In the US, our kids can't get full-fat milk in public school. There is plenty of non-fat chocolate milk, but there is no full-fat milk. We can all say "thank you" to the dietary guidelines for that policy. One could presume that to make such a sweeping and penetrating recommendation, there must be conclusive evidence documenting the harm of full-fat dairy. That is far from the truth.
In fact, there is a mounting body of evidence that dairy consumption, even full-fat dairy, is not harmful and may even be beneficial for health. To be fair, these studies tend to be weak, observational studies and suffer from confounding variables, healthy-user bias, food-frequency questionnaires, and other methodological short fallings. Yet, even weak evidence should be enough to call into question a guideline that has no higher quality evidence to back it.
Some of these studies, however, use blood levels of particular saturated fatty acids (that are defined based on the number of carbon (C) atoms) - specifically lauric acid (C12), myristic acid (C14), palmitic acid (C16), and stearic acid (C18). This method gives a more accurate estimate of fatty acid consumption because it is an objective measurement rather than an estimate based on subjective (and often inaccurate) food frequency questionnaires. However, food typically contains a combination of fatty acids, so the blood measurements cannot be directly tied to the source, dairy or meat consumption, with 100% accuracy.
The most recent study in The International Journal of Cardiology evaluated data from two different studies, one from the UK and one from Denmark. They included over 77,000 subjects and lasted between 13 and 18 years. The investigators tried to correlate blood levels of different saturated fatty acids and risk of heart attacks. They concluded that higher levels of shorter-chain saturated fatty acids, lauric and myristic acid, are associated with a decreased risk of cardiovascular disease. They also concluded the longer-chain saturated fatty acids, palmitic and stearic either had no effect (in a UK population) or were associated with a very slight increased risk (in a Danish population) of cardiovascular disease versus participants who were eating more plant proteins.
To their credit, the authors also noted the shortcomings in the data interpretation:
Because of the high correlations between the saturated fatty acids, observational cohort studies alone will not suffice in answering the question of whether individual saturated fatty acids have different associations with myocardial infarction or coronary heart disease. Also in our study, high correlations between several saturated fatty acid subtypes exist, which made it unclear whether the observed associations in our study pertain to all these saturated fatty acids, or represent the association of one of them.
This most recent study adds to a growing collection of data showing saturated fatty acids and dairy intake are not as harmful as frequently reported.
A recent evaluation of the PURE study showed either a beneficial or neutral association between dairy intake and both cardiovascular events and mortality.
Also just last year, an evaluation of 16 cohort studies showed an association between higher blood levels of fatty acids pentadecanoic acid and heptadecanoic acid which are more likely found in dairy, and lower risk of diabetes, cardiovascular disease and stroke.
This type of debate is becoming common. Saturate-fat consumption can increase LDL cholesterol and is therefore considered "dangerous" even without incriminating outcome data to confirm risk of harm. Unfortunately, this simplistic thinking ignores the fact that saturated fats also increase HDL and can lower triglycerides, thus potentially improving important heart-health ratios such as Apo B/Apo A1 ratio, total cholesterol/HDL ratio, and others.
The emergence of this new data showing that saturated fatty acids and dairy fats have either a neutral or beneficial association with health outcomes is a welcome addition. This data will help us break free from overly simplistic thinking and understand the true impact of fat on our health.
Personally, I'm sending my kids to school with a thermos for their full-fat milk.
Thanks for reading,
Bret Scher, MD FACC
