Butter is not back: Limiting saturated fat still best for heart health

People who replace saturated fat (mainly found in meats and dairy foods) in their diets with refined carbohydrates do not lower their risk of heart disease, according to a new study led by researchers at Harvard T.H. Chan School of Public Health. On the other hand, those who replace saturated fats with unsaturated fats (found in vegetable oils and nuts) or whole grains lower their heart disease risk.

Many people fall back on carbs, especially refined carbs like white bread, when they reduce saturated fat in their diets, said senior author Frank Hu, professor of nutrition and epidemiology. This may in part explain findings from a controversial 2014 paper that called into question recommendations for limiting saturated fat for heart health, and led to headlines promoting the return of butter.

“Our research does not exonerate saturated fat,” said Hu. “In terms of heart disease risk, saturated fat and refined carbohydrates appear to be similarly unhealthful.”

The study appears online September 28, 2015 in the Journal of the American College of Cardiology.

This is the first prospective analysis to directly compare saturated fat with other types of fats and different types of carbohydrates in relation to heart disease risk.

Hu and colleagues looked at diet and health information from participants in two long-running observation studies, the Nurses’ Health Study (84,628 women) and the Health Professionals Follow-up Study (42,908 men), who were free of diabetes, cardiovascular disease, and cancer at baseline. Diet was assessed by food frequency questionnaires every four years. During follow-up, the researchers documented 7,667 cases of coronary heart disease (CHD).

They estimated that replacing 5% of energy intake from saturated fats with equivalent energy intake from either polyunsaturated fats, monounsaturated fats, or carbohydrates from whole grains was associated with 25%, 15%, and 9% lower risk of CHD, respectively. On the other hand, swapping 5% of saturated fat calories for the same amount of refined carbohydrates and sugars did not change CHD risk.

“In other words, refined carbs and sugars don’t lower CHD risk any more than saturated fats lower CHD risk (which they don’t),” said Adela Hruby, co-first author along with Yanping Li, both researchers in the Department of Nutrition. “People who choose refined carbs and sugars instead of saturated fat, thinking they’re making a healthier choice, are not doing themselves any favors in terms of heart health.”

The study’s analyses took into account cardiovascular risk factors such as age, body mass index, smoking, and physical activity.

“Our findings suggest that the low-fat, high-carb trends of the 1980s and 1990s are not effective in reducing risk of CHD,” said Li. “Dietary recommendations to reduce saturated fats should specify their replacement with unsaturated fats or with healthy carbohydrates, such as whole grains.”

Other Harvard Chan School authors of the study included Sylvia Ley, Dong Wang, Stephanie Chiuve, Laura Sampson, Eric Rimm, and Walter Willett.

The study cohorts were supported by grants of UM1 CA186107, R01 HL034594, R01 HL35464, R01 HL60712 and UM1 CA167552 from the National Institutes of Health.

“Saturated fat as compared to unsaturated fats and sources of carbohydrates in relation to risk of coronary heart disease: A prospective cohort study,” Yanping Li, Adela Hruby, Adam M. Bernstein, Sylvia H. Ley, Dong D. Wang, Stephanie E. Chiuve, Laura Sampson, Kathryn M. Rexrode, Eric B. Rimm, Walter C. Willett, Frank B. Hu, Journal of the American College of Cardiology, online September 28, 2015, doi: 10.1016/j.jacc.2015.07.055

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3 thoughts on “Butter is not back: Limiting saturated fat still best for heart health”

  1. Open Heart
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    Home > Volume 1, Issue 1 > Article rss
    Open Heart 2014;1: doi:10.1136/openhrt-2013-000032
    The cardiometabolic consequences of replacing saturated fats with carbohydrates or Ω-6 polyunsaturated fats: Do the dietary guidelines have it wrong?
    James J DiNicolantonio
    + Author Affiliations

    Cardiovascular research scientist and doctor of pharmacy, Ithaca, New York, USA
    Correspondence to
    Dr James J DiNicolantonio; [email protected]
    A recent publication by Malhotra1 was refreshing, inspiring and hit on an important topic that has been heavily debated for over 50 years, that is, are saturated fats as bad as we have been led to believe?

