HealthCert Blog

[Nutrition Research Review] Association between dietary fat intake and mortality from all-causes, cardiovascular disease, and cancer: A systematic review and meta-analysis of prospective cohort studies.

Recent research in nutrition science is driving a reconsideration of the role dietary fats play in chronic disease risk and mortality.

Dietary advice regarding fat intake in relation to reducing chronic disease risk has evolved over time from recommending lower intakes of total fat to more targeted advice focusing on reducing saturated and trans fats intakes, as opposed to reducing total fat per se. Indeed, the most recent Australian Dietary Guidelines, from 2013, suggest reducing saturated fat and trans-fats intakes in particular [1] as there is strong evidence supporting the health benefits of polyunsaturated fat [2] and plant-based monounsaturated fat (e.g. as found in olive oil) [3]. However, recently, research has challenged the idea that saturated fat intake is associated with poorer health outcomes [4, 5].

The systematic review and meta-analysis by Kim and colleagues aimed to elucidate association with dietary fat intake (total, saturated, monounsaturated, polyunsaturated, and trans-fats) and mortality from cancer, CVD and all-causes [6].

Published studies up until February 2020 of prospective observational studies that included exposures of dietary fat and fatty acid intakes, had outcome measures of mortality from all causes, CVD or cancer and reported relative risks and confidence intervals (or the data enabling their calculations) were included [6]. Studies exclusively exploring omega-3 polyunsaturated fatty acids and all-cause mortality were excluded. Nineteen prospective cohort studies that included more than one million adult participants and 195,515 deaths were included in the meta-analysis. Median follow up was 13.2 years (6-32 years).

Findings included:

Total fat intake: A 5% increase in energy from total fat was associated with a 1% lower risk of all-cause mortality and no significant associations were found for either CVD or cancer mortality and total fat intake.

Saturated fat intake: The positive association between mortality from all causes and CVD and percentage of dietary energy from saturated fat was non-linear, with no excess risk found at intakes >11%. For cancer mortality risk, a linear, positive association was found with increasing saturated fat intake.

Monounsaturated fat intake: Increasing monounsaturated fat intake by 5 % was associated with a 2% lower risk of all-cause mortality and no significant association was found between intake of monounsaturated fats and CVD and cancer mortality.

Polyunsaturated fat intake: A 5% increase in polyunsaturated fat intake was associated with a 7% lower risk of all-cause mortality, a 5% lower risk of CVD mortality and 4 % lower risk of cancer mortality.

Trans-fat intake: Trans-fat intake was positively associated with all-cause and CVD mortality, with a 1% increase in intake being associated with a 6% higher risk for both outcome measures. No association was found linking trans fat intake and cancer mortality.

This review provides support for the association of saturated fat intake with higher risk of death.

However, the authors note that a limitation of this study is that it does not provide insight into whether specific dietary saturated fat sources or types of saturated fats modify this observed relationship. For example, previous studies have found that red meat and processed foods, which are common sources of dietary saturated fat, are associated with increased mortality risk [7] but dairy foods, which are also a dietary source of saturated fat, (primarily in the form of odd-chain saturated fats), have been associated with lower mortality risk [8].

The findings of this review for polyunsaturated fat and trans-fat intakes and mortality risk were in line with existing evidence. The weaker associations found for monounsaturated fat intake and mortality were noted to potentially be related to the fact that this study did not distinguish between plant and animal monounsaturated fat sources, which are known to have differential effects on health outcomes [9].

These findings support the current guidelines on dietary fats that recommend supporting your patients in lowering their intake of saturated and trans-fats to reduce their chronic disease risk and mortality.

See the full article here.

Anna Millichamp, APD, Bond University

Learn more in the online Professional Diploma of Medical Nutrition Management.

References

1. National Health and Medical Research Council, Australian Dietary Guidelines. 2013, National Health and Medical Research Council.: Canberra.
2. Wan, Y., et al., Fish, long chain omega-3 polyunsaturated fatty acids consumption, and risk of all-cause mortality: A systematic review and dose-response meta-analysis from 23 independent prospective cohort studies. Asia Pacific Journal of Clinical Nutrition, 2017. 26(5): p. 939-956.
3. Schwingshackl, L. and G. Hoffmann, Monounsaturated fatty acids, olive oil and health status: a systematic review and meta-analysis of cohort studies. Lipids in Health and Disease, 2014. 13(1): p. 154.
4. Chowdhury, R., et al., Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary Risk. Annals of Internal Medicine, 2014. 160(6): p. 398-406.
5. de Souza, R.J., et al., Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ : British Medical Journal, 2015. 351: p. h3978.
6. Kim, Y., Y. Je, and E.L. Giovannucci, Association between dietary fat intake and mortality from all-causes, cardiovascular disease, and cancer: A systematic review and meta-analysis of prospective cohort studies. Clinical Nutrition, 2021. 40(3): p. 1060-1070.
7. Larsson, S.C. and N. Orsini, Red Meat and Processed Meat Consumption and All-Cause Mortality: A Meta-Analysis. American Journal of Epidemiology, 2013. 179(3): p. 282-289.
8. Mazidi, M., et al., Consumption of dairy product and its association with total and cause specific mortality – A population-based cohort study and meta-analysis. Clinical Nutrition, 2019. 38(6): p. 2833-2845.
9. Zhuang, P., et al., Dietary Fats in Relation to Total and Cause-Specific Mortality in a Prospective Cohort of 521 120 Individuals With 16 Years of Follow-Up. Circulation Research, 2019. 124(5): p. 757-768.

Citation

Kim Y, Je Y, Giovannucci EL. Association between dietary fat intake and mortality from all-causes, cardiovascular disease, and cancer: A systematic review and meta-analysis of prospective cohort studies. Clin Nutr. 2021 Mar;40(3):1060-1070. doi: 10.1016/j.clnu.2020.07.007. Epub 2020 Jul 14. PMID: 32723506.

Read more recent research.