How to Address Common Diet & Cardiovascular Disease Myths

By Donna Kwan, RD posted in Professionals & Educators
Updated

basketeggsPeople living with diabetes are at a high risk of developing cardiovascular disease (CVD). Lifestyle changes that include healthy nutrition are an important factor in reducing the risk of cardiovascular disease in individuals with diabetes. However, many misconceptions regarding cardiovascular disease and dietary choices are present. Five common myths are dispelled in the following article.

MYTH 1:

Eggs can only be consumed once a week

FACT:
Various heart health organizations currently suggest that eggs can be part of a healthy diet. The Heart and Stroke Foundation of Canada suggests enjoying an egg every now and again is okay, but not daily and the American Heart Association guidelines no longer include limiting egg consumption as a recommendation.

The epidemiological literature does not support the idea that egg consumption is a risk factor for coronary disease according to a review by Kritchevsky.1 Diabetic individuals however, may be more at risk with higher egg consumption than suggested for the general population according to a large prospective epidemiological study involving over 37,000 men and over 80,000 women.2 In this study, consumption of up to one egg per day was found to have little risk of coronary heart disease (CHD) or stroke for the general population. In diabetic individuals, the relative risk of CHD for men was 1.16 with 2 to 4 eggs per week but 2.02 with intake of 1 or more eggs per day. For females, the relative risk for egg intake of 2 to 4 eggs per week was 1.05 and increases to 1.49 for intake of 1 or more eggs per day. Therefore, although eggs do not have to be restricted to one time per week, one egg per day is cautioned.

Some of the concern with consuming eggs is the high amount of cholesterol one egg contains. Research has shown that the total saturated fat and trans fat consumed per day results in a greater increase in blood cholesterol and risk of heart disease than the cholesterol in food. Canadian guidelines suggest <10% of energy should be consumed as saturated and trans fats.3 One egg contains 1.5 grams of saturated fat and no trans fat. For an individual consuming a 2000 kcal diet, their maximum saturated fat intake should be 22 grams. Therefore, if an individual chooses low saturated and trans fat foods such as fruits and vegetables, whole grains, low fat dairy products, and lean meats or meat alternatives, eggs can be enjoyed more frequently than once a week. Consuming eggs 2 to 4 times per week may be suggested to diabetic patients.

MYTH 2:

All fibre can help lower cholesterol

FACT:
There are two type of fibre: soluble and insoluble fibre. Foods containing soluble fibre include oats, psyllium, barley, beans and lentils, and fruits such as pears and apples. Foods consisting mainly of insoluble fibre include wheat bran, corn bran, fruits such as berries and vegetables such as spinach.

Numerous studies have reported the beneficial effects of soluble fibre on CVD risk which has resulted in a health claim to be made by the US Food and Drug Administration.4 This health claim indicates that diets that are low in saturated fat and cholesterol and that include soluble fiber from certain foods “may” or “might” reduce the risk of heart disease.4 Canada does not currently have a health claim for soluble fibre.

Choosing whole grains as part of a healthy diet is a general dietary recommendation in the Canadian Diabetes Association 2003 Clinical Practice Guidelines.3 Studies have suggested total fibre intake should be 25-35g/d, however, soluble fibre should be included in this total. A study involving individuals consuming increased total fibre have shown a reduction in LDL (low density lipoprotein) cholesterol as a result of the soluble fibre having a greater effect in lowering LDL-cholesterol than the insoluble fibre.5 This study showed that a high fibre diet consisting of 25g of soluble fibre and 25g of insoluble fibre lowered vLDL (very low density lipoprotein) cholesterol by 12.5% (P=0.01) and triglycerides by 10.2% (P=0.02) compared to a diet consisting of 8g of soluble fibre and 16g of insoluble fibre.5

Therefore, an individual consuming only insoluble fibre will not reap the cholesterol lowering benefits found in the research.

MYTH 3:

Nuts are high in fat and therefore are unhealthy

FACT:
Yes, nuts are high in fat, however, nuts are high in healthy fats such as monounsaturated and polyunsaturated fats.

Studies focusing on individual types of nuts such as almonds and walnuts have shown to significantly reduce heard disease risk factors such as LDL cholesterol, LDL:HDL cholesterol, and lipoprotein(a).6,7 However, one nut has not been found to be better than another in reducing heart disease risk. According to a systematic review of studies on nuts and the effect on blood lipid profiles in humans, consumption of approximately 50-100g of nuts > or = 5 times per week as part of a heart-healthy diet may significantly decrease total cholesterol and LDL cholesterol.8 Total fat content should be approximately 35% of energy and comprise mainly monounsaturated and polyunsaturated fats. Authors noted that macadamia nuts showed less convincing results than other nuts.

