The Role of Carbohydrate Restriction in Reducing Cardiac Risk Factors
One in five adults has some form of cardiovascular disease (1). A
recent flood of clinical research suggests that the time for
re-evaluating nutritional recommendations for bringing heart disease
under control may be well overdue. It is a known fact that
carbohydrates increase triglyceride levels. Triglycerides, total
cholesterol, LDL ("bad") and HDL ("good") cholesterol are fats that
your physician tests for when you get your blood tested.
Elevated Triglyceride Levels Are an Independent Risk Factor for Heart
Recently, 17 studies involving over 46,000 men followed over
eight years and nearly 11,000 women followed over 11 years indicated
that a small elevation of triglycerides led to a 32 percent increase in
cardiovascular risk in men and 76 percent increased risk in women.(2)
These results clearly challenge the emphasis that has been placed on
total cholesterol and LDL cholesterol. One study showed that among
12,500 men in Sweden, the lower the triglyceride level, the lower the
incidence of myocardial infarctions (MI). Even in the group with the
highest cholesterol level, which averaged 245 mg/dl, only 11
individuals with triglyceride levels less than 100 mg/dl had MIs,
compared to 97 individuals who had triglycerides greater than 184
All 16 of the other studies also confirmed elevated triglycerides as a
major risk factor and most showed that elevated LDL cholesterol levels,
when combined with triglyceride elevations, increased cardiovascular
Perhaps the most startling study was led by J. M. Gaziano at Harvard
Medical School.(4) Subjects with the highest ratio of triglyceride to
HDL had a 16-fold greater incidence of coronary events than those with
the lowest ratio. Gaziano's study, as well as the other studies
mentioned above, lends support to the idea that elevated levels of
triglycerides and low HDLs are also associated with hyperinsulinism.
Questioning the Wisdom of Low-Fat Diets for Everyone
For those who
have high triglycerides and low HDL, an appropriate question would be:
Is the low-fat, high-carbohydrate diet recommended by the American
Heart Association and the National Cholesterol Education Program the
best option? The results from numerous clinical studies would suggest
not. Studies comparing a low-fat diet that is comprised of 60 percent
carbohydrate with diets based on fewer carbohydrate show that
triglyceride levels rise significantly when carbohydrate content is
greater. (5-6). It is unfortunate that there are no studies comparing
lower levels of carbohydrate intake. It is highly likely they would
show a correlation between lower carbohydrate content and lower
A 1966 study by P.K. Reissell at Harvard demonstrated that a diet
containing only 26 grams of carbohydrate produced a greater than 70
percent drop in triglycerides in people whose original triglycerides
count exceeded 500 mg. (7) (With such a severe restriction of
carbohydrate intake, stored body fat becomes the body's primary fuel
source.) In the study, triglyceride levels were dramatically lowered.
A recent study on obese adolescents comparing a low-calorie diet with
an unlimited calorie, controlled carbohydrate eating plan showed a
greater than 50 percent average drop in triglycerides for individuals
on the controlled carb plan and a 10 percent drop for those on the
control low-fat diet.(8)
A Swedish study (3) that found that triglyceride levels below 100mg/dl
protected against coronary events was strongly confirmed by M. Miller's
study in Baltimore showing that the lowest group, those whose
triglycerides were below 100, had 2-1/2 times the protection from
coronary events than did the other three groups.(9)
The Role of a Controlled Carbohydrate Program
For years, it has been
an assumption that a nutrition plan primarily composed of protein and
fat has an adverse effect on blood chemistry. Amazingly, however, there
have been virtually no published studies confirming such results when
the diet was low enough in carbohydrate to cause the body to burn
stored fat as fuel. All of the studies indicating that dietary fat
creates lipid abnormalities were done with diets that also contain high
amounts of carbohydrate.
All studies where carbohydrates comprise less than 20% of the calories
have shown a drop in average total cholesterol and triglyceride levels.
1. National Health and Nutrition Examination Survey (NHANES) 3, 1988-94, CDC NCHF and the American Heart Association.
2. Austin, M.A., Hokanson, J.E., Edwards, K.L.,
"Hypertriglyceridemia as a Cardiovascular Risk Factor, " The American
Journal of Cardiology, 81(4A), 1998, pages 7B-12B.
3. Stavenow, L., Kjellström, T., "Influence of Serum Triglyceride
Levels on the Risk for Myocardial Infarction in 12,510 Middle Aged
Males: Interaction With Serum Cholesterol," Atherosclerosis, 147, 1999,
4. Gaziano, J.M., Hennekens, C.H., O'Donnell, C.J., et al., "Fasting
Triglycerides, High-Density Lipoprotein, and Risk of Myocardial
Infarction," Circulation, 96(8), 1997, pages 2520-2525.
5. Abbasi, F., McLaughlin, T., Lamendola, C., et al., "High
Carbohydrate Diets, Triglyceride-Rich Lipoproteins, and Coronary Heart
Disease Risk," The American Journal of Cardiology, 85, 2000, pages
6. McLaughlin, T., Abbasi, F., Lamendola, C., et al.,
"Carbohydrate-Induced Hypertriglyceridemia: An Insight Into the Link
Between Plasma Insulin and Triglyceride Concentrations," Journal of
Clinical Endocrinology and Metabolism, 85(9), 2000, pages 3085-3088.
7. Reissell, P.K., Mandella, P.A., Poon-King, T.M.W., et al.,
"Treatment of Hypertriglyceridemia," The American Journal of Clinical
Nutrition, 19, 1966, pages 84-98.
8. Sondike, S.B., Copperman, N.M., Jacobson, M.S., "Low Carbohydrate
Dieting Increases Weight Loss but not Cardiovascular Risk in Obese
Adolescents: A Randomized Controlled Trial," Journal of Adolescent
Health, 26, 2000, page 91.
9. Miller, M., Seidler, A., Moalemi, A., et al., "Normal
Triglyceride Levels and Coronary Artery Disease Events: The Baltimore
Coronary Observational Long-Term Study," Journal of the American
College of Cardiology, 31(6), 1998, pages 1252-1257.
10. Yancy, W. S., Bakst, R., Bryson, W., et al., "Effects of a
Very-Low-Carbohydrate Diet Program Compared With a Low-Fat,
Low-Cholesterol, Reduced Calorie Diet," October 7, 2001, Abstract of
the North American Association for the Study of Obesity Annual Meeting,
Quebec City, Canada.
11. Reed, T., Shakir, K.M.M., Harari, A.E., et al., "High-Fat,
Low-Carbohydrate Diet Improves Symptoms of Postprandial Hypoglycemia,"
June, 2000, Abstract of the 81st Annual Meeting of the Endocrine
Society, Toronto, Canada.