International scientific team faults WHO warning against saturated fat 08/19/2019
Science isn’t supposed to be a wrestling match, but things can quickly deteriorate in that direction.
One heated, ongoing debate focuses on two related pieces of conventional medical wisdom that have lately come under fire:
- Saturated fat is bad for cardiovascular health, and we eat too much.
- We should replace most dietary saturated fats with polyunsaturated fats.
Saturated fats abound in meats, poultry, and whole dairy foods, while only a few plant foods — such as coconut oil and cocoa powder or chocolate — contain significant amounts.
Several major studies have faulted the decades-long campaign against saturated fats, as well as advice to replace them with polyunsaturated omega-6 plant fats: see Vegetable Oils Debunked for Heart Disease, Major Study Exonerates Saturated Fat, and “Heart-Healthy” Omega-6 Oils? Evidence is Lacking.
Until recently, health authorities placed much less emphasis on replacing saturated fats with polyunsaturated omega-3 fats from seafood, versus omega-6 fats from vegetable oils.
That emphasis resulted in extremely excessive consumption of plant-source omega-6 fats and woeful under-consumption of omega-3s, of which seafood and fish oil are the best sources by far. (See the Omega-3/6 Balance page on our website, and the “Out of Balance” video posted there.)
Now, an international scientific team has fueled the debate with a sharp critique of draft World Health Organization (WHO) guidelines on saturated fats.
Let’s look at that paper, published in the British Medical Journal (BMJ), as well as a rebuttal also published in the BMJ.
WHO’s 2018 draft guidelines on saturated fat
The authors of the new paper were critiquing draft guidelines on saturated and trans fatty acids issued by the WHO in May of 2018.
The draft WHO guidelines — which echo most mainstream medical advice — are designed to reduce the risk of cardiovascular disease and related deaths.
Those WHO guidelines advise people who get more than 10% of their calories from saturated fats to replace the "excess" amounts with polyunsaturated fats and monounsaturated fats, of which these are the most common and abundant sources:
- Polyunsaturated omega-6 fats: nuts, seeds, vegetable oils (e.g., corn, soy, safflower, sunflower)
- Monounsaturated fats (mostly oleic acid): olive oil, canola oil, “high-oleic” sunflower and safflower oils, macadamia nut oil, and avocados
- Polyunsaturated omega-3 fats: wild fish (especially fatty species like salmon, albacore tuna, or sardines) and shellfish, dark leafy greens, walnuts, flaxseed, avocados, and omega-3-fortified foods (e.g., eggs or yogurt)
International team criticizes WHO guidelines
The authors of the new critique applaud the WHO’s advice to eliminate the man-made trans fatty acids produced when vegetable oils are partially hydrogenated to resist oxidation and rancidity.
However, they objected to the guideline that recommends limiting intake of all saturated fats to 10% of total calorie consumption, based on three basic criticisms (Astrup A et al. 2019).
Criticism #1: All saturated fats are not equal, and their dietary context matters
As the authors of the new paper wrote, “… this [WHO advice] fails to take into account considerable evidence that the health effects vary for different saturated fatty acids and that the composition of the food in which they are found is crucially important.”
Rather than testing the effects of whole-food sources of the major types of fat, most of the 84 trials relied on by the WHO tested the effect of isolated fats such as cocoa butter, olive oil, soybean oil, and butter.
As the WHO's critics said, different saturated fats have very different effects on people’s cholesterol profiles and their risks for coronary heart disease.
For example, a saturated fat called heptadecanoic acid is linked to a reduced risk for coronary heart disease.
And the WHO critics noted that diets featuring fairly large amounts of a diverse range of saturated fats have been linked to rises in larger, generally safe LDL cholesterol particles. (Small- and medium-size LDL, not large LDL cholesterol, are linked to cardiovascular disease.)
Accordingly, the noted that higher consumptions of a wide range of saturated fats may not raise the risk of cardiovascular disease to a significant extent.
