The truth about fats

Dietary fat is terribly misunderstood and mistakenly maligned nutrient. Myths and messages that have persisted since the 1960s warn that “fat is bad.” That dangerous oversimplification has helped launch dozens of largely ineffective diets and the development of thousands of fat-free but calorie-laden foods. It has also helped fuel the twin epidemics of obesity and type 2 diabetes. The message “fat is bad” is problematic because there are four main types of dietary fat with dramatically different effects on health.

Trans fats

Trans fats from partially hydrogenated oils are undeniably bad for the cardiovascular system and the rest of the body. These largely man-made fats elevate harmful low-density lipoprotein (LDL) cholesterol, reduce protective high-density lipoprotein (HDL) cholesterol, stimulate inflammation, and cause a variety of other changes that damage arteries and impair cardiovascular health. Higher intake of trans fat has been associated with an increased risk for developing cardiovascular disease, type 2 diabetes, gall stones, dementia, and weight gain

from red meat and dairy products increase harmful LDL but also increase HDL. A moderate intake of saturated fat (under 8% of daily calories) is compatible with a healthy diet, whereas consumption of greater amounts has been associated with cardiovascular disease.

Saturated fats

FOODS RICH IN OMEGA-6 FATS

-soybean, safflower, sunflower, corn, and other vegetable oils
-sunflower seeds, walnuts, and pine nuts
Dietary fat per se is not associated with the risk of chronic disease. In fact, diets that include up to 40% of calories from fat can be quite healthy if they are low in trans and saturated fat and emphasize polyunsaturated and monounsaturated fat. Although definitive data are not available on the optimal proportions of dietary fats, a low intake of trans and saturated fat and a higher intake of unsaturated fats reduce the risk of cardiovascular disease and diabetes.

MONOUNSATURATED AND POLYUNSATURATED FATS

fats from vegetable oils, seeds, nuts, whole grains, and fish—especially the polyunsaturated omega-3 fatty acids— are important components of a healthy diet and are also essential for cardiac health. Eating polyunsaturated fats in place of saturated and trans fats lowers harmful LDL, elevates protective HDL, improves sensitivity to insulin, and stabilizes heart rhythms.

GOOD SOURCES OF ESSENTIAL FATS

Many delicious foods deliver essential unsaturated fats that are good for the heart and the rest of the body. Try to eat at least one source of these every day.

FOODS RICH IN OMEGA-3 FATS

• cold-water fish such as salmon, sardines, mackerel, and trout
• canola and soybean oil (as long as they aren’t partially hydrogenated)
• flaxseeds and flaxseed oil
• walnuts
• dark green leafy vegetables such as kale, spinach, mustard greens, and collards
• omega-3 enhanced eggs

REFERENCE

1. Chowdhury R, Warnakula S, Kunutsor S, et al. Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary RiskA Systematic Review and Meta-analysis. Ann Intern Med2014;160:398-406.
2. Harcombe Z, Baker JS, Cooper SM, et al. Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review and meta-analysis. Open Heart2015;2:e000196.Abstract/FREE
3. Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr2010;91:535-46.Abstract/FREE

4. Hooper L, Martin N, Abdelhamid A, Davey Smith G. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database Syst Rev2015;6:CD011737.
5. Doell D, Folmer D, Lee H, Honigfort M, Carberry S. Updated estimate of trans fat intake by the US population. Food Addit Contam Part A Chem Anal Control Expo Risk Assess2012;29:861-74.

6. Eckel RH, Jakicic JM, Ard JD, et al. 2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol2014;63:2960 /1/9789241548441_eng.pdf.
7. Chien KL, Lin HJ, Hsu HC, et al. Comparison of predictive performance of various fatty acids for the risk of cardiovascular disease events and all-cause deaths in a community-based cohort. Atherosclerosis2013;230:140-7.
8. Wakai K, Naito M, Date C, Iso H, Tamakoshi A, Group JS. Dietary intakes of fat and total mortality among Japanese populations with a low fat intake: the Japan Collaborative Cohort (JACC) Study. Nutr Metab (Lond)2014;11:12.

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