INTRODUCTION — Nonpharmacologic (ie, lifestyle) interventions are indicated in nearly all patients with hypertension; in some patients, lifestyle intervention is the only approach needed and antihypertensive medication is unnecessary (see "Overview of hypertension in adults", section on 'Nonpharmacologic therapy'). Dietary modification is an important component of nonpharmacologic therapy in most patients. A variety of dietary modifications are beneficial in the treatment of hypertension, including reduction of sodium intake, moderation of alcohol, weight loss in patients with overweight or obesity, and a diet rich in fruits, vegetables, legumes, and low-fat dairy products and low in snacks, sweets, meat, and saturated fat. Individual dietary factors may also reduce blood pressure (BP) [1].
Nondietary modalities of lifestyle modification should also be considered, including cessation of smoking and institution of an aerobic exercise regimen. (See "Smoking and hypertension" and "Exercise in the treatment and prevention of hypertension".)
Most of the studies on nonpharmacologic therapy evaluated only a single factor to prove its efficacy (eg, weight reduction without sodium restriction). In making recommendations to the individual patient, however, the clinician will try to modify all of the factors that may be contributing to the elevation in BP, although it is uncertain if the effects of different modifications are additive.
In those with elevated BP or stage 1 hypertension, lifestyle changes may control the BP adequately [1]. However, in those with either higher BP or additional risk (eg, diabetes or chronic kidney disease), drug therapies should first be used to more quickly and effectively control the BP. Once BP is well controlled, lifestyle changes should be strongly advised. If these are successfully achieved, reduction of medications may be possible.
This topic will review the effect of comprehensive dietary modification, as well as the effects of individual dietary interventions on BP.
OUR APPROACH: COMPREHENSIVE DIETARY MODIFICATION — Many studies have examined the effects of comprehensive dietary modification, in which multiple dietary factors are modified, on blood pressure [2,3]. Most comprehensive dietary modification studies have tested dietary patterns that emphasize plant-based foods and de-emphasize animal-based foods. Among these, the two dietary patterns that have the greatest impact on blood pressure lowering and that are supported by the strongest data are the Dietary Approaches to Stop Hypertension (DASH) diet (see 'Dietary Approaches to Stop Hypertension (DASH) diet' below) and a lacto-ovo vegetarian diet (which incorporates eggs and dairy products as protein sources). In a meta-analysis of 41 trials, the DASH diet and a lacto-ovo vegetarian diet reduced systolic blood pressure by 5.5 mmHg, an effect that was larger than the effects of a Mediterranean diet, a fruit-and-vegetable diet, a high-fiber diet, and a vegan diet [2].
Referral to a nutritionist for dietary education and support may help patients attain appropriate dietary modification.
Dietary Approaches to Stop Hypertension (DASH) diet — Unless the patient is a lacto-ovo vegetarian, we suggest dietary modification according to the DASH dietary pattern, which is described below. In lacto-ovo vegetarians, we suggest limiting snacks and sweets, if necessary. In patients with hypertension, strict adherence to the DASH diet has an effect on blood pressure that is similar to that of an antihypertensive drug.
●Dietary Approaches to Stop Hypertension trial – Most early dietary studies in patients with hypertension focused on reduction in sodium intake. A different approach was evaluated in the Dietary Approaches to Stop Hypertension (DASH) trial [4]. Rather than evaluating sodium intake or weight loss, DASH randomly assigned 459 patients with BPs of less than 160/80 to 95 mmHg to one of three diets:
•A control diet low in fruits, vegetables, and legumes and high in snacks, sweets, meats, and saturated fat.
•A diet rich in fruits, vegetables, legumes and low in snacks and sweets.
•A combination diet rich in fruits, vegetables, legumes, and low-fat dairy products and low in snacks, sweets, meats, and saturated and total fat (this combination diet is called the "DASH diet"). The DASH diet consists of four to five servings of fruit, four to five servings of vegetables, two to three servings of low-fat dairy per day, and <25 percent fat.
