How eating fish can protect your heart

As someone with a family history of heart problems, I struggle with far-from-perfect cholesterol numbers. I'm ever hopeful for a science breakthrough I can act on. I once ate oats every day for three months in an attempt to nudge my lipid values into healthier ranges; it worked, but alas, not enough. I still enjoy my oat cereal, but I know I need to do more. Lately, I'm eating more fish.

Last October, Harvard scientists analyzed two decades of research and concluded that modest consumption of fish (one to two servings per week), especially salmon, tuna and other types rich in the fatty acids known as omega-3s, reduced risk of heart disease death by 36 percent and overall deaths by 17 percent. The data were so compelling the authors claimed the health benefits of eating seafood outweigh the risks of exposure to environmental contaminants in fish such as methyl mercury or PCBs. (That said, women who are nursing, pregnant or planning to become pregnant and children younger than 12 should avoid fish with higher mercury levels, such as swordfish.)

Ever since my grad-student days I've been intrigued by the story of pioneering epidemiologists who sought to learn why heart disease was practically unheard of in Greenland's Inuit people—despite their diet of high-fat, high-cholesterol whale and seal meat. The scientists discovered that two omega-3 fatty acids predominant in fish—eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA)—were widespread in the Inuit blood and were likely protecting their hearts.

How? When it comes to fats, we are what we eat: our cell membranes reflect the fat content of our diet. When we eat ample omega-3s, our membranes—including those of the heart and blood vessels—are more elastic (that's how fish stay flexible in icy waters). Blood moves through the body more easily, reducing the risk of high blood pressure and blood clots. All this can help prevent hardened arteries and stroke, and lowers risk of an irregular heart rate. Lastly, EPA fights inflammation, a known disease risk factor. Inflammation is the body's normal response to injury, but chronic inflammation seems to play a role in causing hardened arteries and other heart problems.

Plant foods like flaxseed, soybeans, canola and walnuts are good sources of alpha-linolenic acid (ALA), another omega-3 with its own heart benefits. A small amount of ALA is also converted to EPA and DHA in the body, "but at a very slow rate," says William Connor, M.D., a longtime friend of mine and a professor at Oregon Health & Science University who has studied fish and fish oils for more than 30 years. If it's heart-health effects you're after, he emphasizes, "What you want are EPA and DHA, from fish or fish-oil supplements."

But omega-3s are usually lacking in our diets, vastly outnumbered by omega-6 fatty acids common to processed foods made with vegetable oils including safflower and cottonseed. Omega-6s tend to promote inflammation, while omega-3s reduce it. Many experts believe our American diets tilt too much toward omega-6s, and that the best way to restore balance is to boost our intake of omega-3s from any source.

So I'm doing my darnedest to eat more omega-3s. I aim to serve a fatty fish like salmon twice a week, and consider the seafood dishes first in restaurants. I sprinkle walnuts on my salads and make dressings with canola oil.

As ever, moderation is key. Very high intakes of fish-based omega-3s (over 3,000 mg/day) can raise the risk of excessive bleeding or even hemorrhagic stroke. And, like any fat source, omega-3s are still calorie-rich. So focus on substituting (not adding) omega-3s for other fats you eat. After all, the most important thing you can do for your heart is to be at a healthy weight. Without that, keeping your heart healthy is just a fishing expedition.

* Mozaffarian D, Rimm EB; JAMA 2006; 296(15); 1885. **Dietary Reference Intakes, Institute of Medicine.

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What it does:

Scientists have not yet elucidated all of vitamin E's roles, but they hypothesize that it has a role in immune function, DNA repair, the formation of red blood cells and vitamin K absorption.

How much you need:

The RDA in men and women is 23 IU, or 15 milligrams, and because many E-rich foods come from nuts and oils, some low-fat diets may be inadequate in vitamin E.

Food Sources of Vitamin E:

Wheat germ oil. Sunflower seeds, cooked spinach, almonds, safflower oil and hazelnuts.

(2) Zinc

What it does:

Zinc is integral to almost every cell of the human body, from keeping the immune system healthy to regulating testosterone.

How much you need:

The recommended dietary intake for men is 11 mg/day, for women 8 mg/day.

Food Sources of zinc:

Oysters, cooked beef tenderloin, turkey, chickpeas, roast chicken leg, pumpkin seeds, cooked pork tenderloin, plain low-fat yogurt, wheat germ, tofu, dry roasted cashews and Swiss cheese.

