Dietary electrolytes and cardiovascular disease.
This quiz is an ideal activity for APD members to include in your CPD log, where it relates to personal learning goals. Record the time taken, to the nearest hour, to complete the quiz and any associated research.
A number of dietary electrolytes have been associated with a rise in blood pressure (BP). Raised BP is a major, preventable risk factor for cardiovascular disease (CVD), including stroke, coronary heart disease, heart failure, peripheral vascular disease and kidney failure. (1) The risk of CVD increases as the level of BP increases. In addition to the physiological effects resulting from variations in the intakes of electrolytes, there may be significant interactions between these electrolytes that affect CVD risk. This continuing education quiz refers to the findings of the Summary of Evidence review on dietary electrolytes, blood pressure and CVD conducted by the National Heart Foundation of Australia in 2006. (2) The electrolytes considered were sodium, potassium, magnesium and calcium.
1. Which statement best describes the evidence relating to calcium and BP or CVD, and magnesium and BP or CVD?
a. There is evidence for a relationship between magnesium and BP but not for calcium and BP
b. There is no evidence to support an association between magnesium and BP or CVD, but evidence to support an association between calcium and BP
c. There is no evidence to support a relationship between calcium and BP, or for an association between magnesium and BP or CVD
d. There is evidence to support a relationship between magnesium and BP, and calcium and BP, but no evidence to support an association between magnesium and CVD
2. The National Heart Foundation of Australia recommends all Australians reduce their salt intake to less than 6 g of salt a day. This amount of salt is equal to
a. 2000 mg of sodium
b. 2300 mg of sodium
c. 3200 mg of sodium
d. 1600 mg of sodium
3. There is good evidence to show that a reduction in dietary sodium of approximately 1700 mg/day results in a fall of ___ mmHg in hypertensive individuals (systolic BP [greater than or equal to]140 mmHg) and a fall of ___ mmHg in normotensive individuals (systolic BP <120 mmHg).
a. 4-5, 2
b. 2, 2-3
c. 2-3, 1
d. 5-6, 4
4. There is good evidence in the scientific literature to indicate that a general reduction in sodium intake could be best achieved by a reduction in the sodium content of manufactured foods rather than by dietary advice alone because the sodium added to processed food contributes about ___ of dietary sodium.
5. There is good evidence in the scientific literature to indicate that an increased intake of dietary potassium of approximately 2100 mg/day is associated with a fall in systolic BP of ___ mmHg in hypertensive individuals and a fall in systolic BP of ___ mmHg in normotensive individuals.
a. 5-6, 3
b. 4-8, 2
c. 2-3, 1
d. 2-5, 2
6. There is moderate evidence in the scientific literature to indicate that:
a. A high dietary sodium intake is associated with increased stroke incidence, and mortality from coronary heart disease and CVD
b. A high potassium intake is associated with decreased stroke mortality
c. Reducing dietary sodium and increasing dietary potassium intake is associated with a reduced risk of CVD d. Both a and b
7. When advising patients or clients with high BP or those at risk of CVD, the Heart Foundation recommends:
a. Advising patients to reduce their salt intake to less than 6 g of salt (2300 mg of sodium) a day
b. Advising patients to reduce their salt intake to less than 4 g of salt (1550 mg of sodium) a day
c. Advising patients to reduce dietary sodium intake along with weight loss for greater benefits in reduction of BP
d. Advising patients to reduce their salt intake to 1.2-1.6 g of salt (460-920 mg of sodium) a day
For more information about the Heart Foundation Position Statement regarding the relationship between dietary electrolytes and CVD, visit http://www.heartfoundation.org.au and click on Professional Information then Nutrition.
The evidence obtained from a systematic review of all relevant randomised controlled trials is considered to be the most robust and good-quality evidence. (3) The Heart Foundation has based its conclusions on the highest-quality evidence available after assessing each paper individually. The criteria used to appraise the evidence were based on consistency across a range of study designs, the quality of each study and consideration of measurement bias, the size of the effects and the demonstration of a biologically plausible mechanism. The terms 'good', 'moderate' and 'weak' evidence were used to assess the strength of the scientific evidence.
The scientific literature review undertaken by the National Heart Foundation of Australia found there is limited evidence currently available regarding the impact of dietary magnesium and calcium on BP and CVD. The review found no evidence to support an association between calcium and BP, and weak evidence that high calcium intake reduces the risk of ischaemic stroke. (4-8) The review also found no evidence to support an association between magnesium and BP or magnesium and CVD.
