A fish diet benefits heart health in young women
“An ounce of prevention is worth a pound of cure.” For young women, that old adage may apply to eating fish. According to a new study, a fish diet might provide immediate cardiovascular benefits to young woman. The study was published online on December 5 in the journal Hypertension. Lead author Dr. Marin Ström and colleagues at the Statens Serum Institut (Copenhagen, Denmark) conducted a large prospective study to examine fish consumption among young women. It found that even moderate intake of fish, just once a week, can be cardioprotective. According to Dr. Ström, the findings are important for a number of reasons. They demonstrate that the benefits of a healthy lifestyle can be obtained at a relatively young age.
"We saw quite strong associations with cardiovascular diseases occurring in the study participants when they were in their late 30s," she noted, adding, "The biggest challenge in getting health messages like this across to younger populations is that usually the benefits may not be evident for 30 or 40 years, but our study shows that this is not the case." By demonstrating that the benefits of eating fish are immediate, the researchers believe it will be easier to convince people to make healthy choices.
The research, which is one of the first to be conducted on women of childbearing age, examines primary prevention, notes Dr. Ström. The majority of the previous studies on cardiovascular health were conducted on men, in the context of secondary prevention after a cardiovascular event. According to Dr. Ström, studying women separately is important because evidence exists that certain risk factors that can be influenced by fish consumption, such as triglyceride levels, "may have a more negative influence on cardiovascular risk in women than in men."
The researchers used the Danish National Birth Cohort to identify young women and examine whether a fish diet rich in omega-3 fatty acids might reduce cardiovascular risk, by linking to cardiovascular events, which were recorded in the Danish National Patients Registry. Almost 50 000 women (median age: 30) were interviewed in early pregnancy by telephone or questionnaire regarding how much and how often they ate fish and what types. In addition, they were also questioned about other lifestyle choices and family history. Women taking fish-oil capsules (less than 5% of the population) were excluded from the study because it was not possible to calculate the actual intake of n-3 fatty acids from this source, said Dr. Ström.
A total of 577 cardiovascular events occurred during the follow-up period (1996–2008; median eight years). Specifically, 328 events occurred due to hypertension (high blood pressure), 146 due to a cerebrovascular event (stroke), and 103 from ischemic heart disease (decreased blood supply to the heart muscle). Women who never or very rarely ate fish were found to have an almost 100% increase in cardiovascular disease risk compared with those who ate fish every week (corresponding to 10 grams of fish per day or higher). For women who consistently reported the same frequency of fish intake on three different occasions during a 30 week period, a threefold higher cardiovascular disease risk was found for women who never ate fish, compared with those eating fish every week.
The women in the study mainly ate cod, plaice, salmon, herring, and mackerel. Dr. Ström noted that the results were in accord with previous observational studies based on older women; those studies suggested that the potential cardiovascular benefits can be obtained with relatively moderate intake of fish even just a few of times per month. She stressed, however, that to obtain the greatest benefit from fish, it should be consumed as a main meal at least twice a week. She noted, "There are other health benefits that are obtained only at high intakes."
In regard to the risk/benefit of a fish diet for pregnant women (i.e., mercury content), Dr. Ström noted that species with high mercury contents, such as shark, "are not commonly consumed in Denmark." She noted that most developed nations have developed dietary guidelines for pregnant women, which advise that they should not eat predator fish in large amounts. She also said that some large studies have shown that the gains from the particular nutrients found in fish, such as long-chain n-3 polyunsaturated fatty acids and selenium, outweigh the risks from contaminants such as mercury in pregnant women. She said, "Fish is the most important dietary source for the fetus to obtain the long-chain fatty acids that we believe are necessary to ensure optimal brain development.” She added that a recent U.S. review determined that despite the risk of environmental contaminants with some fish types, the benefits of eating fish still outweigh the risks.