How to Safely Make Fish a Part of Your Diet

Caution: Consult with your diabetes care team before starting a lower-carbohydrate meal plan. Diabetes medications such as insulin or oral drugs that stimulate insulin production (sulfonylureas or meglitinides) will need adjustment to prevent hypoglycemia (low blood glucose) when carbohydrate intake is decreased. In addition, blood glucose levels need to be checked more often.

How Often Should You Eat Fish?

| Aug 1, 2005

The American Heart Association (AHA) recommends that people consume omega-3 fatty acids, found in the flesh of oily fish, for their heart-protective benefits. However, some types of fish contain high levels of contaminants, including mercury.

For most people, the benefits of eating fish outweigh the risks. A study published in the Journal of the American Medical Association in 2002 found that omega-3s make blood less likely to form clots that cause heart attacks, and they also protect against potentially fatal irregular heartbeats. In addition, omega-3s raise levels of HDL (“good”) cholesterol slightly and can significantly help lower triglycerides, which is good news especially for people with diabetes, who have an increased risk of heart disease. The goals for healthy fasting blood triglyceride levels are less than 150mg/dl.

How Often Should You Eat Fish?

The AHA recommends that most people eat at least two 3-ounce servings of a variety of seafood per week. Although there are vegetarian sources of omega-3 fats found in canola oil, walnuts, ground flax seeds and flax seed oils, only fish contains the preformed essential fats, eicosapentaenoic acid (EPA) and docosahexaenoic (DHA) acid. Fatty fish such as salmon, trout, herring, mackerel, sardines, halibut and tuna have higher levels of EPA and DHA, although the amount varies depending upon the livelihood of the fish.

In September l994, the U.S. Food and Drug Administration (FDA) approved the following claim that appears on the labels of foods containing omega-3 fatty acids:

Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease. One serving of [name of food] provides [x] grams of EPA and DHA omega-3 fatty acids. (See nutrition information for total fat, saturated fat and cholesterol.)

The recommended 6 ounces of fish per week is designed to provide approximately 6,000 mg (6 grams) of EPA with DHA per week (see the chart on page 31).

A Caution for Pregnant and Nursing Women

The Environmental Protection Agency (EPA) and the FDA advise women who might become pregnant, are pregnant or are nursing (as well as young children) to monitor the amount and type of fish they eat to reduce exposure to mercury, a toxic contaminant which can accumulate in the body and cause harm, especially to the developing fetus.

Concentrated amounts of mercury are highest in older, larger, predatory fish. Women and children in the higher-risk group are advised to avoid shark, swordfish, king mackerel and tilefish altogether. They are advised instead to eat a variety of seafood low in mercury such as shrimp, canned light tuna, salmon and pollock and to limit consumption to 12 ounces per week.

Albacore white tuna is higher in mercury than canned light tuna and should be limited to no more than 6 ounces per week.

Other people not in the risk category are advised to limit their consumption of shark, swordfish, king mackerel and tilefish to 6 to 7 ounces per week. Eating a variety of other fish is recommended to reduce the potentially negative effects of mercury and environmental pollutants such as polychlorinated biphenyls (PCBs). Whenever possible, select wild or line-caught fish rather than farm-raised, because farmed fish may have higher levels of contaminants. In addition to receiving feed that may contain toxins, farm-raised fish also contain added colorings, antibiotics and other medicines to protect them against disease spread in the crowded farm environment. There is also concern that the feed given to farmed fish to “fatten them up” might produce fish with more harmful fats that are not heart-healthy.

What If You Don’t Like Fish?
Supplementing With Omega-3s

If you don’t like fish or don’t eat it for other reasons, vegetarian sources of omega-3s (walnuts, canola oil, ground flax seeds and flax oil) are better than nothing, but you might also consider taking a fish oil supplement. The U.S. government does not have a general recommendation for Americans, but a few major health organizations suggest an amount anywhere from ½ to 1 gram (500 mg to 1,000 mg) of combined EPA/DHA per day, or 3.5 to 7 grams per week. Good news: Fish oil supplements have lower levels of mercury than the fish itself, according to recent tests.

The American Heart Association does advise that patients with documented cardiovascular disease consume 1 gram of EPA+DHA daily from fish and supplements, when necessary. People with elevated triglycerides are advised to consume 2 to 4 grams of EPA+DHA per day, taken in supplement form, under a physician’s supervision.

Purchasing fish oils can be confusing since each capsule usually contains 1 gram (1,000 mg) of total fish oil, but the amounts of DHA and EPA vary. Many brands provide only 180 mg of EPA and 120 mg of DHA per pill. So, it may be necessary to take one to three pills per day to receive a therapeutic dose. To minimize possible indigestion or gastric upset from fish oil supplements, take them with a meal.

Another source of the omega-3 fat DHA are eggs from chickens that are fed their natural diet (leafy greens, insects, worms) and special eggs from chickens fed a fortified diet that contains flax seeds, fish oil or algae. They vary in the amount of omega-3 fats, which is usually printed on the label.

DHA supplements produced from a special algae are also available in pill form. Cod liver oil is usually not recommended since it may contain excessive amounts of the fat-soluble vitamins A and D, which can be toxic. One concern regarding taking large amounts of fish oil is its ability to thin the blood, which may be an issue for people with bleeding disorders, people taking prescription blood thinners such as Coumadin (warfarin) and those expecting to undergo surgery. Consult with your diabetes care team and physician about supplementing with omega-3s.

Note: 1,000 mg = 1 gram; 500 mg = 0.5 grams

Caution: Fish oil supplements can trigger potentially deadly heart rhythms in people with a history of abnormal heart rhythms according to a multi-center randomized study reported in the June 15 Journal of the American Medical Association. The 200 study participants all had a history of serious abnormal heart rhythms and had implanted defibrillators that shock a heart back into normal rhythm. During the study 65 percent of the participants who took fish oil supplements developed rhythm disturbances over a six month period, compared with 35 percent in the placebo group. Researchers were not able to explain this unexpected finding.

Average amounts
EPA + DHA in 3-ounce serving (grams)
0.5 grams = 500 mg
1.0 grams = 1000 mg
Amount required to provide 1 gram of EPA+DHA per day
Salmon 0.7 to 1.8 grams 2 to 4.5 ounces
Herring 1.7 grams 1.5 to 2.5 ounces
Trout 0.8 to 1.0 gram 3 to 3.5 ounces
Sardines 1.0 to 1.7 grams 2 to 3 ounces
Halibut 0.4 to 1.0 gram 3 to 7 ounces
Catfish 0.2 gram 15 to 20 ounces
Shrimp, crab, lobster 0.2 to 0.4 gram 7 to 12 ounces
Source: Circulation, 2002;106:2747

For More Information

The EPA has a Web site with links to state, territory and tribal fish advisory programs. Go to and click on your state. You will be redirected to a site with local information. For more information on fish and your health, type “fish” into the search box on these Web sites:

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