Major Study Exonerates Saturated Fat
Big review sees no heart risk from saturated fat, but harm from omega-6-rich vegetable oils
Big review sees no heart risk from saturated fat, but harm from omega-6-rich vegetable oils
A large study released earlier this week should mark a turning point in public health policy.
Since the early 1970's official health authorities have asserted that the saturated fat in meat, butter and cheese causes heart disease.
But, combined with other recent research, the findings of this major evidence review further discredit that claim.
Doubts about the demonization of saturated fat have simmered for decades, ever since it became clear that conventional wisdom rested on a shaky, fraudulent foundation.
And it's rarely noted that there are many kinds of saturated fat, some of which don't negatively affect blood cholesterol profiles (e.g., stearic acid, which predominates in beef and chocolate).
Since the new study focused on saturated animal fats, some of which are blamed for heart disease, we'll be referring to those when we use the term “saturated fat” in this article.
Drumbeat of doubt preceded the new study
As we reported last year – see “Heart-Diet Myths Get a Busting” – a British cardiologist's bold essay rebutting conventional wisdom on saturated fat made big waves in the medical community.
In an editorial in the British Medical Journal, Aseem Malhotra, M.D., noted that the demonization of saturated fat flowed largely from the famed Seven Countries Study … whose authors cherry-picked the evidence.
In fact, some of countries they studied had high saturated fat intakes but low rates of heart disease … a fact they hid by leaving those out of their analysis.
The authors of the Seven Countries Study actually collected diet and health data from 22 countries, but ignored inconvenient data from 16 … and subsequent analyses of the data collected from all 22 nations disproved their theory.
Growing doubts were fueled by a Harvard-led 2010 study that found “no significant evidence … that dietary saturated fat is associated with an increased risk of cardiovascular disease [CVD].” (Siri-Tarino PW et al. Am J Clin Nutr. 2010 Mar;91(3):502-9)
As the same scientists wrote in a second study, “More data are needed to elucidate whether CVD risks are likely to be influenced by the specific nutrients used to replace saturated fat.” (Siri-Tarino PW et al. Am J Clin Nutr. 2010 Mar;91(3):535-46)
They were referring to growing evidence that official urgings to replace saturated fats with polyunsaturated vegetable oils caused Americans to consume omega-6 fats in extreme excess.
In turn, excessive intake of omega-6 fats yields the kind of chronic, “silent” inflammation that drives heart disease, dementia, and more.
Doubts raised by those and other studies were echoed in a 2011 lecture by prominent heart researcher Dr. Rozenn Lemaitre (see “Saturated Fat Seen as Heart Red Herring”).
And as she said, the evidence linking saturated fat and risk of cardiovascular disease is “not conclusive”, and must be considered in the context of its replacement by refined carbohydrates (sugar and white flour) and omega-6-rich vegetable oils (corn, soy, safflower, sunflower, and cottonseed).
Earlier this year, cardiovascular researcher James DiNicolantonio, PharmD, wrote an editorial in the journal Open Heart questioned official diet guidelines, calling the benefits of a low-fat diet -- especially one that replaces saturated fats with carbohydrates or omega-6-rich vegetable oils – “severely challenged”.
As he said, previous evidence reviews “inappropriately combined trials that were mixed omega-3 and omega-6 and stated that they were omega-6 trials.
When looking at the trials that solely replaced saturated fat with omega-6 [fats], there was an increase in CHD [coronary heart disease] and CV [cardiovascular] death.”
Major evidence review finds no link between saturated fat and heart disease
The authors of the new evidence review examined clinical and population studies that involved 659,304 people from 18 countries, all published before July 1, 2013:
- 32 population studies (530,525 participants) comparing dietary intake of fatty acids to rates of heart disease.
- 17 population studies (25,721 participants) comparing people's fatty acid blood levels to rates of heart disease.
- 27 randomized, controlled clinical trials (103,052 participants) that tested the effects of fatty acid supplements (including omega-3 fish oil and omega-6 vegetable oils) on heart disease risk.
After analyzing the data, they concluded that people who ate lots of saturated fat do not experience more heart disease than those who ate less.
As they wrote, their analysis “… did not yield clearly supportive evidence for current cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of saturated fats.” (Chowdhury R et al. 2014)
Nor did they find less heart disease in people who consume lots of monounsaturated fat (e.g., olive oil and avocado) or polyunsaturated fat from vegetable oils like corn, soy, safflower, sunflower, and cottonseed.
Often, when people cut back on fats they eat more refined carbohydrates, which raise blood levels of the kinds of fats proven worst for cardiovascular health: namely, triglycerides and dense, small-particle LDL cholesterol.
