“Dietary advice about single nutrients that fails to consider dietary context is problematic,” as macronutrients share food sources and are difficult to isolate without adding other nutrients as replacements that can impact health outcomes, Canadian researchers Russell de Souza and Sonia Anand, argue in the editorial.
They explain that while studies of individual nutrients are essential to ensure nutritional adequacy or prevent deficiencies, determining an optimal macronutrient balance to prevent chronic diseases is more nuanced.
Thus, they argue, encouraging people to follow healthy dietary patterns, as advocated by the 2015 US Dietary Guidelines Advisory Committee “might provide more appropriate information to guide food choices,” and have a larger positive impact on heart disease rates.
Cutting saturated fat could cut heart disease risk
They base this conclusion in part on analysis of two large US longitudinal cohort studies published the same day in The BMJ.
The study, conducted by researchers at Harvard University, looked again at the potential impact of saturated fat consumption on heart disease and found a higher intake of major saturated fatty acids was directly associated with an increased risk of coronary heart disease.
After reviewing data from the Nurses’ Health Study from 1982-2012 and the Health Professionals Follow-Up study from 1986-2010, the researchers identified people who consumed 5% more long-chain saturated fats, such as found in hard cheeses, whole milk, butter, beef and chocolate, were 25% more likely to develop coronary heart disease than those who consumed less.
Conversely, their research also found a reduction of saturated fat consumption by as little as 1% of daily energy is associated with a 4-8% reduced risk of coronary heart disease.
What replaces saturated fat matters
But there is a catch: These benefits were observed only when replaced with polyunsaturated fats, whole grain carbohydrates or plant proteins -- not the sugars and starches that many Americans reached for to fill the void the first time public health advocates urged a reduction in saturated fat.
This is notable because those who argue for eating butter and reversing years of dietary advice, base their beliefs partly on other research that found no association between reducing saturated fat intake and risk of cardiovascular disease when the comparison nutrient was the choice of carbohydrate, according to the editorial.
Other research also showed that those who consumed more saturated fat but had lower risk also consumed less refined sugar and starch.
However, de Souza and Anand note in the editorial, “the devil is in the details,” as starch and sugar “might increase the risk of coronary heart disease,” and therefore adding or removing them might counter-balance the impact of removing or adding saturated fat in the diet.
That is why the current study specifically looks at polyunsaturated fat, whole grains and plant-protein as comparative nutrients.
It also found that all of these macronutrients were associated with different levels of reduced risk -- driving home the message that different macronutrients react differently with each other and in the body, and therefore a whole dietary pattern approach is more beneficial.