Dietary intervention for hypertension requires low-fat foods, but the type of fat is the most important guiding factor, as even the Mediterranean diet is loaded with fish, a source of both protein and essential fatty acids (EFAs).
Higher consumption of fish, salad and cereals in adolescence has a positive effect on diastolic blood pressure and establishes a front against chronic disease, according to Australian researchers.1 Another Australian study found higher consumption of fish had vascular protective effects.2 Similarly, Italian research noted hypertensive adults who made a long-term dietary change to consume more fish and vegetables had better blood pressure management.3 A 2007 research review reported consumption of fish oil and its omega-3 EFAs can have a small but significant benefit to blood pressure, particularly among adults with hypertension.4 Epidemiological data from the aforementioned INTERMAP trial indicated an inverse relationship between total omega-3 intake from food and diastolic and systolic blood pressures, with the greatest impact from long-chain omega-3 intake from fish.5
Many hypotensive diets place tough limitations on meat intake, relative to American gastronomy. Offering flexibility on protein intake may help improve adherence to DASH, Mediterranean and similar diets, according to researchers at Brigham and Women’s Hospital, Boston.6 They found slightly raising the level of healthy unsaturated fats and protein in these diets achieves similar blood pressure benefits, but make it easier to follow the diets long term.
As in the case of calcium, dairy products may be limited in blood pressure-lowering diets, but the peptides in milk and whey may help manage hypertension. Such peptides may inhibit vasoconstrictor enzymes such as angiotensin-1-convering enzyme (ACE), and positively impact vasodilation.7 Specifically, tetrapeptides from milk protein (alpha-lactorphin and beta-lactoglobulin) administered to spontaneously hypertensive rats improved vascular relaxation, influencing both endothelial function and endothelium-independent relaxation.8 A 2006 trial conducted at the University of Minnesota, Minneapolis concluded six weeks of whey-derived peptide supplementation in human subjects resulted in significant reductions in systolic and diastolic blood pressure, in addition to improvements in low-density lipoprotein (LDL) cholesterol and inflammatory markers.9 Long-term intake of the ACE-inhibiting peptides isoleucine-proline-proline (IPP) and valine-proline-proline (VPP) slows the development of hypertension.10 A 2008 meta-analysis out of Norway confirmed peptides from such protein sources significantly lower both systolic and diastolic pressure, with the majority of studies using IPP and VPP.11 Then in 2009, DSM published safety research on its tensVida™ milk protein hydrolysate containing the lactotripeptide IPP, showing the ingredient is safe for use as intended after passing a 90-day repeated-dose oral toxicity study in rats, as well as several genotoxicity tests.12 Still other research suggests opioid receptors may be involved in the actions of tetrapeptides on diastolic and systolic blood pressure.13
Despite the potential for dairy-based peptides to manage hypertension, soy protein maintains the plant-focus of hypotensive diets and still offers improvement to blood pressure levels, in addition to its other well-known heart-health benefits.
Analysis of data from the Shanghai Women’s Health Study concluded long-term consumption of soy protein was inversely related to both systolic and diastolic pressure, with the association growing stronger with age.14 Also, substituting soy nuts for non-soy protein could significantly reduce blood pressure in both normotensive and hypertensive women, according to research from Beth Israel Deaconess Medical Center, Boston, which attributed the benefit to improved endothelial function and reduction in inflammation.15 Likewise, adding 10 g/kg/d of soy powder (31 percent isoflavones) to a high-fat diet can decrease oxidative damage, inhibit increases in blood pressure and influence NO production for endothelial benefit.16 Of soy isoflavones, genistein has improved aortic endothelial-derived NO, alleviating hypertension in the rats.17
Fermented soy, called natto, contains ACE-inhibiting substances that have antihypertensive effects.18 Natto has also been shown to suppress intimal thickening in the arteries. Nattokinase, may contribute to blood-pressure management by breaking up blood fibrin, a protein involved in clotting. Proprietary research from Japan Bio-Science Laboratories on its NSK-SD® nattokinase ingredient attributed vascular benefits to the enzyme's effects on blood coagulation, blood flow and hypertension in adults with untreated high blood pressure. In a 2008 study from Yonsei University, Seoul, Korea, untreated hypertensive adults (systolic=130-159 mmHg) who took nattokinase (2,000 fibrin-degrading units/capsule) for eight weeks had significant reduction in systolic (-5.5 mmHg) and diastolic (-2.8 mmHg) blood pressure.19
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