Despite all the research to the contrary, you probably still run into people who, when the topic of Atkins comes up in conversation, say: “I could never do Atkins because it allows saturated fat. I already have high cholesterol.” This mindset belongs to a generation that grew up with the message that eating eggs, meat and shellfish raises your cholesterol. (They also were led to believe that margarine is a better dietary choice than butter.) For decades, it has been pounded into their heads that foods containing saturated fat raise cholesterol and the risk of heart disease. It takes time to change such a mindset, but it happens. Just think: Five hundred years ago people were convinced the world was flat!
Let’s look at the two myths about the waxy substance known as cholesterol that fuel the misconception that Atkins is unhealthy.
Myth 1: Foods high in cholesterol raise your blood cholesterol.
Your dietary intake of cholesterol determines the level of cholesterol in your blood, so cholesterol could muck up the works by clogging blood vessels. For this reason, we were all advised that consuming less dietary cholesterol would keep blood cholesterol under control.
Reality: It is commonly accepted in the medical community that the majority of the cholesterol that ends up in your blood is produced in your liver; only about 25 percent is absorbed from food1. This means that there is not a significant relationship between the amount of cholesterol a person consumes and their blood-cholesterol levels. The advice to avoid high-cholesterol foods has been moderated and with good reason. Egg yolks, for example, contain a lot of cholesterol, but they also are rich in important nutrients that may lower heart-disease risk, such as vitamins D and B12, riboflavin and folate. Shrimp and lobster, also notorious for high cholesterol contents, contain heart-healthy omega-3 fatty acids and are rich in selenium and vitamin B12. Consuming a diet made up of nutrient-dense, whole foods and maintaining a physically active lifestyle are the best things you can do to keep cholesterol levels in check.
Myth 2: Avoid foods that contain saturated fat because eating them raises your cholesterol and increases your risk of cardiovascular disease.
This common nutritional advice is true for people who eat a high-carbohydrate diet. Studies showing a link between saturated fat and higher cholesterol levels have examined people eating the typical American high-carb diet.
Reality: In the context of a low-carbohydrate program, a number of recent studies conducted on people doing Atkins have demonstrated that a diet containing saturated fat can have positive effects on cholesterol profiles2,3.
Another little-known fact: An exhaustive body of research on dietary fat shows that the total percentage of fat in the diet has no bearing on health. In two large, long-term studies conducted by Harvard researchers, people with the highest intake of fat were no more likely to get heart disease or even to gain weight than the people with the lowest intake4,5.
What is important is consuming a variety of natural fats, controlling carbs and avoiding manufactured Trans fats. Here’s why:
• Unsaturated fats—which come from fish, olives, nuts and vegetables—lower LDL (“bad”) cholesterol and raise HDL (“good”) cholesterol.
• Saturated fats, which come primarily from animal products, can raise both HDL and LDL cholesterol, but in the context of a low-carbohydrate diet, effects on cholesterol levels are positive. (See “Is All Saturated Fat the Same?”)
• Controlling carbohydrates reduces triglycerides, a third type of lipid (fat), which is an independent risk factor for heart disease.
• Manmade trans fats—found in most margarines, baked goods, fried foods, crackers, chips and many packaged foods—raise LDL cholesterol and lower HDL cholesterol.
Is All Saturated Fat the Same?
There are four types of saturated fatty acids, which can have varying effects on cardiovascular risk factors. The following types are listed in the order in which they impact LDL cholesterol.
• Stearic acid is considered neutral, having no impact on LDL
• Palmitic acid
• Myristic acid
• Lauric acid is the most likely to increase LDL cholesterol
Many fatty foods are actually combinations of both saturated and unsaturated fatty acids. Even steak contains less than 50 percent saturated fat; the rest is mono- or polyunsaturated fats. Further, the proportion of the various saturated-fat subgroups differs from food to food. Whole foods such as red meat, butter, cheese, poultry, eggs, pork and fish are composed primarily of palmitic and stearic saturated fatty acids and contain small amounts of lauric or myristic acids. Processed foods, on the other hand, contain more of the myristic and lauric acids. Recent studies have shown that lipid profiles improve in people following a low-carbohydrate diet6,7. This is likely because the saturated fats in the foods commonly consumed contain predominately palmitic and stearic fatty acids.
The next time someone asks, “Aren’t you worried about your cholesterol doing Atkins?” be prepared to tell what you know. If he still seems skeptical, remind him that the world was never flat. Then send them to this Web site.
Selected References
1. Harvard School of Public Health, “Fats & Cholesterol.” Available at http://www.hsph.harvard.edu/nutritionsource/fats.html; accessed April 19, 2005.
2. Vernon, M.C., Kueser, B., Transue, M., et al., “Clinical Experience of a Carbohydrate-Restricted Diet for the Metabolic Syndrome.” Metabolic Syndrome and Related Disorders, 2(3), 2004, pages 180-186.
3. Boden, G., Sargrad, K., Homko, C., et al., “Effect of a Low-Carbohydrate Diet on Appetite, Blood Glucose Levels, and Insulin Resistance in Obese Patients with Type 2 Diabetes.” Annals of Internal Medicine, 142(6), 2005, pages 403-411.
4. Hu, F.B., Stampfer, M.J., Manson, J.E., et al., “Dietary Fat Intake and the Risk of Coronary Heart Disease in Women.” New England Journal of Medicine, 1997, 337(21), pages 1491-1499.
5. Ascherio, A., Rimm, E.B., Giovannucci, E.L., et al., “Dietary Fat and Risk of Coronary Heart Disease in Men: Cohort Follow Up Study in the United States.” British Medical Journal, 313(7049), 1996, pages 84-90.
6. Westman, E.C., Yancy, W.S., Edman, J.S., et al., “Effect of 6-Month Adherence to a Very Low Carbohydrate Diet Program.” American Journal of Medicine, 113(1), 2002, pages 30-36.
7. Hickey, J.T., Hickey, L., Yancy, W.S., et al., “Clinical Use of a Carbohydrate-Restricted Diet to Treat the Dyslipidemia of the Metabolic Syndrome.” Metabolic Syndrome and Related Disorders, 2003, 1(3), pages 227-232.
