A new study in The Journal of Nutrition concluded that replacing carbohydrates with monounsaturated fats may be beneficial for heart health, whereas the opposite was found for saturated fats.
Cardiovascular disease remains a leading cause of death in the United States and many regions around the globe, and ongoing research continues to examine what constitutes an optimal dietary pattern in this regard. Guidance on this topic has fluctuated over the years, making it difficult for health professionals to provide evidence-based advice. Although these ever-changing recommendations may appear to indicate that little is known about the association between diet and cardiovascular disease, in reality, they reflect an evolving understanding of the complex relationships at play. For example, for decades research has focused on finding ways to increase levels of high-density lipoprotein (HDL) cholesterol and reduce low-density lipoprotein (LDL) cholesterol. However, a more current understanding has shifted the focus to increasing HDL cholesterol and decreasing all forms of non-HDL cholesterol, rather than just LDL cholesterol. Little research has evaluated which dietary patterns are associated with lowering non-HDL cholesterol levels.
This question was recently studied by an international group of scientists who utilized diet and health data garnered from 8 studies carried out previously in Europe. Their study, which was conducted as part of the Nutritional Phenotype Assessment and Data Sharing Initiative (ENPADSI), evaluated whether replacing dietary carbohydrates with various types of dietary fats was associated with levels of HDL and non-HDL cholesterol (including that found in LDL). A total of 5919 teens and adults were included in their analysis.
Results indicated that replacing 5% of calories from carbohydrates with total fats or monounsaturated fats (such as those found in olive oil and canola oil) was associated with higher HDL cholesterol – but only in males. Replacing calories from carbohydrates with saturated fats (such as those found in tropical oils and animal-source foods) was associated with an increase in non-HDL cholesterol – a response that would suggest a negative impact on heart health. Conversely, replacing carbohydrates with polyunsaturated fat (such as those found in fish and most vegetable oils) was not associated with a shift in HDL cholesterol. The researchers concluded that the replacement of dietary carbohydrates with fats had favorable effects on cholesterol concentrations when fats were consumed in their monounsaturated form, but not when they are present as saturated fats.
An accompanying commentary by Drs. Bruce Griffin (University of Surrey) and Julie Lovegrove (University of Reading) agrees that this study provides indirect evidence of a potential benefit of replacing dietary carbohydrates with monounsaturated fat, whereas there may be a risk associated with replacing carbohydrates with saturated fats. However, they point out that this study cannot provide definitive evidence because it was observational (not interventional) in nature. In addition, they urge a more thorough examination of the many types of fats, such as omega-3 vs. omega-6, as well as the many sources of carbohydrates, such as whole-grain vs. refined.
References
Pinart M, Jeran S, Boeing H, et al. Maternal dietary macronutrient composition in relation to circulating HDL and non-HDL cholesterol: A federated individual-level analysis of cross-sectional data from adolescents and adults in 8 European studies. The Journal of Nutrition, Volume 151, Issue 8, August 2021, Pages 2317–2329, https://doi.org/10.1093/jn/nxab077.
Griffin BA, Lovegrove JA. Evidence for beneficial associations between isoenergetic macronutrient exchanges and serum non-HDL cholesterol, a measure of all circulating atherogenic, apoB-containing lipoproteins. The Journal of Nutrition, Volume 151, Issue 8, August 2021, Pages 2096–2098, https://doi.org/10.1093/jn/nxab127.
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