New Study – More Animal Fat Consumption less cardiovascular disease

INTRODUCTION: A brand new study published last week in Nutrients looked at health and nutrition data from 158 countries worldwide and found that total fat and animal fat consumption were least associated with the risk of cardiovascular disease. As well, the study found that high carbohydrate consumption, particularly as cereals and wheat was most associated with the risk of cardiovascular disease. Significantly, both of these relationships held up regardless of a nation’s average national income.

Data from this study adds to the mounting evidence from 8 recent meta-analyses and systemic reviews of randomized control trials (RCT) summarized in this article that did not find an association between  saturated fat intake and the risk of heart disease[1-8]. It also supports evidence from the recent global PURE (Prospective Urban and Rural Epidemiological) study published in The Lancet this past December which found that those who ate the largest amounts of saturated fats had significantly reduced death rates, and that those that ate the lowest amounts of saturated fat (6-7% of calories) had increased risk of stroke [9].

Global Correlates of Cardiovascular Risk: a comparison of 158 Countries

This new study compared the average intake of 60 food items with obesity rates and life expectancy in 158 countries and found that a relationship existed between eating specific foods and raised blood pressuredeath from cardiovascular disease and raised blood glucose (high blood sugar) — all of which are associated with cardiovascular disease.  The study examined nutritional data from  1993-2011 and found that total fat consumption and animal fat consumption were the dietary factors least associated with the risk of cardiovascular disease and that high carbohydrate consumption, especially as cereals and wheat was the dietary factor most associated with the risk of cardiovascular disease [10].

These findings add to the mounting evidence which calls into question whether dietary saturated fat is related to heart disease.

Total Cholesterol and Cardiovascular Risk

The present study found that eating animal fat and animal protein raised total cholesterol, however total fat and animal protein consumption were found to have a very impressive negative relationship with cardiovascular death in the European data, and a moderately negative relationship to cardiovascular death, worldwide. That is, the more total fat and animal protein eaten, the lower cardiovascular death rates were.

Often in studies,  the assumption is that high LDL is linked to risk of cardiovascular disease – not that there is a direct relationship between animal / saturated fat and cardiovascular disease.  That is, high LDL is a surrogate marker of cardiovascular disease. But does that assumption hold weight?

Perhaps a better question is “which LDL“? Small, dense LDL cholesterol  which easily penetrates the artery wall is associated with heart disease [11,12,13,14], but the large, fluffy LDL cholesterol is not [15,16], so studies seeking to impute LDL as the cause of cardiovascular diseasee need to differentiate between these LDL particles.

As well, total cholesterol is made up of the different sub-particles of LDL cholesterol, HDL cholesterol, VLDL cholesterol and triglycerides (TG), so lumping them all in together as ‘total cholesterol‘ doesn’t tell us anything about risk of cardiovascular disease. We know that dietary saturated fat consistently raises the “good” HDL-cholesterol — which moves cholesterol away from the arteries and back to the liver where it can either be re-used or eliminated [17,18], so higher saturated fat intake will raise “good” HDL cholesterol, which in turn will raise total cholesterol. Total cholesterol going up is not a ‘bad’ thing.

What is important is not that total cholesterol went up but that along with increased total cholesterol, cardiovascular disease went down.
Higher Blood Sugar Associated with Higher Consumption of Cereals and Wheat

One finding of this study was that higher blood sugar (a known risk factor for cardiovascular disease) was most strongly associated with indicators of obesity such as high body mass index (BMI). What was new however is that higher consumption of cereals, especially cereals and wheat was associated with higher cardiovascular disease.

Researchers remarked that such results were not surprising “because the links between raised blood glucose, obesity, type 2 diabetes and cardiovascular disease are well established [19]”.

“…regardless of the statistical method used, the results always show very similar trends and identify high carbohydrate consumption (mainly in the form of cereals and wheat, in particular) as the dietary factor most consistently associated with the risk of CVDs.

High carbohydrate consumption, particularly as cereals and wheat was the dietary factor most consistently associated with the risk of cardiovascular disease.

Researchers looked at a maximum number of potentially significant variables and compared them to results across different regions and time periods and while they acknowledged that the accuracy of the data from developing countries may be lower, the global results that they found confirmed their earlier 2016 study data from European data only which found a significant link between cardiovascular disease and high carbohydrate consumption [20].

