A study within a study

The new report from the Framingham Osteoporosis Study, published in the American Journal of Clinical Nutrition, included 854 people, ages 67 to 93, who had originally enrolled in the Framingham Heart Study, a large ongoing study that began in 1948. Hip bone mineral density measurements were taken at the beginning and end of this four-year sub-study, and eating habits were evaluated using diet questionnaires.

Eating dark fish may lead to less bone loss

The study found a few interesting links between diet and bone density:

• Men and women who ate three or more servings of dark fish per week experienced less bone loss than men and women who ate less dark fish. Dark fish includes mackerel, salmon, sardines, bluefish, and swordfish.
• In men, but not women, tuna intake was also linked to bone density preservation.
• Arachidonic acid, a major fatty acid found in animal fats, appeared to prevent bone mineral density loss in women with high fish intake, and to increase loss in men with low fish intake, suggesting a complex interaction between fish and animal fats.

“Taken together, these results support the hypothesis of a protective effect of fish intake, particularly dark fish intake, on bone mineral density in the elderly,” said study co-author Dr. Katherine Tucker of Northeastern University in Boston.

Picking the best fish

These findings add to a growing body of research showing that dietary omega-3 fish fats could play an important role in preventing bone loss as we age. Here are some things to consider as you add extra fish portions to your regular diet:

• Pick wild pink when it comes to salmon. Wild pink salmon, rich in healthy omega-3 fats, are smaller and shorter-lived than other types of salmon, so have less time to accumulate toxins like mercury and PCBs.
• Choose sardines over swordfish. Like mackerel, sardines are high in omega-3 fats and low in toxins, while swordfish may have plenty of the healthy fats but with a heavier toxin load.
• Choose tuna carefully. Albacore tuna from the US and Canada have lots of omega-3 fats and are relatively low in toxins, but in general, tinned white albacore tuna should be eaten sparingly.

You can learn more about health and safety issues around fish consumption from the Environmental defence Fund (www.edf.org/page.cfm?tagID=1521) and Physicians for Social Responsibility (www.psr.org/resources/healthy-fish-healthy.html).

(Am J Clin Nutr 2011;93:1142–51)