Hypertension
Approximately 25% of Egyptian adults are hypertensive and, therefore, at relatively greater risk of cardiovascular disease (particularly ischemic heart disease) and stroke.1 Lifestyle modification - including regular exercise, maintaining a healthy body weight, moderating alcohol intake, abstaining from smoking, reducing sodium consumption, meeting recommended intakes of calcium, magnesium and potassium, and/or reducing stress - can help prevent, and sometimes control hypertension.1,2
Key Messages from DASH
The Importance of Calcium
The Link Between Calcium and Sodium
A Note on Weight Control
References
Key Messages from DASH
The Importance of Calcium
The Link Between Calcium and Sodium
A Note on Weight Control
References
Key Messages from DASH (Dietary Approaches to Stop Hypertension)
1- It's the milk products
Reductions in blood pressure of the magnitude achieved by the DASH diet – rich in milk products, fruits and vegetables – could translate into a 15% reduction in ischemic heart disease and a 27% reduction in stroke.3
The DASH trial studied the effects of dietary patterns on blood pressure. Following the consumption of a control diet for three weeks, 459 adults were randomized to maintain that diet, or to continue either on a diet high in fruits and vegetables (8-10 servings) or a combination diet high in fruits and vegetables plus milk products (2.7 servings).3 (Kudos if you recognize the similarity to Food Guide to Healthy Eating!) Within two weeks, both test diets effectively lowered blood pressure, with similar patterns of reductions observed in men and women, minorities and nonminorities.
For the total cohort, the dairy-enriched combination diet had twice the impact of the fruits and vegetables diet, reducing systolic blood pressure (SBP) by 5.5 mm Hg and diastolic blood pressure (DBP) by 3.0 mm Hg (P<0.001 for each) more than the control diet. Among hypertensive subjects, the combination diet reduced SBP and DBP by 11.4 and 5.5 mm Hg more than the control diet (P<0.001 for each) - making it a viable alternative to monotherapy for mild hypertension.3,4 *
Unfortunately, Canadians fail to consume even the minimum two servings of milk products5 or the minimum five servings of vegetables and fruits recommended in Food Guide.6
* Important note: Since weight and sodium intake (3,000 mg) were held constant and alcohol intake was similar in all three groups, these well-known confounders did not account for the observed reductions in blood pressure.3
2- It's not the absence of fat
Although the DASH combination diet was low in fat, saturated fat and cholesterol, it was the presence of calcium-rich milk products, and not the absence of fat, that made the difference. In fact, the amount of total fat or the proportions of saturated to unsaturated fats has little, if any, impact on blood pressure.2 Recommendations to reduce dietary saturated fat and cholesterol speak more to cardio-vascular health than to prevention or treatment of hypertension.2
3- It's not a single nutrient
It is not possible to identify any single nutrient as the miracle factor in preventing hypertension, or for that matter any other chronic condition. Rather, a well-balanced diet rich in fruits, vegetables and milk products - providing potassium, magnesium and calcium, as well as many other nutrients - is the best recommendation you can offer your patients.