Of significance, the above associations held up regardless of a nation’s average national income.

Given these finding support those of the PURE epidemiological study [9] would lend support the notion that one can compare data between countries of substantially different level of income (as the PURE study did) and that high-carbohydrate and low-fat diets are not necessarily associated with poverty, as claimed [21].

The PURE study findings and those of this present study challenge the very basis of the long-standing ‘diet-heart hypothesis‘ and it certainly results in some uncertainty as to what constitutes a healthy diet.

In my view, what is needed are some well-designed randomized controlled trials to determine if saturated fat intake is directly associated with cardiovascular disease – and not associated with a surrogate marker, such as LDL cholesterol.

Purported Weakness of the Data

Self-reported food-frequency questionnaires on which this study is based have long been criticized as being unreliable, however it is important to note that in the United States the NHANES Dietary Data and the Continuing Survey of Food Intakes by Individuals (USA) has also collected data using food-frequency questionnaires and such data is used as the “cornerstone to inform nutrition and health policy” [22].

In Canada, the Canadian Community Health Survey (CCHS) relies on a 24-hour recall data which is known to researchers to result in under-reporting of food intake, especially among those with a high BMI and with adolescents [23].  Given that the 2017 Obesity Update found Canada among its most overweight countries — with 25.8% of the population aged 15 and over considered obese [24], the CCHS data becomes less and less reliable, as obesity rates continue to climb.

Enduring Belief – despite recent evidence

The results of this most recently published study embody the same findings as the recent global PURE (Prospective Urban and Rural Epidemiological) study [9] publish this past December in The Lancet which found a link between raised cholesterol and lower cardiovascular risk.

This study also confirms the findings of the eight recent meta-analysis and systemic reviews of randomized control trials (RCT) summarized in the previous article which did not find an association between saturated fat intake and the risk of heart disease [1-8].

Yet, in spite of recent robust evidence there is an enduring belief that ‘saturated fat causes heart disease’ — a belief which has influenced nutrition guidelines in both the US and Canada for 40 years (since 1977).

As elaborated on in a recent article, it is now known that the ‘diet-heart hypothesis‘ originated by Ancel Keys and supposedly confirmed in his ‘Seven Countries Study’ omitted known data from 22 available countries  and that when all countries were factored in there was a great deal more scatter showing a much weaker relationship between dietary fat and death by coronary heart disease than was suggested by Keys’s data.

Also as covered previously, it has been known since December 2016 that the three Harvard researchers who vindicated sugar as the cause of heart disease and blamed dietary fat — were funded by the sugar industry and that one one of those 3 researchers, Dr. DM Hegsted contributed to and edited the 1977 US Dietary Guidelines which embodied his findings of 10 years earlier, advising Americans to reduce their intake of saturated fat and cholesterol in order to reduce their risk of heart disease.

Also covered in a previous article, Canadian Dietary Recommendations regarding dietary intake of saturated fat were based on ‘health claim assessments’ conducted by Health Canada in 2000 (18 years ago) titled Dietary Fat, Saturated Fat, Cholesterol, Trans Fats and Coronary Heart Disease which was based on the US literature available from 1993-2000 and which concluded that a health risk exists between saturated fat and heart disease.

Given all of the factors mentioned above, it is my conviction that before the American and Canadian governments revise their respective national Dietary Guidelines what is needed is for them to conduct a long-overdue external, independent scientific review of the current evidence for the enduring belief that saturated fat contributes to heart disease.

