Dairy foods have long been hailed for their nutritional richness, although researchers are still debating over the metabolic effects of milk fats. Many dietary recommendations advocate fat-free or low-fat dairy options due to concerns over the possible adverse effects of saturated fatty acids (SFAs) on cholesterol levels. But now, a review of recent research has cast doubt on this conventional thinking.
A literature review conducted by researchers in Mexico compiles evidence on the metabolic effects of milk fatty acids from clinical and basic research studies, shedding light on their relationship with metabolic disorders and gut microbiota composition [1].
The evidence suggests that milk fatty acids aren’t directly linked to cardiometabolic risk, and calls into question whether dietary recommendations for low-fat dairy foods are indeed necessary for preventing obesity and cardiometabolic disease.
What are the fatty acids in milk and dairy foods?
- Milk fat is made up of saturated (62%), mono-unsaturated (29%) and poly-unsaturated (4%) fatty acids [2]
- Milk fats are mainly stored as fat globules surrounded by a membrane known as the milk fat globule membrane (MFGM) [2]
- The main components of the MFGM are triglycerides (95.8%), with lower proportions of free fatty acids, mono- and di-glycerides, phospholipids, and cholesterol [3]
- Milk triglycerides contain nearly 400 different fatty acids, which have a wide range of metabolic effects depending on their chain length and level of saturation [3]
- The main fatty acids present in milk and dairy foods include palmitic, stearic, oleic, and myristic acid.
Most dairy fats have effects that may help prevent adiposity
While some milk fatty acids are associated with increased adiposity, most exert anti-fat effects that may help to prevent weight gain, the research has revealed.
- Several clinical studies have shown that some medium- and long-chain fatty acids found in dairy foods are associated with reduced body fat accumulation.
- Pre-clinical studies suggest that some milk fatty acids may exert anti-fat effects through modifying lipid metabolism in adipose tissue [4].
The overall effect of milk fatty acids on weight gain may depend on the balance between them in different dairy foods. Further clinical research is needed to understand the possible mechanisms by which dairy fats may contribute to decreased adiposity, the researchers suggest.
Eating full-fat dairy foods may be associated with a reduced risk of diabetes
The researchers discovered that eating full-fat dairy foods has been associated with a reduced risk of type 2 diabetes (T2D) progression in some studies, including a large multi-national study in which participants were followed for a median of 9 years [5] although not all studies have confirmed these findings.*
A large observational study suggested that dairy fat was associated with improved glucose tolerance via hepatic and systemic insulin sensitivity [6].
Pre-clinical studies also suggest that some short-chain fatty acids found in dairy foods can improve insulin sensitivity, increase β-cell function, and reduce inflammation.
Evidence suggests that even though some milk fatty acids are associated with insulin resistance, this does not lead to an increased risk of T2D when they are consumed within dairy foods.
Dairy foods may have neutral or beneficial effects on cardiovascular disease (CVD) risk
Concerns over the effects of full-fat dairy foods on CVD risk arose from historical data suggesting that saturated fatty acids are associated with increased cholesterol levels. However, researchers found that recent studies support the idea that dairy foods have a neutral or beneficial association with CVD outcomes.
Results of several randomised controlled trials show that consumption of SFAs from dairy foods can adversely increase low-density lipoprotein cholesterol (LDL-C).
But the literature suggests that LDL-C is not a good predictor or cause of CVD risk, raising doubt over the cautious approach taken towards dairy fats. [7].
Further analysis reveals that eating dairy foods high in SFAs can boost levels of high-density lipoprotein cholesterol (HDL-C) and has no adverse effects on other CVD markers including blood pressure, inflammation, and vascular function [8].
It appears that dairy fat as a whole, as well as individual fatty acids, have either neutral or mixed effects on atherogenesis, lipid profiles and inflammation, according to the researchers.
What about the role of the gut microbiota in metabolic health?
The researchers also examined the relationship between consumption of milk fatty acids and the gut microbiota. They found that eating dairy food is associated with beneficial changes to the composition of the gut microbiota.
- Clinical studies show that dairy consumption promotes the abundance of healthy gut bacteria, such as Bifidobacterium, which are associated with anti-inflammatory properties and a lower risk of T2D.
- The gut microbiota can also modify milk fatty acids, producing metabolites that may benefit metabolic health.
It is important to consider the metabolic health effects of the entire food matrix from which milk fatty acids are consumed. For instance, interactions between the nutrients within dairy products can change the effects of individual fatty acids on the metabolism, altering their overall cardiometabolic risk profile [9].
“Fatty acids contained in dairy products have neutral, mixed or even positive effects on metabolic diseases (overweight, obesity, T2D, CVD and atherosclerosis) by modifying risk factors such as insulin resistance, and the expression of genes related to inflammation and dyslipidaemia.” – Muñoz-Alvarez KY, et al., 2024
Studies on the large-scale Prospective Urban Rural Epidemiology (PURE) add to the growing body of evidence pointing to the need to re-evaluate the guidelines that recommend avoiding whole fat dairy products.
It concludes that a diet comprising higher amounts of fruit, vegetables, nuts, legumes, fish, and whole-fat dairy is associated with lower CVD and mortality in all world regions (10).
Specifically, it concludes that higher intake of whole fat (but not low fat) dairy was associated with a lower prevalence of metabolic diseases and most of its component factors, and with a lower incidence of hypertension and diabetes (5).
*On March 1st, 2024, the U.S. Food and Drug Administration (FDA) has approved a qualified health claim regarding the consumption of yogurt and reduced risk of type 2 diabetes (T2D) : “Eating yogurt regularly, at least 2 cups (3 servings) per week, may reduce the risk of type 2 diabetes according to limited scientific evidence.”