That said, calcium almost certainly appears to be a key factor - its content in the combination diet was more than double that in the fruits and vegetables diet, whereas potassium and magnesium contents were similar.3 The effects of the fruits and vegetables diet on blood pressure are comparable to those reported in randomized, controlled trials of potassium and hypertension.4,7
4- The DASH combination diet is effective for everybody
The DASH combination diet was shown to lower blood pressure in virtually all subgroups.3
It is, therefore, an intervention with the potential to be effective in a broad cross section of the population, including those at high risk of hypertension and its sequelae.3,8 In terms of systolic blood pressure, African-Americans benefited significantly more than Caucasians, and hypertensives significantly more than normotensives.8 African-Americans (who are particularly susceptible to salt sensitivity9,10 ) are twice as likely as Caucasians to develop hypertension.11
Is lactose intolerance a problem for them? Although more than 60% of DASH participants were African-American, the combination diet with 2.7 servings of milk products daily resulted in fewer reported symptoms of lactose intolerance than the (typically American) control-diet containing a mere half serving of milk products a day.3,11
The Importance of Calcium
Research indicates that dietary calcium not only plays an integral role in normal blood pressure maintenance, but that insufficient calcium is also associated with an increased risk of hypertension.12-15
In fact, an inverse relationship between calcium and blood pressure has been observed in virtually all population groups studied and across racial groups, even after adjustment for possible confounding factors.12,13
Updated meta-analyses of randomized clinical trials comparing calcium supplements and calcium derived from foods have confirmed that food calcium has twice the impact on hypertension.15,16 Moreover, there was a greater consistency in the results from dietary calcium trials. It may not be just the calcium that is responsible for its more favourable impact on blood pressure, but the critical interaction among milk nutrients.11
Guidelines for the prevention and treatment of hypertension recommend that individuals maintain adequate intake of dietary calcium (defined as 1,000 mg), as well as potassium and magnesium for general health, but do not advocate the use of supplements of these minerals.2,17 Unfortunately, average calcium intakes (except by males 18 to 34 years of age) fall far short of the new higher calcium recommendations - 1,000 mg/day for adults 19 to 50 years of age and 1,200 mg for those over 50 - and decrease with age, especially in women.5,18
The Link between Calcium and Sodium
The importance of sodium restriction in the prevention and treatment of hypertension is controversial.19 Although it is ineffective for preventing high blood pressure in normotensives,20,21 there is some evidence that as a complement to drug therapy it may benefit elderly hypertensives.19,21 The DASH-Sodium trial suggests that the DASH diet, in combination with salt restriction, may be effective in normotensives as well.22
Whatever salt's impact, it does appear to be mitigated by calcium.10,23 Since sodium and calcium share the same transport system in the proximal tubule, every 100 mmol of sodium excreted by the kidney takes 1-1.5 mmol of calcium along with it.24 It has been shown that subjects who consume a higher sodium diet actually have the lowest blood pressure provided their dietary calcium exceeds 800 mg.10,23,25
The effect of sodium on blood pressure is determined by the adequacy of other minerals, particularly calcium10,23 and potassium.9 Adequate calcium appears to be protective against the hypertensive effects of high sodium, low potassium, and high alcohol intakes.10,23,25,26 And that's good news, since there's no question it's easier to add milk products, fruits and vegetables to the diet than to restrict salt.
A Note on Weight Control
There is no question that weight loss reduces blood pressure in overweight or obese individuals,27,28 but admonishing these patients to achieve their ideal weight may be unrealistic and counterproductive.29 Although the initial goal should be to reduce body weight by approximately 10%,28 even losses as small as 4.5 kg (10 lbs) have been shown to effectively reduce blood pressure in many overweight hypertensive patients.2
1- It's the milk products
Reductions in blood pressure of the magnitude achieved by the DASH diet – rich in milk products, fruits and vegetables – could translate into a 15% reduction in ischemic heart disease and a 27% reduction in stroke.3
The DASH trial studied the effects of dietary patterns on blood pressure. Following the consumption of a control diet for three weeks, 459 adults were randomized to maintain that diet, or to continue either on a diet high in fruits and vegetables (8-10 servings) or a combination diet high in fruits and vegetables plus milk products (2.7 servings).3 (Kudos if you recognize the similarity to Food Guide to Healthy Eating!) Within two weeks, both test diets effectively lowered blood pressure, with similar patterns of reductions observed in men and women, minorities and nonminorities.