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To our good health,

Joy

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References

  1. Skeaff CM, PhD, Professor, Dept. of Human Nutrition, the University of Otago, Miller J. Dietary Fat and Coronary Heart Disease: Summary of Evidence From Prospective Cohort and Randomised Controlled Trials, Annals of Nutrition and Metabolism, 2009;55(1-3):173-201
  2. Hooper L, Summerbell CD, Thompson R, Reduced or modified dietary fat for preventing cardiovascular disease, 2012 Cochrane Database Syst Rev. 2012 May 16;(5)
  3. Chowdhury R, Warnakula S, Kunutsor S et al, Association of Dietary, Circulating, and Supplement Fatty Acids with Coronary Risk: A Systematic Review and Meta-analysis, Ann Intern Med. 2014 Mar 18;160(6):398-406
  4. Schwingshackl L, Hoffmann G Dietary fatty acids in the secondary prevention of coronary heart disease: a systematic review, meta-analysis and meta-regression BMJ Open 2014;4
  5. Hooper L, Martin N, Abdelhamid A et al, Reduction in saturated fat intake for cardiovascular disease, Cochrane Database Syst Rev. 2015 Jun 10;(6)
  6. Harcombe Z, Baker JS, Davies B, Evidence from prospective cohort studies does not support current dietary fat guidelines: a systematic review and meta-analysis, Br J Sports Med. 2017 Dec;51(24):1743-1749
  7. Ramsden CE, Zamora D, Majchrzak-Hong S, et al, Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73), BMJ 2016; 353
  8. Hamley S, The effect of replacing saturated fat with mostly n-6 polyunsaturated fat on coronary heart disease: a meta-analysis of randomised controlled trials, Nutrition Journal 2017 16:30
  9. Dehghan M, Mente A, Zhang X et al, The PURE Study – Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study. Lancet. 2017 Nov 4;390(10107):2050-2062
  10. Grasgruber P, Cacek J, Hrazdira E, et al, Global Correlates of Cardiovascular Risk: A Comparison of 158 Countries, Nutrients 201810(4), 411.
  11. Tribble DL, Holl LG, Wood PD, et al. Variations in oxidative susceptibility among six low density lipoprotein subfractions of differing density and particle size. Atherosclerosis 1992;93:189–99
  12. Gardner CD, Fortmann SP, Krauss RM, Association of Small Low-Density Lipoprotein Particles With the Incidence of Coronary Artery Disease in Men and Women, JAMA. 1996;276(11):875-881
  13. Lamarche B, Tchernof A, Moorjani S, et al, Small, Dense Low-Density Lipoprotein Particles as a Predictor of the Risk of Ischemic Heart Disease in Men, 
  14. Packard C, Caslake M, Shepherd J. The role of small, dense low density lipoprotein (LDL): a new look, Int J of Cardiology,  Volume 74, Supplement 1, 30 June 2000, Pages S17-S22
  15. Genest JJ, Blijlevens E, McNamara JR, Low density lipoprotein particle size and coronary artery disease, Arteriosclerosis, Thrombosis, and Vascular Biology. 1992;12:187-195
  16. Siri-Tarino PW, Sun Q, Hu FB, Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease, The American Journal of Clinical Nutrition, Volume 91, Issue 3, 1 March 2010, Pages 502–509
  17. Mensink RP, Zock PL, Kester A, Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials, The American Journal of Clinical Nutrition, Volume 77, Issue 5, 1 May 2003, Pages 1146–1155
  18. Toth PP, The “Good Cholesterol” – High Density Lipoprotein, Circulation 2005;111:e89-e91
  19. Després, J.P.; Lemieux, I.; Alméras, N. Abdominal obesity and the metabolic syndrome. In Overweight and the Metabolic Syndrome; Springer: New York, NY, USA, 2006; pp. 137–152
  20. Grasgruber, P.; Sebera, M.; Hrazdira, E.; Hrebickova, S.; Cacek, J. Food consumption and the actual statistics of cardiovascular diseases: An epidemiological comparison of 42 European countries. Food Nutr. Res. 201660, 31694.
  21. Sigurdsson, AF, The Fate of the PURE Study – Fat and Carbohydrate Intake Revisited, Doc’s Opinion, October 16 2017,  www.docsopinion.com/2017/10/16/pure-study-fats-carbohydrates/
  22. Ahluwalia N, Dwyer J, Terry A, et al; Update on NHANES Dietary Data: Focus on Collection, Release, Analytical Considerations and Uses to Inform Public Policy, Advances in Nutrition, Volume 7, Issue 1, 1 January 2016, Pages 121–134
  23. Health Canada, Reference Guide to Understanding and Using the Data – 2015 Canadian Community Health Survey – Nutrition, June 2017
  24. OECD Health Statistics 2017, June 2017, http://www.oecd.org/els/health-systems/Obesity-Update-2017.pdf

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Author: Joy Kiddie, MSc, RD

Joy Y Kiddie MSc., RD - I'm a Registered Dietitian in private practice in British Columbia, Canada that provides low carb and ketogenic services in-person in my Coquitlam office, as well as by Distance Consultation (using Skype / telephone).