The blood pressure reducing benefits of salmon and fish oil were especially noticeable in people with initially low levels of docosahexanoic acid (DHA) in their cell membranes, according to findings published online ahead of print in Nutrition.
Over 300 young overweight individuals were followed for eight weeks by researchers from the University of Iceland, the University of Navarra, University College Cork, and the Portuguese National Research Institute on Agriculture and Fisheries Research in Lisbon.
Omega-3 has been identified as one of the super-nutrients taking the food and supplements industry by storm. Much of its healthy reputation that is seeping into consumer consciousness is based largely on evidence that it can aid cognitive function and may help protect the heart against cardiovascular disease.
Several intervention trials have reported positive benefits on blood pressure and cardiovascular disease using omega-3 fatty acids. Indeed, a meta-analysis of randomised, controlled trials showed significant decreases in both systolic and diastolic blood pressure with omega-3 doses in the region of two to three grams per day.
The new study, led by Prof. Inga Thorsdottir, from the University of Iceland, adds to this body of science, and reported that increasing fish oil or fatty fish intakes in people with low DHA levels in cell membranes may lead to greater blood pressure improvements.
High blood pressure (hypertension),defined as having a systolic and diastolic blood pressure (BP) greater than 140 and 90 mmHg, is a major risk factor for cardiovascular disease (CVD) - a disease that causes almost 50 per cent of deaths in Europe, and reported to cost the EU economy an estimated €169bn ($202bn) per year.
Study details
Prof Thorsdottir and her co-workers recruited 324 people aged between 20 and 40 with body mass indexes ranging from 27.5–32.5 kg/m2. The recruits, from Iceland, Spain, and Ireland, were subsequently randomly assigned to one of four energy-restricted diets: salmon, cod, fish oil capsules, or control (sunflower oil capsules and no seafood).
Both fish diets provided 150 grams if fish three times per week. Loders Crocklaan provided the fish oil supplements (1.3 g of omega-3 LC-PUFAs per day), which were composed of 22.7 per cent EPA and 15.4 per cent DHA.
Corresponding author, Alsons Ramel, PhD, told NutraIngredients.com that the specific fatty acid composition of the salmon (150 grams three times per week, 2.1 g of omega-3 LC-PUFAs per day) was measured to be 1,200 mg of EPA per 100 grams of salmon, 2,100 mg of DHA per 100 grams of salmon, and about 470 milligrams of DPA per 100 grams of salmon. The cod diet provided 150 grams of fish three times per week, and equated to a daily dose of 0.3 g of omega-3 LC-PUFAs per day.
At the end of the intervention period, Prof Thorsdottir and her co-workers noted that all participants experienced an average weight loss of 5.2 kilograms. The general study population also experienced reductions in both systolic and diastolic blood pressure of 4.4 and 4.1 ± 7.4 mmHg, respectively.
Similar blood pressure reductions were observed in the salmon and fish oil groups, and significantly greater than those observed in the cod group. However, no significant difference was observed between the fish oil and salmon groups, and the control.
“This finding was unexpected, because we expected the endpoint DBP of the control group to be closer to that of the cod group, because both diets provided no or only small amounts of u-3 LC-PUFAs,” wrote the researchers. “According to the food records, dietary intake of relevant nutrients (calcium, potassium, sodium) was not significantly different among groups, and, because the control group received capsules daily, a certain placebo effect cannot be excluded.”
“A lower DHA content in erythrocyte membrane at baseline, which might identify infrequent fish eaters, is associated with a greater DBP reduction in the course of an eight-week dietary intervention providing fatty seafood,” they concluded.
Source: Nutrition Published online ahead of print, 31 May 2009, doi:“Moderate consumption of fatty fish reduces diastolic blood pressure in overweight and obese European young adults during energy restriction” Authors: A. Ramel, J.A. Martinez, M. Kiely, N.M. Bandarra, I. Thorsdottir