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808 PA R T V / Health Promotion and Disease Prevention
(defined as an increased waist-to-hip ratio of more than 0.85 in with HTN should exercise moderately for a minimum of 30 min-
women and 0.95 in men) and the development of HTN, diabetes, utes almost every day of the week. 7
dyslipidemia, and increased CHD mortality. 83–87 Studies in Sodium Restriction. In general, as the amount of dietary salt
Framingham, Massachusetts and Evans County, Georgia revealed (sodium chloride) intake rises, so does BP. 79 The most persuasive
that overweight people have from two to three times the risk for evidence about the effects of salt on BP comes from rigorously con-
HTN compared with persons who are not overweight. 17,88 The trolled, dose–response trials. 124–126 Each of these three trials tested
exact mechanism by which obesity contributes to HTN is unclear. at least three sodium levels, and each documented statistically sig-
However, the influence of weight may be related to alterations in nificant, direct, progressive dose–response relationships. The
cardiovascular, endocrine, and metabolic factors caused by obesity. largest of the dose–response trials, the Dietary Approaches to Stop
These alterations include increased cardiac output, increased blood Hypertension (DASH)-Sodium trial, tested the effects of three dif-
volume, and sodium retention. Research now suggests that adipose ferent levels of sodium intake separately in two distinct diets: the
tissue acts as a major endocrine organ, secreting bioactive substances DASH diet and a control diet more typical of what Americans eat.
which may induce metabolic disorders, such as hyperinsulinemia, The three sodium levels (lower, intermediate, and higher) pro-
insulin resistance, decreased carbohydrate tolerance, and decreased vided approximate sodium intakes of 1.5, 2.5, and 3.3 g, respec-
insulin sensitivity. 89–91 Alterations in endothelial function have also tively. The BP response to sodium reduction, while direct and
been demonstrated in persons who are overweight. 90,92 progressive, was nonlinear. Specifically, decreasing sodium intake
Weight loss has consistently been demonstrated to reduce BP by 0.9 g/day (40 mmol/day) caused a greater lowering of BP when
more effectively than any other lifestyle measure. 74–76,93–98 The the starting sodium intake was 100 mmol/day than when it was
94
study by Langford et al. of participants whose BP had been con- above this level. In subgroup analyses of the DASH-Sodium trial
trolled with medications for 5 years found that an average weight reduced sodium intake significantly lowered BP in each of the ma-
loss of 10 lb prevented 60% of the overweight subjects from having jor subgroups studied (i.e., men, women, Blacks, and non-
to return to taking medications. In addition, weight loss has been Blacks). 127,128 The effects of sodium reduction on BP tend to be
found to complement pharmacologic management of mild-high greater in Blacks; middle-aged and older persons; and individuals
BP. 99,100 In recent meta-analysis of 25 randomized control trials, with HTN, diabetes, or CKD. 79 In addition, clinical trials have
which included trials based on weight reduction through energy re- documented that reduced sodium intake can lower BP in the set-
striction, increased physical activity, or both, average reductions of ting of antihypertensive medication and facilitate HTN control
4.4/3.6 mm Hg for SBP and DBP, respectively were reported for a and is associated with a reduced risk of atherosclerotic cardiovas-
98
5-kg weight loss. A dose–response relationship was observed with cular events and congestive heart failure. 79,129
greater weight loss resulting in greater BP reduction. JNC 7 recommends a goal sodium intake of 100 mmol/day,
Counseling a hypertensive, overweight patient about weight which is equivalent to approximately 6 g of sodium chloride or
reduction is important, both as a preventive measure as well as an 2.4 g of sodium per day. In many of the clinical trials of sodium
7
independent or complementary treatment for high BP. The chal- reduction, the goal levels of sodium intake were even lower than
lenge for both clinicians and patients is supporting maintenance this recommended goal. To reduce salt intake, individuals should
of weight loss, because longitudinal studies have shown that sub- choose foods low in salt and limit the amount of salt added to
jects who lose weight initially tend to gain back the weight over food. However, because 75% of consumed salt comes from
time. 76
processed foods, any meaningful strategy to reduce salt intake
must involve the efforts of food manufacturers and restaurants. It
Physical Activity. A sedentary lifestyle is one of the risk fac- may help patients to know that it takes 8 to 12 weeks to adjust
tors for HTN. 80,101–105 There is increasing evidence showing in- one’s sense of taste to a lower intake of sodium. 130
activity in American adults. For example, in 2005 less than half of
80
the U.S. adults met recommendations for physical activity. The Diet High in Fruits and Vegetables. The DASH study ex-
results of four meta-analyses on the effect of physical activity on amined the effects of an 8-week dietary intervention on BP in
HTN concluded that aerobic training does reduce BP. 106–109 The normotensive and hypertensive subjects. 77 The DASH diet em-
data indicate that physical fitness training had a graded influence phasized fruits, vegetables, and low-fat dairy products; included
on BP from a small influence on normotensive individuals to a whole grains, poultry, fish, and nuts; and was reduced in fats, red
larger impact on those with HTN. Other analyses indicate that meat, sweets, and sugar-containing beverages. Accordingly, it was
persons who are physically active experience reduced cardiovascu- rich in potassium, magnesium, calcium, and fiber and was re-
lar and all-cause mortality rates. 110–122 duced in total fat, saturated fat, and cholesterol; it also was slightly
Physical activity is known to have a variety of metabolic and increased in protein. In the 133 hypertensive subjects, the investi-
other effects that may partially explain its beneficial effects on BP. gators found that adherence to a diet rich in fruits, vegetables, and
These include reduction in resting cardiac output and peripheral low-fat dairy products and low in saturated and total fat resulted
vascular resistance, a humoral mechanism contributing to reduc- in a marked decline in both SBP and DBP. Compared with nor-
tion of the activity of the rennin–angiotensin–aldosterone system motensive control subjects, those subjects with an SBP between
and sympathetic nervous system activity, and increase in 140 and 160 mm Hg and/or a DBP between 90 and 95 mm Hg
prostaglandins with vasodilator effect. 80,109 Importantly, an effect had decreases in BP of 11.4/ 5.5 mm Hg. There was no signif-
of physical exercise on TOD has also been demonstrated. Two stud- icant change in weight during the study in any of the study groups.
ies of 18 persons with HTN and LVH found that after 24 to The DASH diet included 8 to 10 servings per day of fruits and
32 weeks of exercising at least three times per week, the participants vegetables and 2.7 servings of low-fat dairy products. Subsequent
had significant decreases in indices of LVH. 123 A confounding fac- clinical trials based on the DASH diets have shown that (1) adding
tor in many of these studies is that physical activity intervention is salt reduction results in a significantly greater decrease in SBP and
t
often combined with weight loss. It is recommended that persons DBP and (2) the DASH diet can successfully be combined with