MYTH 4:

All trans fatty acids (trans fats) are unhealthy

FACT:
Many studies have linked higher intakes of trans fatty acids to elevated blood lipids and risk for cardiovascular disease.9 However, there are naturally occurring trans fatty acids and industrially produced trans fatty acids (e.g. partially hydrogenated margarines) by a process called hydrogenation. Most if not all the studies showing risk for heart disease and intake of trans fatty acid are involving industrially produced trans fatty acids.9 The naturally occurring trans fatty acids are found in small quantities in dairy and beef products. Studies to date have not shown the same increased risk for heart disease with naturally occurring trans fatty acids.10,11 Moreover, the naturally occurring trans fatty acid in dairy and beef products is partially converted to conjugated linoleic acid (CLA), a fat that is currently studied for a variety of health benefits.

Therefore, intake of naturally occurring trans fatty acid poses no known health risk and may have health benefits while industrially produced trans fat are to be avoided.

MYTH 5:

If it’s trans-fat free or has zero trans fat, it’s okay to eat

FACT:
Many products are now labeled as trans-fat free. Food labels help to determine the amount of saturated and trans fat in the product. The less trans fat there is in a product usually results in a healthier product. But keep in mind; foods labeled trans-fat-free may still contain small amounts of hydrogenated oils. Health Canada guidelines indicate a trans-fat-free claim can be used for products that contain less than 0.2 grams of trans fat per reference amount and serving, and must be low in saturated fat.12 This claim is based on the serving size amount. Therefore, if the serving size consumed is greater than the serving size listed, higher amounts of trans fats may be consumed. As well, higher amounts of saturated fats and calories may also be consumed.

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Some products may also contain sources of saturated fat to replace the trans fat and excess intake of saturated fats have long been known to increase risk for heart disease. Therefore if products are eliminating trans fat but continuing to use saturated fat, the product continues to be a less healthy choice compared to foods such as fresh fruits and vegetables.

References

1. Kritchevsky SB. A review of scientific research and recommendations regarding eggs. J Am Coll Nutr. 2004 Dec;23(6 Suppl):596S-600S.

2. Hu FB et al. A Prospective Study of Egg Consumption and Risk of Cardiovascular Disease in Men and Women. JAMA. 1999;281:1387-1394.

3. Canadian Diabetes Association Clinical Practice Guidelines Expert Committee. Canadian Diabetes Association 2003 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada. Can J Diabetes. 2003;27(suppl 2).

4. US Food and Drug Administration. Health Claims: Soluble Fiber From Certain Foods and Risk of Heart Diseases. Publisher: Code of Federal Regulations, location not known. 2001;21:101.81.

5. Chandalia M et al. Beneficial Effects of High Dietary Fiber Intake in Patients with Type 2 Diabetes Mellitus. N Engl J Med. 2000;342:1392-1398.

6. Jenkins DJA et al. Dose Response of Almonds on Coronary Heart Disease Risk Factors: Blood Lipids, Oxidized Low-Density Lipoproteins, Lipoprotein(a), Homocysteine, and Pulmonary Nitric Oxide. Circulation. 2002;106:1327-1332.

7. Ros E et al. A Walnut Diet Improves Endothelial Function in Hypercholesterolemic Subjects. Circulation. 2004;109:1609-1614.

8. Mukuddem-Petersen J, Oosthuizen W, Jerling JC. A systematic review of the effects of nuts on blood lipid profiles in humans. J Nutr. 2005 Sep;135(9):2082-9.

9. Mozaffarian D et al. Trans fatty acids and cardiovascular disease. N Engl J Med. 2006 Apr 13;354(15):1601-13.

10. Stender S & Dyerberg J. (2003) The Influence of trans fatty acids on health. Fourth Edition. A Report from the Danish Nutrition Council. Retrieved May 10, 2006: http://www.meraadet.dk/gfx/uploads/Rapporter_pdf/Trans%20fatty%20acids_4.th%20ed._UK_www.pdf

11. Tricon S et al. Effects of dairy products naturally enriched with cis-9, trans-11 conjugated linoleic acid on the blood lipid profile in healthy middle-aged men. Am J Clin Nutr. 2006 Apr;83(4):744-53.

12. Canadian Food Inspection Agency. 2003 Guide to Food Labeling and Advertising. Chapter 7 Nutrient Content Claims. Retrieved May 15, 2006: http://www.inspection.gc.ca/english/fssa/labeti/guide/ch7ae.shtml#7.18

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About the Author

Donna Kwan currently works as a clinical dietitian within the Diabetes Comprehensive Care Program at St. Michael’s Hospital in Toronto. Donna’s past work experience have included diabetes, lipid and weight management counseling at a private endocrinology clinic where she also was involved in clinical research as a coordinator for almost two years.