For the total cohort, the dairy-enriched combination diet had twice the impact of the fruits and vegetables diet, reducing systolic blood pressure (SBP) by 5.5 mm Hg and diastolic blood pressure (DBP) by 3.0 mm Hg (P<0.001 for each) more than the control diet. Among hypertensive subjects, the combination diet reduced SBP and DBP by 11.4 and 5.5 mm Hg more than the control diet (P<0.001 for each) - making it a viable alternative to monotherapy for mild hypertension.3,4 *
Unfortunately, Canadians fail to consume even the minimum two servings of milk products5 or the minimum five servings of vegetables and fruits recommended in Food Guide.6
* Important note: Since weight and sodium intake (3,000 mg) were held constant and alcohol intake was similar in all three groups, these well-known confounders did not account for the observed reductions in blood pressure.3
2- It's not the absence of fat
Although the DASH combination diet was low in fat, saturated fat and cholesterol, it was the presence of calcium-rich milk products, and not the absence of fat, that made the difference. In fact, the amount of total fat or the proportions of saturated to unsaturated fats has little, if any, impact on blood pressure.2 Recommendations to reduce dietary saturated fat and cholesterol speak more to cardio-vascular health than to prevention or treatment of hypertension.2
3- It's not a single nutrient
It is not possible to identify any single nutrient as the miracle factor in preventing hypertension, or for that matter any other chronic condition. Rather, a well-balanced diet rich in fruits, vegetables and milk products - providing potassium, magnesium and calcium, as well as many other nutrients - is the best recommendation you can offer your patients.
That said, calcium almost certainly appears to be a key factor - its content in the combination diet was more than double that in the fruits and vegetables diet, whereas potassium and magnesium contents were similar.3 The effects of the fruits and vegetables diet on blood pressure are comparable to those reported in randomized, controlled trials of potassium and hypertension.4,7
4- The DASH combination diet is effective for everybody
The DASH combination diet was shown to lower blood pressure in virtually all subgroups.3
It is, therefore, an intervention with the potential to be effective in a broad cross section of the population, including those at high risk of hypertension and its sequelae.3,8 In terms of systolic blood pressure, African-Americans benefited significantly more than Caucasians, and hypertensives significantly more than normotensives.8 African-Americans (who are particularly susceptible to salt sensitivity9,10 ) are twice as likely as Caucasians to develop hypertension.11
Is lactose intolerance a problem for them? Although more than 60% of DASH participants were African-American, the combination diet with 2.7 servings of milk products daily resulted in fewer reported symptoms of lactose intolerance than the (typically American) control-diet containing a mere half serving of milk products a day.3,11
The Importance of Calcium
Research indicates that dietary calcium not only plays an integral role in normal blood pressure maintenance, but that insufficient calcium is also associated with an increased risk of hypertension.12-15
In fact, an inverse relationship between calcium and blood pressure has been observed in virtually all population groups studied and across racial groups, even after adjustment for possible confounding factors.12,13
Updated meta-analyses of randomized clinical trials comparing calcium supplements and calcium derived from foods have confirmed that food calcium has twice the impact on hypertension.15,16 Moreover, there was a greater consistency in the results from dietary calcium trials. It may not be just the calcium that is responsible for its more favourable impact on blood pressure, but the critical interaction among milk nutrients.11
Guidelines for the prevention and treatment of hypertension recommend that individuals maintain adequate intake of dietary calcium (defined as 1,000 mg), as well as potassium and magnesium for general health, but do not advocate the use of supplements of these minerals.2,17 Unfortunately, average calcium intakes (except by males 18 to 34 years of age) fall far short of the new higher calcium recommendations - 1,000 mg/day for adults 19 to 50 years of age and 1,200 mg for those over 50 - and decrease with age, especially in women.5,18
The Link between Calcium and Sodium
The importance of sodium restriction in the prevention and treatment of hypertension is controversial.19 Although it is ineffective for preventing high blood pressure in normotensives,20,21 there is some evidence that as a complement to drug therapy it may benefit elderly hypertensives.19,21 The DASH-Sodium trial suggests that the DASH diet, in combination with salt restriction, may be effective in normotensives as well.22
Whatever salt's impact, it does appear to be mitigated by calcium.10,23 Since sodium and calcium share the same transport system in the proximal tubule, every 100 mmol of sodium excreted by the kidney takes 1-1.5 mmol of calcium along with it.24 It has been shown that subjects who consume a higher sodium diet actually have the lowest blood pressure provided their dietary calcium exceeds 800 mg.10,23,25
The effect of sodium on blood pressure is determined by the adequacy of other minerals, particularly calcium10,23 and potassium.9 Adequate calcium appears to be protective against the hypertensive effects of high sodium, low potassium, and high alcohol intakes.10,23,25,26 And that's good news, since there's no question it's easier to add milk products, fruits and vegetables to the diet than to restrict salt.
