Even nutritionists and other healthcare professionals may be feeling a little dizzy by the emerging science related to saturated fats and heart disease. After decades of believing that one contributed to the other, there’s been an abrupt shift.
An epidemiological link between dietary fats, serum cholesterol and heart disease was announced back in the 1960s. The reaction to what’s now recognized as weak evidence spiraled. By 1984, the National Institutes of Health was advising Americans to reduce their total dietary fat intake to 30 percent, and their saturated fat intake to less than 10 percent of their total calories.
Fast forward to 2015, when the USDA’s Scientific Report of the 2015 Dietary Guidelines Advisory Committee, said: “Available evidence shows no appreciable relationship between consumption of dietary cholesterol and serum cholesterol.” Many people still haven’t gotten the word – or do not yet believe the committee’s recommendation – that cholesterol is not a nutrient of concern for overconsumption. The most recent evidence indicates you can consume a reasonable level of saturated fats and it may not negatively impact your cholesterol levels.
About the Author
Roger Clemens, DrPH, is adjunct professor of pharmacology and pharmaceutical sciences within the University of Southern California School of Pharmacy, International Center for Regulatory Science. He served on the USDA 2010 Dietary Guidelines Advisory Committee with primary responsibilities in food safety, and dietary lipids and health, and earlier was a scientific advisor for Nestlé USA for more than 21 years. He discussed this topic at the recent Palm International Nutra-Cosmeceutical Conference.
Why did it took so long to unravel the inaccurate conclusions?
Weaker evidence includes expert opinions and case studies. Common words such as "association," "related" and "relative risk" imply strength, yet upon review, the work may be quite weak. Importantly, clinical trials among small populations do not necessarily translate to the total population.
Much of the current evidence relies on meta-analyses and systematic reviews of the clinical research, which can take years to develop. That’s the evidence that is now emerging related to the fats in our diets. And it’s changing our thinking about saturated fats, serum cholesterol and heart health.
There’s now strong evidence that replacing saturated fat with carbohydrates, a hallmark of low-fat diets, does not necessarily lower the risk of cardiovascular disease. Replacing saturated fats with carbohydrates reduces total and LDL-C cholesterol, but they may significantly increase triglycerides and reduce the good cholesterol, HDL-C.
Further, a meta-analysis published last year in the Annals of Internal Medicine concluded that current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.
Low-fat diets don’t even produce weight loss. The Women’s Health Initiative followed more than 20,000 women on low-fat diets for an average of seven years. They weighed only one pound less than the controls, and they had no improvements in heart health.
So how should we be eating?
Even single foods often contain a complex nutrient mix. Judging a food or an individual’s diet as harmful because it contains more saturated fatty acids, or beneficial because it contains less, is intrinsically flawed. The emphasis should be on optimizing the types of dietary fat we’re eating, not on reducing total fat.
As we look forward to food and health, the real emphasis should be on the dietary patterns that are culturally appropriate.
As recently as 2010, it has been acknowledged that the stearic acid found in Malaysian certified-sustainable palm fruit oil is not known to raise LDL cholesterol. In fact, evidence suggests stearic acid should not even be categorized with known cholesterol-raising fats.
While diet is linked to health, there is a reason why there’s so much confusion about what to eat. The answer may be as unique as you are. Variations in your genetics, lifestyle and life stage can all influence how your body responds to your diet.
The bottom-line message: Consumers should concentrate on eating a variety of foods, instead of getting their nutrients from a minimal number of sources. And they should weigh news about diet and health carefully, understanding that it can take years for the strongest evidence to emerge.