Last week's breaking nutrition news -- that eating fatty fish once a week lowers heart disease risks -- arrived hard on the heels of last month's study that said eating fish didn't lower heart disease risks.
Confused? There's no need to be. Evolving research shows fish is heart-healthy food, and the "scientific process" is working just the way it's supposed to.
The fish-heart disease connection is being explored because large population studies show countries in which people eat a lot of fish have low heart disease rates. So researchers want to know if this is coincidence, or if fish has a protective effect. That's not easy to figure out.
When you're working with laboratory rats, you can control their genetic background, their exercise levels, every mouthful of food they eat, all the fluids they drink, and whether or not they smoke.
Rats have a short life cycle, so it's relatively easy to study several generations. People studies take longer and are more expensive.
What's emerging in the fish story is that it's the fat, not the flesh of the fish, that provides the benefits. This most recent study shows higher-fat fish have the greatest protective effect, and that's right in line with the body of information that's been evolving over time. This seems to contradict our current low-fat focus, but the details make the difference.
The fat we've been fighting is the saturated kind, found primarily in animal products such as whole-fat milk, cheese and yogurt, as well as in meat and poultry products. Diets high in saturated fat tend to cause blood cholesterol levels to rise, then be deposited on arterial walls.
This buildup narrows arteries, creating a trap for small floating blood clots that can get stuck, blocking blood flow. If this happens in your brain, it's called a stroke. If it happens in your coronary arteries, it's a heart attack.
Fish fat is different. It contains polyunsaturated omega-3 fatty acids, which start a chain of events responsible for decreasing the sticking quality of blood-clotting platelets. Diets high in omega-3 fatty acids tend to produce fewer blood clots, reducing the likelihood one will get stuck in a narrowed artery.
This new study adds still another puzzle piece. Apparently the omega-3 fatty acids also get incorporated into red blood cell membranes themselves, changing the way they function. Exactly how is yet to be uncovered. (And that's the scientific process -- for every question answered, dozens more arise.)
When it comes to balancing out total fat in your diet, this study falls in line, again, with current guidelines. While the focus is on higher-fat fish, the portions are small. One 3-ounce portion each week can make the difference. A 3-ounce portion of salmon, for instance, is about the size of the palm of your hand, much smaller than the usual restaurant portion.
Higher-fat fish include salmon, anchovies, herring, mackerel and sardines. The study noted that doubling the portion of lower-fat fish (eating two 3-ounce portions of albacore tuna each week) is also effective.
Fat-free cooking techniques work especially well with high-fat fish, producing moist, delicious dishes. You can grill salmon, using a fat-free salad dressing as a basting sauce. Or use canned salmon to replace butter on baked potatoes. (If you eat the bones, you get an extra dose of calcium.)
Colleen Pierre, a registered dietitian, is the nutrition consultant at the Union Memorial Sports Medicine Center and Vanderhorst & Associates in Baltimore.