(3) Folate/Folic Acid

What it does:

Folate is necessary for the production of new cells, including red blood cells. Folate deficiency remains a major cause of spinal-cord defects in newborns.

How much you need:

Many dietitians recommend taking a multivitamin with 400 mcg of folic acid; 1,000 mcg per day is the safe upper limit for folic acid.

Food sources of folate:

Rich sources of folate include liver, dried beans and peas, spinach and leafy greens, asparagus and fortified cereals.

(4) Vitamin D

What it does:

Early on, most of the concern focused on bones, since vitamin D, working along with calcium, helps build and maintain them.

How much you need:

Official recommendations now call for 200 IU for children and 600 IU for people over 71, with other groups falling somewhere between.

Food sources of vitamin D:

We rely on fortified milk and breakfast cereals to get most of our dietary vitamin D. Apart from a few kinds of fish, including herring and sardines, there aren't many natural food sources, which leaves supplements and direct sunlight.

(5) Vitamin C

What it does:

Researchers have long known that vitamin C is an essential building block of collagen, the structural material for bone, skin, blood vessels and other tissue.

How much you need:

The current recommended daily intake for men is 90 mg and for women it is 75 mg. The body can only absorb a maximum of about 400 milligrams a day.

Food Sources of Vitamin C:

Virtually everything in the produce section including oranges, green bell peppers, strawberries, broccoli, cantaloupe and tomatoes, turnip greens, sweet potatoes and okra.

(6) Magnesium

What it does:

Necessary for some of the body's most basic processes, magnesium triggers more than 300 biochemical reactions—most importantly the production of energy from the food we eat.

How much you need:

Around 300 mg/day (women) and 350 mg/day (men), with the upper limit for supplemental magnesium at 350 mg.

Food sources of magnesium:

The mineral is abundant in avocados, nuts and leafy greens including acorn squash, kiwi and almonds.

(7) Potassium

What it does:

Potassium is involved in almost every vital body process: maintaining blood pressure, heart and kidney function, muscle contraction, even digestion.

How much you need:

Surveys show that most Americans get less than half the recommended amounts of potassium, which is 4,700 milligrams (mg) daily for adults and teens.

Food sources of potassium:

Foods that are closest to their original states are best, so be sure to choose whole, unprocessed foods as often as possible, especially fruits and vegetables, low-fat dairy products, whole grains,

(8) Vitamin K

What it does:

Vitamin K is used by the body to produce an array of different proteins. Some of them are used to create factors that allow blood to coagulate—critical in stemming bleeding and allowing cuts and wounds to heal.

How much you need:

The current recommended daily intake of vitamin K is 90 micrograms for women and 120 for men. Luckily, vitamin K deficiency is extremely uncommon.

Food Sources of Vitamin K:

Kale, spinach, broccoli, asparagus, arugula, green leaf lettuce, soybean oil, canola oil, olive oil and tomatoes

(9) Chromium

What it does:

Chromium is required by the body for the process that turns food into usable energy, helping insulin prime cells to take up glucose.

How much you need:

Despite disappointing findings on chromium supplements and weight loss, the body still needs it. The daily recommended intake for adults is 50 to 200 mcg.

Food sources of chromium:

Best sources of chromium are whole-grain breads and cereals, meat, nuts, prunes, raisins, beer and wine.

(10) B12

What it does:

Vitamin B12 is used in making DNA, the building block of genes, and in maintaining healthy nerve and red blood cells.

How much you need:

2.4 micrograms a day for people 14 and older provides all the body needs—although some researchers have argued that a daily intake of 6 micrograms would ensure absorption.

Food sources of B12:

B12 is bound to protein, so foods like meat, fish, eggs and dairy products like yogurt and milk are the principal sources.

(11) Beta Carotene

What it does:

In the body, beta carotene is converted to vitamin A, a nutrient essential for healthy vision, immune function and cell growth. It also acts as an antioxidant that neutralizes free radicals.

How much you need:

There's no RDA for beta carotene.

Food Sources of Beta Carotene:

Eat plenty of dark green vegetables and orange vegetables and fruits (papaya, mango) weekly to meet your vitamin A needs and reap beta carotene's potential antioxidant benefits.