Nutritional Pearls: Is All Saturated Fat Bad?

Rosanne is a 63-year-old overweight woman who is concerned about her cholesterol levels. After doing some research on the Internet, she has decided to try to cut out all saturated fat from her diet. She questions whether this is her best option or if you have a different recommendation.

How would you advise your patient?
(Answer and discussion on next page)

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Answer: High-quality food sources, eaten in moderate amounts, are the best option for a healthy diet.

The big news in nutrition is that not all saturated fat is bad for you. Two studies looked at different types of saturated fat: one discussed very-long-chain saturated fatty acids¹ (a certain type of saturated fat), and another looked at the risk of diabetes² associated with greater intake of high-fat dairy products and higher-fat unprocessed meats.

The latter, while a long-term study, relied on the participants to accurately report their diets—then assumed that their diets would remain the same throughout the study. While it's reasonable to believe that people tend to eat about the same things over time as a research method it is not nearly as powerful as, say, yearly dietary questionnaires. Nor is it nearly as powerful as simply providing all of the participants' food for a period of time. That's quite expensive, however, and of necessity that type of research is usually limited to small groups of subjects, as in today's study.
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The Research

A team in Denmark recruited 14 overweight, postmenopausal women to participate in their feeding study. Each participant was provided with all meals and snacks for 2 weeks, in amounts designed to maintain their body weight. They were randomly assigned to 1 of 3 types of diets. Two of the diets were higher in saturated fat, while a third diet was lower in fat, as follows:

• A cheese diet, in which they consumed 36% of their energy from fats (half of that in saturated fat), 49% of their energy from carbohydrates, and 15% from protein. Half of the fats came from high-fat cheese.
• A meat diet, with 36% of energy from fat (also half of that in saturated fat), 49% of energy from carbohydrates, and 15% from protein. Half of the fats came from high-fat processed and unprocessed meats.
• A carb (low-fat) diet, with 23% of energy from fat (also half in saturated fat), 60% of energy from carbohydrates, and 15% from protein. This diet did not include any dairy products but did include lean meats.

The Results

After 2 weeks (known to be the amount of time to see dietary changes in cholesterol levels), the participants showed no change in their weight, waist or hip circumference, or blood pressure. Those who followed the cheese diet improved their HDL cholesterol (the good cholesterol) by 5% over the (low-fat) carb diet, while those on the meat diet improved their HDL by 8% over the carb diet. There were otherwise no significant differences between the 3 diets in total cholesterol or LDL cholesterol (the bad cholesterol).

What’s The “Take Home”?

One thing of concern is that the researchers do not specify the types of meat consumed in the meat diet. It is simply described as "high-fat processed and unprocessed meats," although the study does mention beef and pork. By comparison, the authors describe the cheese diet as including half Danbo cheese (a popular local cheese containing 27% fat by weight) and half cheddar (33% fat by weight).

Another limitation, as I mentioned, is the relatively short duration of the study: While 2 weeks is enough time to see the types of changes the researchers were investigating, a longer term study with more participants would provide more insight into the effects of the saturated fats from the respective specific sources.

What we can conclude from this study is that demonizing a particular nutrient—or even a particular food—is not the answer. High-quality food sources, eaten in moderate amounts, are the most reasonable, and the most personally sustainable, solution to a healthy diet.

Reference:
1. Food sources of fat may clarify the inconsistent role of dietary fat intake for incidence of type 2 diabetes. Am J Clin Nutr. 2015;101(5):1065-1080
2. Plasma phospholipid very-long-chain saturated fatty acids and incident diabetes in older adults: the Cardiovascular Health Study. Am J Clin Nutr. 2015;101(5):1047-1054
3. Diets with high-fat cheese, high-fat meat, or carbohydrate on cardiovascular risk markers in overweight postmenopausal women: a randomized crossover trial. Am J Clin Nutr. 2015;102:573-581