The WHO's critics also pointed to the findings of the PURE study, which included more than 100,000 people. Those findings linked diets high in saturated fats to higher LDL cholesterol levels, higher/healthier levels of "good" HDL cholesterol, lower/healthier levels of triglycerides, and a lower/healthier ratio of apolipoprotein B to apolipoprotein A (two types of cholesterol "transporters").
Nor did the PURE study link diets relatively high in saturated fats to people’s risk for adverse cardiovascular events — e.g., heart attacks and heart-related deaths — except for linking such diets to a lower risk for stroke.
Importantly, as the WHO critics noted, the findings of the PURE study are supported by the results of at least three randomized clinical trials.
Criticism #2: Links between cholesterol and cardio risks aren’t as clear as claimed
As the WHO’s critics pointed out, the UN agency’s draft guidelines rest on a misleadingly oversimplified picture of the links between cholesterol profiles — such as the levels of LDL (“bad”) cholesterol or the ratio of total cholesterol to HDL (“good”) cholesterol — and cardiovascular risks.
Most of the 84 trials upon which the WHO relied used overall LDL cholesterol levels as a predictor for higher cardiovascular disease risk: a poorly justified presumption that, as the WHO's critics wrote, “could lead to erroneous conclusions”.
That's because — as noted above — different types of LDL cholesterol have very different effects on cardiovascular risk.
And, as we reported in the articles listed at the beginning of this article, LDL cholesterol levels aren't very reliable predictors for cardiovascular disease or heart-related death.
For example, the results of the famed Lyon Diet Heart Study linked Mediterranean-style diets to significant drops in the risk for major cardiovascular disease events (e.g., heart attacks) even though such diets did not tend to lower overall LDL cholesterol levels.
Likewise, two recent analyses of the large PREDIMED trial — which tested the effects of Mediterranean-style diets — concluded that overall LDL cholesterol levels are not good predictors of cardiovascular disease risk.
The WHO critics also mentioned a reanalysis of the Minnesota Coronary Experiment trial, which found that — although a test diet high in polyunsaturated fats produced a 13% greater reduction in total blood cholesterol than a test diet high in saturated fat — the polyunsaturated-fat-rich test diet didn’t reduce the short-term risk for heart attacks, stroke, or heart-related deaths.
Instead, that reanalysis of the Minnesota trial linked reductions in total blood cholesterol caused by the test diet high in polyunsaturated fats to higher risks for death. (Note: we covered that reanalysis in Vegetable Oils Debunked for Heart Disease.)
Criticism #3: Clinical trials aren’t necessarily the “gold standard” in this context
The authors of the WHO's draft guidelines excluded the huge amounts of evidence from epidemiological studies, arguing that the quality of their evidence is lower than the evidence from randomized clinical trials, which is generally true.
But the clinical trials they relied upon looked for the effects of isolated dietary fats on cholesterol profiles and other dubious “surrogate” markers for cardiovascular risk, not for their effects on cardiovascular health outcomes, which can take years or decades to develop.
Epidemiological studies are actually more valuable for examining links between dietary fats and long-term health outcomes, such as cardiovascular disease.
Rebuttal to WHO critics' paper appears weak
In a response to the new critique of the draft WHO guidelines, University of Sydney Emeritus Professor A. Stewart Truswell objected that the WHO critics had overlooked some key facts (Truswell AS 2019).
Professor Truswell said that the international team placed too much trust in epidemiological studies that haven't linked higher consumption of saturated fats to higher risks for cardiovascular disease.
His criticisms have some merit, but failed to recognize the weaknesses of many of the clinical studies upon which the WHO guidelines heavily depended.
Dr. Truswell noted that heart-related deaths in America and European countries fell between their peak in 1967-1968 and 1994, along with fairly steep declines in consumption of butter and red meat.
But, as Dr. Truswell acknowledged, those declines in heart-related deaths followed fast-growing use of statins, which reduce the risk for heart attacks and heart-related deaths.