By contrast, saturated fat primarily raises levels of large, “fluffy” LDL cholesterol, which doesn't appear to harm cardiovascular health.
And although it is not widely known, saturated fat tends to raise levels of “good” HDL cholesterol.
Most expert commenters agreed that instead of consuming lots of vegetable oil, people should focus on foods typical of the Mediterranean diet: fish, nuts, beans, high-fiber grains, fresh cheeses, and extra virgin olive oil (see “Extra Virgin Olive Oil Confirmed as Best Cardiac Prevention Choice”).
A large clinical trial published last year – which was not covered by the new evidence review – found that a Mediterranean diet with added nuts and extra virgin olive oil reduced heart attacks and strokes, compared with a lower-fat diet with more starches (see “Mediterranean Diet Cut Heart Deaths by 30%”).
Omega-3s not found to reduce heart risk
Oddly, the evidence review did not conclude that omega-3 fish oil reduces the risk of heart disease attacks significantly.
But, as Harvard researchers noted two years ago, most of the extant trials have involved people already diagnosed with and being treated for cardiovascular disease, thus putting omega-3s to a very tough, unfair test (Hu FB, Manson JE 2012).
And very few trials have taken into account the amounts of competing omega-6 fats the participants were consuming.
When that's been done, it's been found that the high omega-6 intake typical of modern diets blunts the heart benefits of omega-3s.
In total, the body of evidence affirming omega-3s' role in optimizing heart health and reducing heart risks approaches overwhelming status.
Most recently, we reported on a well-designed study that persuasively links Japan's very low rate of heart disease to the nation's fish-heavy diet … see “Do Fishy Diets Drive Japan's Superior Heart Health?”.
The best evidence comes from several large, well-designed clinical trials, supported by dozens of epidemiological studies (see “Does Fish Oil Really Help Hearts?”).
And a generally positive view of omega-3s was affirmed by an earlier evidence review (Marik PE, Varon J et al. 2009) … see “Omega-3s Cut Heart Risks & Death Rates in Clinical Trial.”
The same Harvard duo summarized the evidence last year (Hu FB, Manson JE 2012):
“Omega-3 fatty acids are among the most extensively studied nutrients for their potential cardiovascular benefits.”
“A large body of evidence from experimental, clinical, and epidemiologic research has demonstrated the potential benefits of EPA-rich and DHA-rich fish oil on cardiovascular health.”
- “Consistent findings from prospective observational cohort investigations indicate that regular consumption of fatty fish (two times per week) is associated with a significantly lower risk of cardiovascular death.”
This record explains why the American Heart Association and public health authorities worldwide recommend eating fatty fish and/or taking fish oil supplements on a routine basis.
We'd add these reasons for believing that omega-3s aid heart health:
- They exert a moderating influence on chronic inflammation … a proven promoter of cardiovascular disease.
- Thousands of cell, animal, and clinical studies detail the biological effects of long-chain omega-3s (EPA and DHA) ... almost all considered good for heart health.
- Clinical trials generally find that omega-3 fish oil supplements produce beneficial vascular, lipid-profile, heart-rhythm, and inflammation-damping effects.
- Most reviews of controlled trials conclude that fish-rich diets or omega-3 fish oil reduce the risk of heart-related deaths and/or adverse cardiac events (Wang C et al. 2006; León H et al. 2008; Marik PE et al. 2009).
- Several large clinical trials found that omega-3 fish oil reduced the risk of sudden cardiac death, which makes up half of all heart-related deaths.
Last, but not least, diets rich in seafood source omega-3s appear to extend people's lifespans as well as their “health spans” … see “High Omega-3 Levels Boost Longevity> /shop/pc/articlesView.asp?id=2013<”.
Chowdhury R et al. Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary Risk: A Systematic Review and Meta-analysis. Ann Intern Med. 2014;160(6):398-406-406. doi:10.7326/M13-1788
Estruch R, Ros E, Salas-Salvadó J, Covas MI, D Pharm, Corella D, Arós F, Gómez-Gracia E, Ruiz-Gutiérrez V, Fiol M, Lapetra J, Lamuela-Raventos RM, Serra-Majem L, Pintó X, Basora J, Muñoz MA, Sorlí JV, Martínez JA, Martínez-González MA; the PREDIMED Study Investigators. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet. N Engl J Med. 2013 Feb 25. [Epub ahead of print]
Hadziabdić MO, Bozikov V, Pavić E, Romić Z. The antioxidative protecting role of the Mediterranean diet. Coll Antropol. 2012 Dec;36(4):1427-34. Serra-Majem L, Roman B, Estruch R. Scientific evidence of interventions using the Mediterranean diet: a systematic review. Nutr Rev. 2006 Feb;64(2 Pt 2):S27-47. Review.