The following observations were noted in which the BP reductions were expressed in relation to the fall in BP seen with the control diet:
•The fruits and vegetables diet reduced the BP by 2.8/1.1 mmHg, and the combination diet reduced the BP by 5.5/3.0.
•These effects were more pronounced in patients with hypertension. With the combination diet, for example, the BP fell 11.4/5.5 mmHg in hypertensives versus 3.5/2.1 mmHg in the normotensives.
•The antihypertensive effects were maximal by the end of week 2 with any of the diets and were then maintained for eight weeks.
●Low-sodium DASH – The combination of a low-sodium and DASH diet results in the most significant benefit. A second DASH trial evaluated the effect of varying sodium intake in combination with consuming the DASH diet described above [5]. In this study, 412 participants were randomly assigned to a DASH or control diet and, within each diet, ate foods with three levels of sodium content (high [3.5 g], intermediate [2.3 g], and low [1.2 g]) for 30 days each. The following results were reported:
•At all three levels of sodium intake in the DASH and control diets, the DASH diet resulted in lower systolic and diastolic BP compared with control. The impact of the DASH diet on relative BP reduction was more pronounced in participants with higher sodium intakes. At high, intermediate, and low levels of sodium intake, the DASH diet systolic pressure was 5.9, 5, and 2.2 mmHg lower than the control diet, respectively. Corresponding reductions in diastolic pressure were 2.9, 2.5, and 1 mmHg.
•With either diet, lowering the sodium intake reduced BP levels, an effect observed among those with and without hypertension and among different races and sex.
•When different phases of diet were compared, the most significant decrease in BP was observed between the high-sodium control diet and low-sodium DASH diets as a comparative overall reduction of 8.9 and 4.5 mmHg in systolic and diastolic BPs, respectively, was noted with the low-sodium DASH diet. This benefit was even more significant among hypertensive individuals. The mean fall in systolic BP was 11.5 mmHg.
●PREMIER trial – The PREMIER trial was designed to assess the additive BP effects of two different behavioral interventions [6]. In this study, 810 patients with above optimal BP (120 to 159 mmHg systolic pressure and/or 80 to 95 mmHg diastolic pressure) were randomly assigned to one of three groups: 1) "established behavioral intervention" (eg, weight loss, physical activity, and limitations in sodium and alcohol intake); 2) the DASH diet plus "established behavioral intervention"; and 3) one-time advice only. Unlike the original DASH study, the subjects prepared their own food. To assess the effects on BP of the interventions, the effect of advice only (6.6/3.8 mmHg decrease) was subtracted from the BP change in the intervention groups.
At six months, the DASH diet plus behavioral intervention produced a small additional decrease in BP versus that observed with behavioral intervention alone (4.3/2.6 mmHg and 3.7/1.7 mmHg, respectively). The prevalence of mild hypertension at study end was significantly less in the two intervention groups (12 and 17 percent in DASH plus established and established group, respectively) than in the advice-only arm (26 percent). At 18-month follow-up, the prevalence of hypertension had increased in all three groups, but remained lowest in the two intervention groups (22 and 24 percent in DASH plus established and established group, respectively, versus 32 percent in the advice only) [7]. (See 'Prevention' below.)
Overall, the absolute effects on BP of DASH plus those of behavioral intervention were not additive. Possible reasons for this less than expected effect of the DASH diet included the requirement that the subjects prepared their own food, so there was less rigorous adherence to the diet than in the other DASH studies, where all the food was provided; a large BP decrease in the advice-only control group; and a possible similar physiologic mechanism for BP lowering for both interventions [8].
In addition to the three trials above, the DASH diet lowered blood pressure in other studies [9].
Increased potassium intake and decreased sodium intake — Adherence to the DASH diet will increase daily potassium intake. However, increasing potassium intake and lowering sodium intake without comprehensive dietary modification (such as with a potassium-rich salt substitute) also can lower blood pressure.
Discussions of sodium and potassium intake and blood pressure are presented separately. (See "Salt intake and hypertension" and "Potassium and hypertension".)
