Applied nutritional investigationModerate consumption of fatty fish reduces diastolic blood pressure in overweight and obese European young adults during energy restriction
Introduction
Hypertension is one of the causes of cardiovascular disease [1]. Diet plays an important role in the etiology of hypertension, because obesity and nutrient intake are known to affect blood pressure (BP). The BP-lowering properties of ω-3 long-chain polyunsaturated fatty acids (ω-3 LC-PUFA) from fish oil supplements have been thoroughly investigated and confirmed [2], [3], [4], [5], with commonly used doses of 4–5 g of ω-3 LC-PUFAs per day leading to clinically significant reductions in BP. The largest effects are achieved in elderly hypertensives [4]. Several biological mechanisms have been suggested to explain the health benefits of ω-3 LC-PUFAs on BP, e.g., changes in phospholipid composition, platelet aggregation, and vasodilatation [6], [7], [8], [9], [10], [11].
Without the use of seafood supplements (fish oil or marine algae), a ω-3 LC-PUFAs intake of 4–5 g/d can hardly be achieved, even if one consumes a daily fish meal. There are relatively few dietary intervention trials that have investigated the effects of daily fish consumption (in contrast to fish oil ingestion) on BP, and some [12], [13] but not all [14], [15], [16] have found BP reduction by fatty fish consumption. Not daily, but still frequent fatty fish consumption, e.g., three times a week, usually provides a daily amount of 1–1.5 g of ω-3 LC-PUFAs and might be sustained easier by less committed seafood eaters than a daily fish meal. It is an important question whether such a dietary regimen can improve BP.
In the present analysis, which was a part of the SEAFOODplus YOUNG study, we investigated the effects of regular fatty fish consumption (salmon three times per week) in comparison with lean fish (cod three times per week), fish oil (daily) and a control without seafood, in combination with energy restriction, on BP in young overweight and obese adults. The reason for also investigating lean fish, which does not provide high amounts of ω-3 LC-PUFAs, is that there is some preliminary evidence from animal studies suggesting that fish protein might also have BP-lowering effects [17], [18]. We conducted a randomized, controlled dietary intervention trial in young overweight and obese, normo- and hypertensive individuals from three European countries. In terms of prevention, young adulthood might be a very critical time, with its changes in diet and physical activity linked with hypertension [19], [20]. Results from the SEAFOODplus YOUNG study, e.g., on weight loss, have been published elsewhere [21].
Section snippets
Subjects
A total of 324 overweight individuals (138 men and 186 women) were included in the SEAFOODplus YOUNG study (www.seafoodplus.org) through advertisements, 140 from Iceland, 120 from Spain, and 64 from Ireland. All subjects were screened for inclusion and exclusion criteria. The inclusion criteria were a body mass index ranging from 27.5 to 32.5 kg/m2, age 20–40 y, and waist circumferences ≥94 cm and ≥80 cm for men and women, respectively. Exclusion criteria were weight change (±3 kg) due to a
Results
The participants' baseline values are listed in Table 1. Of the male participants, 55.8% had hypertension, but only 15.6% of female participants did. Baseline docosahexaenoic acid (DHA) content in erythrocytes correlated with baseline DBP (ρ = −0.118, P = 0.050) and with frequency of fish consumption (ρ = 0.272, P < 0.001).
During the intervention (Table 2) the intakes of energy, carbohydrates, protein, fat, saturated fat, calcium, sodium, and potassium decreased significantly, with the highest
Discussion
In this study we investigated the effects of different diets on BP reduction during an 8-wk weight-loss diet in young overweight and obese European adults. Subjects in the four groups received salmon (fatty fish), cod (lean fish), fish oil capsules, or placebo capsules, but otherwise the same percentage energy restriction, and were recruited to diets prescribing identical macronutrient composition. During these 8 wk, mean body weight, SBP, and DBP decreased significantly in the participants.
Conclusions
Salmon consumption decreases DBP similar to fish oil consumption and more than lean fish consumption during an 8-wk diet in young overweight individuals. Lower DHA content in erythrocyte membrane at baseline, which might indentify infrequent fish eaters, is associated with greater DBP reduction during an 8-wk dietary intervention providing seafood.
Acknowledgments
Thanks are due to the European Union Commission for financial support and to the volunteers participating in the study.
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The YOUNG study is part of the SEAFOODplus Integrated Project, which is funded by the European Commission through the 6th Framework Programme Contract FOOD-CT-2004-506359. The trial is registered at the U.S. National Library of Medicine (NCT00315770).