Importantly, while statins lower total and LDL cholesterol levels, it's very likely that their cardiovascular benefits flow in large part from their anti-inflammatory effects (see “Statins and cholesterol aren’t the only options and factors”, below).
Oddly, one of the studies he referenced to support his comments actually undermines his position that saturated fats are the primary problem (Mozaffarian D et al. 2010).
The authors of that 2010 review of the clinical evidence noted that we can at most expect a 10% lower risk of coronary heart disease in return for replacing 5% of saturated fat calories with polyunsaturated fat calories.
As the review's authors wrote, this “… indicates a need for substantial policy focus on other dietary risk factors for coronary heart disease, in particular high consumption of salt and low consumption of seafood, whole grains, fruits, and vegetables.”
And the average American’s extremely high consumption of polyunsaturated omega-6 fats appears to promote weight gain, inflammation, and the many chronic conditions linked to inflammation, including cardiovascular disease: see the Omega-3/6 Balance page on our website, and the “Out of Balance” video posted there.
That problem is worsened by the average Americans' serious under-consumption of omega-3 fats, especially the anti-inflammatory omega-3 fats that abound only in seafood and fish oil (EPA and DHA), which are far safer than high-dose statin drugs, and bring many other health benefits.
Statins and cholesterol aren’t the only options and factors
When it comes to anti-inflammatory, triglyceride-lowering, and cholesterol-modifying effects — all of which can reduce cardiovascular risks — prescription statin drugs are a costly way to achieve them.
For more on that topic, see Statin Advice Called into Question, Value of Omega-3s Vindicated, Again, Yeasty Rice Rivals Statin Drugs, Statin Drug Beaten by Alternative Cholesterol Treatment, Switch to Fish Yields Statin-Like Benefits, Does Statins' SuperStar Status Make Sense?, and Omega-3s Seen Rivaling Statins at Reducing Risk of Death.
High doses of strong statin drugs (e.g., simvastatin, atorvastatin, or rosuvastatin) can reduce high blood levels of triglycerides — which rival unhealthful cholesterol profiles as a cardiovascular risk factor — by as much as 50%.
However, similar triglyceride-lowering effects can be achieved by fibrate drugs, niacin, and high, anti-inflammatory doses of omega-3 fatty acids from seafood (EPA and DHA).
What does this all mean?
The critics of the WHO guidelines make some very strong points.
Of course, this doesn’t mean that it’s smart to overdo foods rich in saturated fat, like bacon or butter — in part because diets very high in saturated fat are linked to higher risk for dementia.
Instead, the flaws in the WHO and other mainstream medical guidelines strongly suggest that you needn’t go out of your way to avoid foods that are relatively high in saturated fats.
Ironically, health authorities urged us to replace of most of the saturated fats in our diets with vegetable oils and with margarine, which is high in heart-attacking trans fatty acids.
That egregiously damaging error reminds us that it pays to question conventional wisdom!
- Astrup A, Bertram HC, Bonjour JP, de Groot LC, de Oliveira Otto MC, Feeney EL, Garg ML, Givens I, Kok FJ, Krauss RM, Lamarche B, Lecerf JM, Legrand P, McKinley M, Micha R, Michalski MC, Mozaffarian D, Soedamah-Muthu SS. WHO draft guidelines on dietary saturated and trans fatty acids: time for a new approach? BMJ. 2019 Jul 3;366:l4137. doi: 10.1136/bmj.l4137.
- Fattore E, Massa E. Dietary fats and cardiovascular health: a summary of the scientific evidence and current debate. Int J Food Sci Nutr. 2018 Dec;69(8):916-927. doi: 10.1080/09637486.2018.1455813. Epub 2018 Apr 4. Review.
- Mozaffarian D, Micha R, Wallace S. Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of randomized controlled trials. PLoS Medicine 2010;7:e1000252. doi: 10.1371/journal.pmed.1000252
- Truswell AS. Review of dietary intervention studies: effect on coronary events and on total mortality. Australian and New Zealand Journal of Medicine 1994;24:98-106.