Why is it “suddenly” okay to consume in moderation such things as butter and Malaysian palm oil? For decades, science recommended that low-fat and non-fat foods should dominate the American palate. The government’s 2015 Dietary Guidelines for Americans (DGA) contained several recommendations supporting a shift that “okays” tropical oils and saturated fats.
“Based on an extensive review of the science, the DGA noted that total dietary fat and dietary cholesterol aren’t health concerns if you’re healthy,” explains Roger Clemens, DrPH, who has participated in the DGA process. “They even said that low-fat diets may not be the solution if you suffer from any number of chronic diseases including cardiovascular disease, diabetes, hypertension and obesity.” Instead, the DGA urges you to focus on the type of fat you’re eating. Yet, it is important to remember that for some individuals, high-saturated fat diets may not be appropriate.
While the Guidelines still caution you to limit saturated fat, the scientific evidence isn’t as strong as you might think. Extensive reviews and meta-analyses have called into question much of what many assumed to be consistent and true about saturated fat and our health.
Grading – or ranking – what we know
The Dietary Guidelines Committee ranks – or grades – the scientific research based on five criteria:
- Risk of bias. What variables did the researchers choose to include/exclude, for example, in their study design?
- Quantity of studies. How much research has been done on this subject?
- Consistency of studies. Were the conclusions repeatable from one study to the next?
- Impact of studies. How relevant are the study conclusions?
- Generalizability of the studies. Can we draw some general conclusions applicable to the American public?
Clemens explains: “Using these criteria, we then look at the strength of the evidence: strong, moderate, limited or not assignable. Strong evidence is substantiated by large, high quality and/or consistent evidence that directly addresses the question. There’s a high degree of certainty that a strong conclusion is unlikely to change even if new evidence emerges.”
Dietary cholesterol got downgraded!
In 1961, researcher Ancel Keys asserted there was strong evidence that dietary cholesterol increased risk of cardiovascular disease. That conclusion was supported by the National Institutes of Health in 1984.
But in 2015, the DGA advised that dietary cholesterol does not impact serum cholesterol levels or pose a health risk. “So the once strong evidence against dietary cholesterol was downgraded to not assignable,” says Clemens.
What the science is really telling us about dietary fats
About 15 years ago, researchers found that the risk of heart disease was reduced by 30 to 40 percent when study participants replaced 5% of the saturated fat in their diets with monounsaturated and polyunsaturated fats. But other researchers found that swapping that 5% of saturated fat in their diets with carbohydrates raised cardiovascular disease risk by nearly 15 percent. So swapping fats for carbs may not be a good move.
It’s also important to understand that not all saturated oils and fats have the same components. Different types of fatty acids – including lauric, palmitic, stearic and myristic – are innately present in different ratios in foods. And other studies have determined that replacing carbohydrates with the various types of saturated fatty acids affected blood cholesterol levels differently.
Genetic differences and gender have also been found to play a role in how low- and high-fat diets modulate cardiovascular disease risk factors. Also interesting, the greatest changes between high- and low-fat diets occurred among men versus among women.
Clemens comments that, “While the 2015 DGA stated there was strong, consistent evidence from randomized control clinical studies to advise consumers to limit their dietary saturated fat intake to 10 percent, this position assumes that all saturated fats have adverse health consequences. A closer examination of the studies indicated that saturated fat intake is not necessarily associated with an increased risk of heart disease or stroke.”
Tropical oils may also have some health benefits. Malaysian sustainable palm oil has a unique fatty acid profile, plus natural antioxidants such as vitamin E tocotrienols and carotenoids. Palm oil is also naturally trans-fat free.
What this means
There are epidemiologic data that do not support the position that saturated fats represent a risk to the development of cardiovascular disease. There are also data that suggest including certain saturated fats in your diet may reduce your stroke risk. Your genetic factors, lifestyle and life stage may be critical in how your body responds to what you eat.
Despite these controversial findings, consuming saturated fat as well as monounsaturated and polyunsaturated fats, may contribute to improved health outcomes and reduced risks of developing a spectrum of diseases such as heart disease, stroke and diabetes.