    History of the low-fat ‘diet-heart’ hypothesis
    The vilification of saturated fat by Keys2 began two decades before the seven countries study, where Keys showed a curvilinear association between fat calories as a percentage of total calories and death from degenerative heart disease from six countries. However, he excluded data from 16 countries that did not fit his hypothesis. Indeed, data were available at the time from 22 countries, and when all countries were looked at the association was greatly diminished.3 Furthermore, no association existed between dietary fat and mortality from all causes of death.3 Thus, past data promoted by Keys showing that an increased percentage of fat calories consumed increases the risk of death are not valid (and certainly could never have proved causation). These data seemingly lead us down the wrong “dietary-road” for decades to follow, as pointed out by others.4 ,5

    The consequences of replacing saturated fats with carbohydrates
    The initial Dietary Goals for Americans, published in 1977, proposed increasing carbohydrates and decreasing saturated fat and cholesterol in the diet.6 ,7 This stemmed from the belief that since saturated fats increase total cholesterol (a flawed theory to begin with) they must increase the risk of heart disease. Moreover, it was believed that since fat is the most “calorie-dense” of the macronutrients, a reduction in its consumption would lead to a reduction in calories and a subsequent decrease in the incidence of obesity, as well as diabetes and the metabolic syndrome. However, the advice to increase carbohydrate intake seemingly made things worse, with an increase in its consumption (mainly corn syrup) paralleling the increased incidence of diabetes and obesity in the USA.8 In this analysis, fat was not associated with type 2 diabetes when total energy intake was accounted for,8 and the intake of saturated fat in the USA during this time was also not on the rise.9 These data provide a strong argument that the increase in the consumption of refined carbohydrates was the causative dietary factor for the diabetes and obesity epidemic in the USA.

    These data are further strengthened by a randomised, controlled, dietary intervention trial comparing a low-fat (<10% saturated fat) versus a low-carbohydrate (12% of total calories from carbohydrates) diet.10 ,11 While both diets were low in calories (1500 kcal/day), the low-carbohydrate diet showed greater improvements on numerous endpoints such as (1) body fatness (abdominal fat, body mass), (2) lipids (triglycerides, apolipoprotein B (ApoB)), (3) glucose tolerance (glucose, insulin and insulin resistance—measured via homoeostasis model assessment), (4) inflammation (tumour necrosis factor α, interleukin (IL) 6, IL-8, monocyte chemotactic protein 1, E-selectin, intercellular adhesion molecule 1) and (5) thrombogenic markers (plasminogen activator inhibitor 1).10 ,11 Additionally, the low-carbohydrate diet provided (1) an increase in high-density lipoprotein cholesterol (HDL-C), (2) a reduction in the ApoB/ApoA-1 ratio and (3) a reduction in small, dense low-density lipoprotein (sdLDL), whereas all of these parameters were worsened on a low-fat diet.10 ,11 Thus, overall cardiometabolic health seems to improve to a greater extent when carbohydrate is restricted rather than fat.

    The assumption that a low-fat diet reduces the ‘bad’ cholesterol (ie, LDL) is an imprecise notion. While total LDL may be lowered with a reduced intake of dietary fat, if replaced with carbohydrate, this may increase sdLDL particles (ie, pattern B),10 ,11 which are more atherogenic than large buoyant LDL particles (ie, pattern A).12 Additionally, data indicate that a high saturated fat intake lowers sdLDL particles and raises large buoyant LDL particles.13 Thus, replacing carbohydrate with fat may improve the LDL particle size distribution (eg, pattern B shifted to pattern A). Lastly, if fat is replaced with carbohydrate, this may worsen the overall lipid profile (decrease in HDL-C, increase in triglycerides and increase in sdLDL particles).10 ,11