Australian adults eat about 9 g of salt a day. (9,10) The National Heart Foundation recommends that Australians reduce their intake to less than 6 g of salt a day These recommendations are consistent with the 2006 National Health and Medical Research Council Nutrient Reference Values for Australia and New Zealand. (11) Six grams of salt contains approximately 100 mmol of sodium or 2300 milligrams of sodium. In order to know how much salt is in food, advise patients to look at the Nutrition Information Panel on food packages. Salt is not shown on the label, so the patient must look for the figure for sodium in milligrams per 100 g. Australians can reduce their sodium/salt intake by eating plenty of fresh fruit and vegetables, choosing 'no added salt', 'low salt' or 'reduced salt' if lower-salt options are not available, avoiding high-salt foods particularly processed meats, commercial sauces, commercial soups and stocks, high-salt take-away and snack foods, and avoiding adding salt while cooking and at the table.
Reducing dietary sodium is associated with a fall in blood pressure in hypertensive and normotensive individuals. There is good evidence in the scientific literature to indicate that a reduction in dietary sodium of approximately 1700 mg/day (75 mmol/day) results in a fall in systolic blood pressure of 4-5 mmHg in hypertensive individuals (systolic BP [greater than or equal to]140 mmHg) and a fall in systolic blood pressure of 2 mmHg in normotensive individuals (systolic BP <120 mmHg).12,13
A reduction in sodium intake could be better achieved by a general reduction in the sodium content of manufactured food products than by dietary advice alone, and whole foods have a greater effect on BP than supplements. (8,14) The greater impact of reducing sodium in manufactured food products results from the finding that processed foods contribute to 80% of dietary sodium. (15)
Australian men eat about 2800-3200 mg of potassium per day and women about 2600-2900 mg of potassium per day. (9,10) The National Health and Medical Research Council recommend that men eat 3800 mg of potassium per day and women eat 2800 mg of potassium per day in order to prevent deficiency. (11) To prevent chronic disease (including CVD), the recommended intake is 4700 mg per day. The National Heart Foundation found good evidence in the scientific literature to make recommendations to increase potassium for normotensive (systolic BP <120 mmHg) and hypertensive (systolic BP >140 mmHg) individuals. (16-18) The National Heart Foundation found less evidence that focused on mildly hypertensive individuals (systolic BP = 120-139 mmHg), and has not made recommendations for this group. For individuals with high blood pressure, at high risk or with existing CVD, the National Heart Foundation recommends increasing potassium intake to at least 4700 mg a day by eating vegetables, fruits, nuts, legumes and wholegrain cereals regularly (Note: people with renal impairment should check with their doctor before changing potassium intake.)
The scientific literature review undertaken by the National Heart Foundation found that high dietary sodium intake is associated with increased stroke incidence, and mortality from coronary heart disease and CVD. (19,20) A high potassium intake is associated with decreased stroke mortality. (21-25) Further studies are needed to clarify the evidence that reducing dietary sodium and increasing potassium intake is associated with a reduced risk of CVD.
The National Heart Foundation recommends that patients or clients with high BP, or those with or at risk of CVD, reduce their salt intake to less than 4 g of salt a day (approximately 1550 mg of sodium). These recommendations are consistent with the National Health and Medical Research Council's Nutrient Reference Values for Australia and New Zealand, which recommend a Suggested Dietary Target sodium intake of 1600 mg per day. (11) Further studies are needed to clarify the evidence that reductions in dietary sodium intake, along with weight loss, facilitate greater benefits in reduction of BP.
1 Australian Institute of Health and Welfare. Australia's Health. Canberra: Australian Institute of Health and Welfare, 2006.
2 National Heart Foundation of Australia. Summary of Evidence on the Relationships between Dietary Electrolytes and Cardiovascular Disease. Sydney: National Heart Foundation of Australia, December 2006. (Cited 24 Jul 2007.) Available from URL: http://www.heartfoundation.org.au/Professional_Information/Lifestyle_Risk/Nutrition.htm.
3 National Health and Medical Research Council. A Guide to the Development, Implementation and Evaluation of Clinical Practice Guidelines. Canberra: NHMRC, 1999.
4 Abbott R, Curb J, Rodriguez B, Sharp D, Burchfiel C, Yano K. Effect of dietary calcium and milk consumption on risk of thromboembolic stroke in older middle-aged men. Honolulu Heart Program Stroke 1996; 27: 813-18.