A Note on Weight Control
There is no question that weight loss reduces blood pressure in overweight or obese individuals,27,28 but admonishing these patients to achieve their ideal weight may be unrealistic and counterproductive.29 Although the initial goal should be to reduce body weight by approximately 10%,28 even losses as small as 4.5 kg (10 lbs) have been shown to effectively reduce blood pressure in many overweight hypertensive patients.2
The general focus on sodium restriction as the primary nonpharmacologic therapeutic approach to hypertension has impeded recognition of other potentially more important factors, such as maintaining adequate intakes of calcium, potassium and magnesium.10
References:
References:
1. Campbell NR et al. 1999. CMAJ 160(9 Suppl):S1-6.
2. Sheps SG (chair). 1997. National Institutes of Health, Bethesda, Maryland. NIH Publication, No. 98-4080.
3. Appel LJ et al. 1997. N Eng J Med 336:1117-24.
4. Zemel MB. 1997. Nutr Reviews 55:303-5.
5. Bertrand L. 1995. Gouvernement du Québec, Santé Québec.
6. Angus Reid Group. 1992. Angus Reid Group, Toronto, ON.
7. Whelton PK et al. 1997. JAMA 277:1624-32.
8. Svetkey LP et al. 1999. Arch Intern Med 159:285-93.
9. Morris C et al. 1999. Hypertension 33:18-23.
10. McCarron DA. 1997. Am J Clin Nutr 65(Suppl)712S-16S.
11. McCarron DA et al. 1998. Am J Clin Nutr 68:517-18.
12. McCarron DA et al. 1991. Am J Clin Nutr 54:215S-19S.
13. Osborne CG et al. 1996. Nutr Reviews 54:365-81.
14. Allender PS et al. 1996. Ann Intern Med 124:825-31.
15. Bucher HC et al. 1996. JAMA 275:1016-22.
16. Griffith LE et al. 1999. Am J Hypertens 12:84-92.
17. Burgess E et al. 1999. CMAJ 160(9 Suppl):S35-45.
18. Nova Scotia Heart Health Program. 1993. Nova Scotia Department of Health, Halifax, N.S.
19. Chrysant GS et al. 1999. Prog Cardiovascular Dis 42:123-38.
20. Fodor JG et al. 1999. CMAJ 160(9 Suppl):S29-34.
21. Midgley JP et al. 1996. JAMA 275:1590-97.
22. Sacks FM et al. 2001. N Eng J Med 344:3-10.
23. Hamet P et al. 1992. Am J Hypertens 5(6 Pt 1):378-85.
24. Heaney RP. 1994. MD (June 6-8, 1994).
25. Gruchow HW et al. 1988. Am J Clin Nutr 48:1463-70.
26. Hamet P et al. 1991. Hypertension 17(suppl I):I-150-54.
27. Leiter LA et al. 1999. CMAJ 160(9 Suppl):S7-12.
28. Expert Panel on the Identification, Evaluation and Treatment of Overweight Adults. 1998. Am J Clin Nutr 68:899-917.
|
|
|
Ph.D., Justus liebig University, Giessen, West Germany. Professor,Department of Food Science. University of Ain Shams. Cairo, Egypt. Expert and consultant(dairy, food, water and nutrition |