    Several other randomised trials indicate that a low-carbohydrate diet reduces weight and improves lipids more than a low-fat diet.14–18 Thus, reducing carbohydrates, as opposed to fat, seems to have more favourable effects on atherogenic dyslipidaemia, inflammation, thrombogenic and atherosclerotic surrogate markers.10–18 From these data, it is easy to comprehend that the global epidemic of atherosclerosis, heart disease, diabetes, obesity and the metabolic syndrome is being driven by a diet high in carbohydrate/sugar as opposed to fat, a revelation that we are just starting to accept.

    The consequences of replacing saturated fats with polyunsaturated (Ω-6) fats
    Not only has the condemnation of saturated fats led to an increased consumption of carbohydrates, it has also led to several dietary guidelines recommending replacement of saturated fats with polyunsaturated fats, without specifying which polyunsaturated fatty acid (ie, Ω-3 vs Ω-6). The recommendation for increasing polyunsaturated fat stems from pooled analyses of data looking at increasing Ω-3 and Ω-6 polyunsaturated fatty acids.19 ,20 However, a meta-analysis of randomised controlled trials showed that replacing a combination of trans-fats and saturated fats with Ω-6 polyunsaturated fats (without simultaneously increasing Ω-3 fatty acids) leads to an increased risk of death.21 These results were corroborated when data were recovered from the Sydney Diet Heart Study and included in an updated meta-analysis.22

    Other human trials, not included in the aforementioned meta-analysis, include the Anti-Coronary Club trial, which showed that more people died (overall (26 vs 6) and due to coronary heart disease (8 vs 0)) when saturated fat was replaced with polyunsatured fat.23 The National Diet Heart Trial, a randomised, double-blind study, also showed a higher number of cardiovascular events (n=4) on a diet that was high in the polyunsaturated(P)/saturated(S) fat ratio (2 : 1), than on a diet high in saturated fat (n=1, P/S=0.4).24 Thus, advice to replace saturated fats with polyunsaturated fats (ie, Ω-6) may increase the risk of coronary heart disease, cardiovascular events, death due to coronary heart disease and overall mortality.21–24

    Reasons for the potential harmful effects of Ω-6 fatty acids may be due to their promotion of cancer, suppression of the immune system, lowering of HDL-C and increasing the susceptibility of LDL to oxidation.25 Further evidence indicates a role of Ω-6 in promoting prostate26–28 and breast cancer.29 This is supported by the Anti-Coronary Club study, where there was 71% increased risk of death from causes other than coronary heart disease among individuals who were placed on a diet designed to increase the P/S ratio in those who had not experienced a new coronary event.30 Moreover, in a controlled clinical trial by Dayton et al,31 there was a greater than threefold increased risk of death due to carcinoma when saturated fat (mainly of animal origin) was substituted for Ω-6 polyunsaturated fat (including corn, soybean, safflower and cottonseed). The potential harms of replacing saturated fat with carbohydrates or Ω-6 polyunsaturated fats are summarised in box 1.

    Box 1
    The potential harms of replacing saturated fat with carbohydrates or Ω-6 polyunsaturated fats
    The potential harms of replacing saturated fat with carbohydrates

    Increase in small, dense LDL particles.

    Shift to an overall atherogenic lipid profile (lower HDL-C, increase in triglycerides and an increase in the ApoB/ApoA-1 ratio).

    Smaller improvements in glucose tolerance, body fatness, weight, inflammation and thrombogenic markers.

    Increased incidence of diabetes and obesity.

    The potential harms of replacing saturated fat with omega-6 polyunsaturated fats

    Increased risk of cancer.

    Increased risk of coronary heart disease, cardiovascular events, death due to heart disease and overall mortality.

    Increased oxidised LDL-C.

    Reduction in HDL-C.