OTHER DIETARY INTERVENTIONS — Other dietary interventions, such as supplementation with calcium, magnesium, or fish oil, appear to induce small and less predictable reductions in BP in most patients [10-15].
●Magnesium – Higher magnesium intake has been associated with lower BP [10,13].
●Fish oil – High-dose, but not low-dose, fish oil supplements may reduce systemic BP, although the effect appears to be modest [11,15-19]. The effect of fish oil supplementation on BP and other cardiovascular risk factors is presented separately. (See "Fish oil: Physiologic effects and administration", section on 'Potential effects on cardiovascular and metabolic systems' and "Fish oil: Physiologic effects and administration", section on 'System effects'.)
●Calcium – Although there appears to be an inverse relation between dietary calcium intake and BP in observational studies [20], the effect of calcium supplementation on BP is uncertain [12]. This was illustrated in a meta-analysis including 13 trials of eight weeks or longer in duration, which found that calcium supplementation modestly reduced systolic but not diastolic BP (by 2.5 mmHg); however, all but one trial were low quality [12].
The effect of supplemental calcium on BP is too small to recommend the use of calcium supplements for the therapy or prevention of hypertension. Moreover, in a community-based, prospective, longitudinal cohort study, high intake of calcium was associated with higher death rates from all causes and cardiovascular disease [21].
●High fiber – A higher intake of dietary fiber is associated with decreased systemic pressures [22]. Multiple meta-analyses have shown benefits with dietary fiber intake on BP [22-25]. As an example, a 2005 meta-analysis of 24 randomized, placebo-controlled trials published between 1966 and 2003 on the effects of fiber supplementation found an average fall of 1.2/1.3 mmHg with fiber intake (average dose of 11.5 g/day) [22]. More significant reductions were observed in older (greater than 40 years) and hypertensive individuals.
●Protein intake – Replacing carbohydrate intake with soy (vegetable) or dairy protein may reduce BP [26-31]. As an example, one study randomly assigned 302 Chinese subjects with untreated hypertension (systolic BP between 130 to 159 mmHg) to soybean protein or carbohydrate complex control [28]. After 12 weeks, systolic and diastolic BPs were 4.3 and 2.8 mmHg lower among those taking the protein supplement, compared with the control group. There was a greater effect among those with hypertension at baseline (BP >140/90 mmHg).
●Folate – An inverse association of folate intake with BP or hypertension has been shown in three large, prospective, cohort studies [32,33], as well as in several randomized trials [34-36]. In a meta-analysis of 12 randomized trials, supplemental folic acid (5 mg/day or more) significantly reduced systolic, but not diastolic, BP by 2.0 mmHg as compared with placebo [36].
●Flavonoids – The beneficial effect of fruits and vegetables on BP may be due in part to an increased intake of polyphenols (eg, flavonoids). Significant sources of these compounds in Western countries include tea and cocoa products. The effect of cocoa on BP was evaluated in a 2012 Cochrane meta-analysis of 35 studies consisting of 1804 subjects [37]. At a median duration of intake of 4.4 weeks, flavanol-rich cocoa products significantly reduced both systolic and diastolic pressure compared with low-flavanol-containing cocoa powder or flavanol-free interventions (mean reduction, 1.8/1.8 mmHg). A discussion of BP and tea ingestion is presented separately. (See "Cardiovascular effects of caffeine and caffeinated beverages", section on 'Blood pressure'.)
PREVENTION — Dietary and lifestyle modifications have been evaluated in a number of studies for the prevention rather than treatment of hypertension [17,38-44]. As illustrated by the following observations, the optimal effect on blood pressure (BP) is achieved with correction of multiple contributors to hypertension, including salt intake, obesity, and excess alcohol intake. (See "Salt intake and hypertension" and "Overweight, obesity, and weight reduction in hypertension" and "Cardiovascular benefits and risks of moderate alcohol consumption", section on 'Hypertension'.)
