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EVIDENCE-BASED MEDICINE: SUMMARY OF STUDY
Year : 2017  |  Volume : 15  |  Issue : 4  |  Page : 288-289

Are saturated fats in the diet bad for the heart? – A summary of the prospective urban rural epidemiology study


Christian Medical College, Vellore, India

Date of Web Publication17-Nov-2017

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/cmi.cmi_79_17

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How to cite this article:
Thomas TA. Are saturated fats in the diet bad for the heart? – A summary of the prospective urban rural epidemiology study. Curr Med Issues 2017;15:288-9

How to cite this URL:
Thomas TA. Are saturated fats in the diet bad for the heart? – A summary of the prospective urban rural epidemiology study. Curr Med Issues [serial online] 2017 [cited 2020 Jun 1];15:288-9. Available from: http://www.cmijournal.org/text.asp?2017/15/4/288/218646

Source: This is a summary of the study: Prospective Urban Rural Epidemiology (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.[1] Summary prepared by Dr. Tony Abraham Thomas, Christian Medical College, Vellore, India.

Clinical Question: Are dietary fats, especially saturated fats such as butter, bad for the heart? Does high carbohydrate consumption affect health when compared to fats?

Authors' conclusions: (1) High intake of carbohydrates (>60% of energy) was associated with higher risk of mortality, while high consumption of fats and proteins was associated with a lower risk of total mortality and noncardiovascular disease mortality. (2) Total fat consumption and individual types of fats were not associated with cardiovascular disease or cardiovascular events such as myocardial infarction and death. (3) Saturated fat intake has an inverse association with risk of stroke.


  Why this Study? Top


Diet is one of the modifiable risk factors in cardiovascular disease, and dietary fat has often been painted as the villain in diet, considered harmful to the health of the heart. A series of studies in the early 60s and 70s appearing to support this premise and dietary advice has often encouraged a diet with reduced fat content. As a result, many food products have been considered “heart healthy” because they contained less fats, irrespective of the amount of processed sugars within these products. The role of the sugar industry and the financial implications of promoting sugar as being harmless when compared to fats have also been implicated in promoting this idea. However, the association between diet and cardiovascular disease, especially the adverse role of saturated fats, has been the focus of tremendous controversy in the recent years, with several studies and editorials questioning the widely accepted role of fats.[2],[3] Many researchers have questioned the negative image of fats, stating that the evidence underlying the premise was often misinterpreted and was based on observational studies without considering several studies that did not support this.[2],[4] Moreover, most studies in the past were based on populations in North America and Europe, where the consumption of animal-based saturated fats was very high. Hence, are fats really as harmful to cardiovascular health as believed and is this applicable to all individuals across geographical boundaries? The Prospective Urban Rural Epidemiology (PURE) study is an attempt to answer this question. This is a prospective epidemiological cohort study involving 200 investigators who collected data on more than 135,000 individuals from 18 countries across five continents, with a median follow-up of 7.4 years.




  Results Top


  • A total of 135,335 individuals aged 35–70 years were recruited and followed up, and there were 5796 deaths and 4784 major cardiovascular disease events
  • Dietary variations – Carbohydrate intake was higher in China, South Asia, and Africa compared with other regions. In South Asia, about 65% of the population consume at least 60% of energy from carbohydrate and 33% consume at least 70% of energy from carbohydrate. The highest amount of fat consumed was in North America, Europe, Middle East, and Southeast Asia. Intake of protein was highest in South America and Southeast Asia
  • Higher carbohydrate intake (>60% of energy) was associated with an increased risk of total mortality (95% confidence interval [CI]: 1.12–1.46, P = 0.0001)
  • High intake of total fat and each type of fat (saturated, monounsaturated, and polyunsaturated fats) was associated with lower risk of total mortality (95% CI: 0.67–0.87, P < 0.0001) and was not associated with the risk of cardiovascular disease or major cardiovascular disease events such as myocardial infarction and death
  • Higher saturated fat intake was associated with lower risk of stroke (95% CI: 0.64–0.98, P = 0.0498).



  Discussion Top


Dietary advice by nutritionists and physicians has conventionally been to reduce the amount of total fat consumption (especially saturated fats such as butter) to reduce the levels of low-density lipoprotein-cholesterol. The evidence for this has been weak and was historically based on studies focused on particular communities with a high intake of saturated fats. The initial findings of the PURE study have shown that a high intake of fats (of all types) is not associated with an increased risk of cardiovascular disease and is actually associated with a decreased risk of stroke and major cardiovascular events. An increased intake of carbohydrates, on the other hand, is associated with significant increase in mortality. This upends much of the dietary advice that has been in vogue in popular media as well as in medical practice. Saturated fats, typically those of animal origin (butter, ghee, etc.), may not be the “heart killers” that they were portrayed to be.

A carbohydrate-rich diet (>60% of energy provided) which is typical of Asian meals may not be the most healthful option and refined sugars (confectionaries, refined rice, and flour) contribute to much of the associated mortality. Many modern diets prescribed today (Mediterranean, Paleo) tend to have prominent protein/vegetable components with a minimal or negligible inclusion of dietary fats. The authors have commented that a balanced diet containing all components (carbohydrate, fats, proteins, fiber, and minerals), with no component being abandoned (unless there is a medical reason to do so), contributes to the overall health and fats, especially should not be excluded.

Strengths and limitations

The study population included a wide geographical distribution with people of different economic groups and is therefore more representative of the general global population than studies done earlier. The results of the study therefore can be applied to all population groups and are useful in dietary recommendations around the world. While the study does show that a high intake of fats is inversely associated with the risk of cardiovascular events and stroke, whether this is protective against these illnesses is something that cannot be commented from the results and will require further studies focused on this aspect. The methodology is robust and the follow-up also appears to be meticulous. The results will therefore be an important contributor to public health measures in the future.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Dehghan M, Mente A, Zhang X, Swaminathan S, Li W, Mohan V, et al. Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): A prospective cohort study. Lancet 2017. pii: S0140-6736(17)32252-3.  Back to cited text no. 1
    
2.
Sacks FM, Lichtenstein AH, Wu JH, Appel LJ, Creager MA, Kris-Etherton PM, et al. Dietary fats and cardiovascular disease: A Presidential Advisory from the American Heart Association. Circulation 2017;136:e1-23.  Back to cited text no. 2
    
3.
Nissen SE. U.S. dietary guidelines: An evidence-free zone. Ann Intern Med 2016;164:558-9.  Back to cited text no. 3
    
4.
Praagman J, Beulens JW, Alssema M, Zock PL, Wanders AJ, Sluijs I, et al. The association between dietary saturated fatty acids and ischemic heart disease depends on the type and source of fatty acid in the European Prospective Investigation into Cancer and Nutrition-Netherlands cohort. Am J Clin Nutr 2016;103:356-65.  Back to cited text no. 4
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