November 2012 Issue
Micronutrients’ Role in Heart Disease — Some of Them Can Decrease or Increase the Risk
By Marie Spano, MS, RD, CSCS, CSSD
Vol. 14 No. 11 P. 20
Cardiovascular disease, which includes diseases of the heart and blood vessels, is the leading cause of death in both men and women in the United States.1,2 In 2008, coronary heart disease (CHD), the most common type of heart disease, accounted for almost one in four deaths in this country.1,2
Despite the widespread prevalence, there are several modifiable risk factors associated with heart disease, many of which are influenced by diet. And although changes in macronutrient intake, particularly fat, are often at the fore of dietary recommendations to prevent it, several micronutrients may increase or decrease its development and progression.
Micronutrients are substances such as vitamins and minerals that are needed in minuscule amounts to help the body produce enzymes, hormones, and other compounds essential for growth and repair.3 Though needed in small quantities, a suboptimal intake can impact various health parameters, and a deficiency can result in severe consequences, such as iron deficiency fatigue, decreased work or school performance, and impaired immune functioning, which can increase one’s risk of infection.
Each micronutrient discussed in this article is grouped into categories based on its influence on the development and progression of heart disease.
The role magnesium plays in heart health primarily has focused on its impact on heart rhythm and blood pressure. When given intravenously, it acts as a prophylactic in the prevention of postoperative atrial fibrillation following cardiac surgery.4 A meta-analysis of studies that examined magnesium supplementation and blood pressure found that this mineral has a small but clinically significant effect on reducing blood pressure.5
Additional support for magnesium comes from studies indicating that low serum magnesium levels contribute to the development of hypertension.6 And the Atherosclerosis Risk in Communities Study, which examined 13,922 adults from four communities in the United States, found adults with the lowest serum magnesium levels had a higher risk of CHD, suggesting that low magnesium also may contribute to atherosclerosis or acute thrombosis.7
Dietary potassium intake is tied to a dose-dependent decrease in blood pressure, though increasing dietary potassium intake will have a greater effect in those who also consume a high-sodium diet.8 And while a potassium-rich diet helps, particularly if sodium intake is high, studies show that increasing potassium intake may have a greater effect on blood pressure in blacks than whites.9
How does potassium intake correlate with CHD? A meta-analysis of 11 studies, including 247,510 adults, found higher dietary potassium intake—as assessed by 24-hour dietary recalls, food frequency questionnaires, and 24-hour urinary excretion—was associated with a 21% lower risk of stroke and a trend toward lower CHD risk.10
Not Beneficial or Inconclusive
Vitamin D is known primarily for its role in promoting bone health. Adequate levels of vitamin D are necessary for calcium absorption and maintaining proper blood levels of calcium and phosphorus. However, this micronutrient has captured a large part of the nutrition spotlight in recent years because of widespread vitamin D insufficiency and deficiency and the growing body of research highlighting its role in various aspects of health and disease.
While observational studies have found a significant association between low vitamin D levels and cardiovascular disease risk,11,12 a systematic review and meta-analysis of randomized trials examining vitamin D supplementation as an intervention didn’t show any beneficial effects of vitamin D supplementation on stroke, death, myocardial infarction, blood pressure, blood glucose, or blood cholesterol levels, with one exception—vitamin D supplementation led to a slight increase in HDL cholesterol.13
Another nutrient best known for its role in bone health is calcium. Earlier observational studies have found a small inverse relationship between dietary calcium intake and blood pressure,14 and supplementation with 400 to 2,000 mg of calcium per day has led to modest decreases in blood pressure.15 However, a more recent meta-analysis of 15 randomized controlled trials of calcium supplements (greater than 500 mg/day) given to adults (mean age of 40 and older) showed that calcium was associated with an increased risk of myocardial infarction.16
In addition, data from the Women’s Health Initiative Calcium/Vitamin D Supplementation Study, combined in a meta-analysis with eight other studies, found calcium supplements with or without vitamin D resulted in a modest increase in stroke and myocardial infarction risk. The study authors suggest two potential explanations: Abrupt increases in serum calcium levels after supplementation may increase vascular calcification and adversely affect risk of arterial thrombus formation.17 However, at this time, the majority of evidence doesn’t support an association between calcium intake and risk of cardiovascular disease.18
The micronutrient that has been linked to heart disease is sodium. Yet the effect of sodium on blood pressure varies between people and with those who are salt sensitive, which tends to increase with age. Salt-sensitive individuals benefit the most from sodium reduction. Those who aren’t salt sensitive won’t experience much change in blood pressure if they lower dietary sodium intake.19 However, reductions in sodium have a more profound impact on blood pressure in those who have a low dietary intake of potassium,9 particularly in men.20 A meta-analysis of 167 studies examining the effects of a high- or low-sodium diet found sodium reduction decreased blood pressure by 3.5%.21
The research on micronutrients and heart disease suggests a diet high in potassium- and magnesium-rich foods with adequate dietary calcium and vitamin D intake is optimal. Moreover, some individuals, particularly men, blacks, people who consume a low-potassium diet, and those who are sodium sensitive, will benefit from reducing their sodium to suggested intake levels—2,300 mg for those who are normotensive and 1,500 mg for those who are hypertensive or at risk of developing hypertension.
— Marie Spano, MS, RD, CSCS, CSSD, is a freelance writer and owns a sports nutrition and nutrition communications consulting company.
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21. Graudal NA, Hubeck-Graudal T, Jurgens G. Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines cholesterol, and triglyceride. Cochrane Database Syst Rev. 2011;(11):CD004022.