The relative efficacy of such interventions can be illustrated by the results of two randomized trials and a large observational study:
●The Trials of Hypertension Prevention, phase II randomized 2382 individuals (aged 30 to 54 years) with a BP <140/83-89 who were 110 to 165 percent of ideal body weight [38]. The patients were randomly assigned to usual care, salt restriction, weight reduction, or both. Sodium restriction was associated with a 50 and 40 mEq decline in sodium excretion at 6 and 36 months, respectively. Sodium restriction plus weight loss was associated with a decrease in weight from baseline of 4 and 2 kg at 6 and 36 months, respectively. Compared with usual care, the BP fell at six months by 3.7/2.7 with weight loss, 2.9/1.6 with salt restriction, and 4.0/2.0 with combined therapy. These effects were attenuated at 36 months, but, at 48 months, the likelihood of progressing to hypertension was reduced with nonpharmacologic therapy (relative risk 0.78 to 0.82).
●The TONE trial evaluated 975 older people (aged 60 to 80 years) who had a BP <145/<85 mmHg on one antihypertensive medication; 585 of whom had obesity [39]. The patients were randomly assigned to usual care or to salt restriction, weight loss (in patients with obesity), or both. Those assigned to salt restriction had a 40 mEq/day decrease in sodium excretion, while, in patients with obesity, a regimen of diminished caloric intake and increased physical activity was associated with a persistent weight loss of 4 to 5 kg; these parameters were unchanged in the usual-care group. After three months of intervention, withdrawal of the antihypertensive drug was attempted.
The primary endpoint was a diagnosis of high BP at one or more follow-up visits, treatment with antihypertensive drugs, or a cardiovascular event. The reduction in BP compared with usual care was 2.6/1.1 mmHg with salt restriction, 3.2/0.3 mmHg with weight loss, and 4.5/2.6 mmHg with combined therapy. The primary endpoint at 30 months occurred significantly less often with salt restriction (62 versus 76 percent with usual care), weight reduction in subjects with obesity (61 versus 74 percent), and combined salt restriction and weight reduction in subjects with obesity (56 versus 84 percent).
●The importance of risk factors for primary hypertension (formerly called "essential" hypertension) in women was evaluated in a prospective cohort study of 83,882 adult women from the second Nurses' Health Study who did not have a history of hypertension, cardiovascular disease, or diabetes [40]. Six lifestyle and dietary factors were independently associated with a lower risk of developing hypertension during 14 years of follow-up: body mass index of less than 25 kg/m2, a daily mean of 30 minutes of vigorous exercise, adherence to the Dietary Approaches to Stop Hypertension (DASH) diet, modest alcohol intake, infrequent use of nonnarcotic analgesics, and intake of 400 mcg/day or more of folate [40]. The presence of all six factors was associated with a marked decrease in the risk for hypertension (hazard ratio 0.22, 95% CI 0.10-0.51).
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Hypertension in adults".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Controlling your blood pressure through lifestyle (The Basics)")
●Beyond the Basics topic (see "Patient education: High blood pressure, diet, and weight (Beyond the Basics)")
SUMMARY
●Diet and hypertension – Diet likely plays an important role in many susceptible patients in the genesis and maintenance of hypertension. (See 'Our approach: Comprehensive dietary modification' above.)
●DASH diet to lower blood pressure – A diet that is rich in fruits, vegetables, legumes, and low-fat dairy products and low in snacks, sweets, and meats (such as the Dietary Approaches to Stop Hypertension [DASH] diet) can lower blood pressure. In patients with hypertension, strict adherence to the DASH diet has an effect on blood pressure that is similar to that of an antihypertensive drug. The combination of a low-sodium and DASH diet results in the most significant benefit. (See 'Dietary Approaches to Stop Hypertension (DASH) diet' above.)
●Increased potassium intake and decreased sodium intake – Adherence to the DASH diet will increase daily potassium intake. However, increasing potassium intake and lowering sodium intake without comprehensive dietary modification (such as with a potassium-rich salt substitute) also can lower blood pressure. (See "Salt intake and hypertension" and "Potassium and hypertension".)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Norman M Kaplan, MD, who contributed to an earlier version of this topic review.
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