleeding.)
Or, you can forget about the side effects, reactions and the potential for fish breath, and do as Fang does: Just eat more fish.
"I think we'd all prefer to eat it than take pills," he said.