5 Elwood P, Strain J, Robson P et al. Milk consumption, stroke, and heart attack risk: evidence from the Caerphilly cohort of older men. J Epidemiol Community Health 2005; 59: 502-5.
6 Iso H, Stampfer M, Manson J et al. Prospective study of calcium, potassium and magnesium intake and risk of stroke in women. Stroke 1999; 30: 1772-9.
7 Umesawa M, Iso H, Date C et al. Dietary intake of calcium in relation to mortality from cardiovascular disease: the JACC Study. Stroke 2006; 37: 20-26.
8 Griffith L, Guyatt G, Cook R, Bucher H, Cook D. The influence of dietary and non-dietary calcium supplementation on blood pressure: an updated meta-analysis of randomized controlled trials. Am J Hypertens 1999; 12: 84-92.
9 Beard T, Woodward D, Ball PJ, Hornsby H, von Witt RJ, Dwyer T. The Hobart Salt Study 1995: few meet national sodium intake target. Med J Aust 1997; 166: 404-7.
10 Notowidjojo L, Truswell AS. Urinary sodium and potassium in a sample of healthy adults in Sydney, Australia. Asia Pacific J Clin Nutr 1993; 2: 25-33.
11 National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand Including Recommended Dietary Intakes. Canberra: NHMRC, 2006.
12 He F, MacGregor G. Effect of modest salt reduction on blood pressure: a meta-analysis of randomised trials. Implications for public health. J Hum Hypertens 2002; 16: 761-70.
13 Cutler J, Follmann D, Allender P. Randomized trials of sodium reduction: an overview. Am J Clin Nutr 1997; 65: 643S-51S.
14 Hooper L, Bartlett C, Davey Smith G, Ebrahim S. Systematic review of long term effects of advice to reduce dietary salt in adults. BMJ 2002; 325: 628.
15 Sacks F, Svetkey L, Vollmer W et al. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group. N Engl J Med 2001; 344: 3-10.
16 Whelton P, He J, Cutler J et al. Effects of oral potassium on blood pressure: meta-analysis of randomised controlled clinical trials. JAMA 1997; 277: 1624-32.
17 Geleijnse J, Kok F, Grobbee D. Blood pressure response to changes in sodium and potassium intake: a metaregression analysis of randomised trials. J Hum Hypertens 2003; 17: 471-80.
18 Cappuccio F, Markandu N, Carney C, Sagnella G, MacGregor G. Double-blind randomised trial of modest salt restriction in older people. Lancet 1997; 350: 850-54.
19 He J, Ogden L, Vupputuri S, Bazzano L, Loria C, Whelton P. Dietary sodium intake and subsequent risk of cardiovascular disease in overweight adults. JAMA 1999; 282: 2027-34.
20 Tuomilehto J, Jousilahti P, Rastenyte D et al. Urinary sodium excretion and cardiovascular mortality in Finland: a prospective study. Lancet 2001; 357: 848-51.
21 Ascherio A, Rimm E, Hernan M et al. Intake of potassium, magnesium, calcium, and fiber and risk of stroke among US men. Circulation 1998; 98: 1198-204.
22 Chang H, Hu Y, Yue C et al. Effect of potassium-enriched salt on cardiovascular mortality and medical expenses of elderly men. Am J Clin Nutr 2006; 83: 1289-96.
23 Fang J, Madhavan S, Alderman M. Dietary potassium intake and stroke mortality. Stroke 2000; 31: 1532-7.
24 Khaw KT, Barrett-Connor E. Dietary potassium and stroke-associated mortality. A 12-year prospective population study. N Engl J Med 1987; 316: 235-40.
25 Xie J, Sasaki S, Joossens J, Kesteloot H. The relationship between urinary actions obtained from the INTERSALT study and cerebrovascular mortality. J Hum Hypertens 1992; 6: 17-21.
This quiz has been prepared by Christina Black, Shanthi Thuraisingam and Barbara Eden, of the National Heart Foundation of Australia. Correspondence should be directed to Heartline 1300 36 27 87 or Barbara Eden, Executive Officer, National Nutrition Program, Heart Foundation, firstname.lastname@example.org
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|Title Annotation:||CONTINUING EDUCATION QUIZ|
|Author:||Black, Christina; Thuraisingam, Shanthi; Eden, Barbara|
|Publication:||Nutrition & Dietetics: The Journal of the Dietitians Association of Australia|
|Date:||Sep 1, 2007|
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