    Lack of evidence for a low-fat diet
    Data are lacking in the support of a low-fat diet. In the low-fat diet in myocardial infarction trial, a controlled trial was performed to test if a low-fat diet would improve outcomes in 264 men who had recently recovered from a first myocardial infarction.32 Despite the fact that patients in the low-fat diet group ate significantly less fat (45 g/day vs 110–130 g/day), consumed less calories (approximately 1950 calories vs 2450 calories), obtained a lower cholesterol level and achieved a greater fall in body weight than those in the control group, there was no difference in definite reinfarction or death.

    In the Women's Health Initiative (WHI), a randomised controlled trial including 48 835 postmenopausal women, a low-fat diet was not shown to reduce coronary heart disease, stroke or cardiovascular disease,33 despite a significant reduction in LDL-C, nor was there a reduction in cancer.34 ,35 A meta-analysis by Siri-tarino et al36 consisting of 21 prospective epidemiological studies, derived from 347 747 participants, indicated that the intake of saturated fat does not increase coronary heart disease or cardiovascular disease. Moreover, a recent Cochrane meta-analysis indicated that changing dietary fat intake does not affect total mortality or cardiovascular mortality.37 Although reducing saturated fat was associated with a reduced risk of cardiovascular events by 14%, this was not shown with reducing total fat consumption.37 While the WHI study and the Siri-tarino and Cochrane meta-analyses cannot be taken at face value, taken together with “the low-fat diet in myocardial infarction trial”, a compelling argument can be made for the general lack of evidence in support of a low-fat diet. Dietary recommendations based on evidence from the literature are summarised in box 2.

    Box 2
    Dietary recommendations based on evidence from the literature
    Dietary guideline recommendations suggesting the replacement of saturated fat with carbohydrates/Ω-6 polyunsaturated fats do not reflect the current evidence in the literature.

    A change in these recommendations is drastically needed as public health could be at risk.

    The increase in the prevalence of diabetes and obesity in the USA occurred with an increase in the consumption of carbohydrate not saturated fat.

    There is no conclusive proof that a low-fat diet has any positive effects on health. Indeed, the literature indicates a general lack of any effect (good or bad) from a reduction in fat intake.

    The public fear that saturated fat raises cholesterol is completely unfounded as the low-density lipoprotein particle size distribution is worsened when fat is replaced with carbohydrate.

    A public health campaign is drastically needed to educate on the harms of a diet high in carbohydrate/sugar.

    It would be naive to assume that any recommendations related to carbohydrate or fat intake would apply to processed foods, which undoubtedly should be avoided if possible.

  2. What an utterly ridiculous claim,assuming that participants’ food logs were entirely accurate. In reality, participants could just as easily not replaced 5% of their saturated fat
    – but done entirely the reverse.

    Furthermore, with hydrogenated fats still present in many food products, their known tendency to cause heart disease would have severely skewed the results as different people will have eaten more or less trans fat.

    What an utter fail. This is a last ditch attempt by the margarine industry to demonise saturated fat which DOESN’T cause heart disease. Margarine is a slew of nasty chemicals and is GREY in colour prior to being dyed yellow. Furthermore, it’s only one molecule away from plastic.

    For proper reliable studies into heart disease, look for some studies, for example…

    ‘An international research collaboration led by the University of Cambridge analysed existing cohort studies and randomised trials on coronary risk and fatty acid intake. They showed that current evidence does not support guidelines which restrict the consumption of saturated fats in order to prevent heart disease. The researchers also found insufficient support for guidelines which advocate the high consumption of polyunsaturated fats (such as omega 3 and omega 6) to reduce the risk of coronary disease. – See more at: http://www.cam.ac.uk/research/news/new-evidence-raises-questions-about-the-link-between-fatty-acids-and-heart-disease#sthash.Dpz2eOLq.dpuf.’…

    and yet another major study (http://openheart.bmj.com/content/2/1/e000196.full) concludes the same outcome.

    This is the truth.

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