Post by Cliff Harvey
Due to the high-fat nature of a ketogenic or LCHF diet they have been considered to be potentially hazardous for those with cardiovascular disease (CVD).
Publicly available information (i.e. position statements and general patient information) from public health groups often include cautions against the use of VLCDs due to these perceived risks. Diabetes New Zealand states in their article on Low Carbohydrate Diets that “Eating more protein and fat may increase your risk of heart disease in the long term.” (1).
So are ketogenic diets dangerous for heart health?
LCHF and ketogenic diets and cardiovascular risk
Ketogenic diets are by nature high in fat and thus may also be high in saturated fat, although not necessarily so (for example if someone following a VLCD were prioritising PUFAs over SFAs). In their position statement on LCHF diets from 2014 Dietitians NZ states “Dietitians NZ considers there not to be any substantive evidence that saturated fat is good for you in the long term.” However in contrast to this blanket statement there is a lack of statistical evidence linking reduced fat or reduced saturated fat with cardiovascular disease end points and there is also limited trial data showing that a HIGH CARBOHYDRATE diet is good for you in the long term!
A Cochrane Review (2) of RCTs on the effects of modifying fat intake and reduced fat intakes found no overall effect of the diets on total mortality or cardiovascular disease mortality. Other meta-analyses also find little statistical evidence for an effect of modified saturated fat intake on CVD mortality (3; 4).
Links between saturated fat intake and CVD end points are primarily found when in modified fat diets, where saturated fat is replaced with another macronutrient, typically either carbohydrate or another fat class (PUFA or MUFA). For example Jakobsen et al. (5) demonstrated from cohort data a reduction in coronary disease events and coronary disease mortality when saturated fat was replaced by polyunsaturated fats.
However no association was noted when SFAs were replaced with either MUFAs or carbohydrate, suggesting a positive role in cardio-protection from PUFA intake, and not an absolute effect from the ingestion of SFAs, and casting doubt on the common recommendation to replace saturated fat with carbohydrate and/or MUFAs. More specifically it is suggested that omega 3 PUFAs may be cardio-protective and that this may account for the benefits seen with PUFA for SFA substitution. The meta-analysis by Skeaff and Miller (6) found that higher intakes of total fat and saturated fat were not significantly associated with CHD in cohort studies, but that various substitutions of PUFA for SFA had beneficial associations in randomised controlled trials (RCTs).
Mozaffarian et al.(7) in a meta-analysis of FA substitution RCTs which also failed to distinguish between omega 6 and omega 3 fatty acids stated that the method “cannot distinguish between potentially distinct benefits of increasing polyunsaturated fatty acids (PUFA) versus decreasing saturated fatty acids (SFA).”
RCTs conducted in the past to test this hypothesis did not produce conclusive results, but were suggestive of benefit from omega 3 fatty acids only (8). And clinical practice guidelines such as those published by the American College of Cardiology support the use of omega 3 fatty acid supplements (9).
Another common criticism of LCHF diets is the suggested linear correlation between LDL-cholesterol and ischemic heart disease mortality. However the effect of a distorted HDL-total cholesterol level appears to be a greater factor associated with IHD mortality by a factor of around 40% (10) and LCHF diets have demonstrated improved HDL-total cholesterol ratios.
Ketogenic diets, LCHF diets and cardiovascular markers
Randomised controlled trials continue to show that ketogenic diets tend to promote increases in HDL cholesterol and reduced triacylglycerol (TAG) levels and insulin with little difference in LDL, oxidised LDL or total cholesterol (11; 12; 13 ; 14)
More recently Westman and colleagues have evaluated differences in lipid sub-fractions between low-fat and low-carbohydrate, high-fat diets and found reductions in VLDL, medium and small size LDL, increases in large particle LDL although total LDL wasn’t reduced (15).
A review of RCTs including 447 participants found statistically significant reductions in triglycerides and improved high-density lipoprotein cholesterol in those following LCHF vs LFHC (Total cholesterol and low-density lipoprotein cholesterol values were reduced more in those following LFHC) (16). Recently Chiu and colleagues have demonstrated no appreciable difference in insulin sensitivity or plasma lipids or lipoproteins related to either saturated fat intake or protein intake in a lower carbohydrate diet (17).
There is little evidence to suggest that ketogenic diets, saturated fat or total fat intake play a causal role in cardiovascular or other disease, and the risks that have been associated with LCHF diets in general appear to rest more upon a priori systematic beliefs than on evidence. There is a concern that some sub-populations may have worsened LDL cholesterol levels but this is only likely to be a factor if extreme, or with a worsening of Apo-B / small particle LDL lipid sub-fractions and it warrants further research to determine the effects of various macronutrient compositions of diet on at-risk sub-groups with respect to lipid sub-fractions and indeed their effect on total and CVD mortality and morbidity.
1. Diabetes New Zealand. (2015). Low Carbohydrate Diet | Diabetes New Zealand.
2. Hooper, L., Summerbell, C. D., Thompson, R., Sills, D., Roberts, F. G., Moore, H., & Davey Smith, G. (2011). Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Database of Systematic Reviews(7), CD002137. doi: 10.1002/14651858.CD002137.pub2
3. Mente, A., de Koning, L., Shannon, H. S., & Anand, S. S. (2009). A systematic review of the evidence supporting a causal link between dietary factors and coronary heart disease. Arch Intern Med, 169(7), 659-669. doi: 10.1001/archinternmed.2009.38
4. Siri-Tarino, P. W., Sun, Q., Hu, F. B., & Krauss, R. M. (2010). Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. The American journal of clinical nutrition, 91(3), 535-546. doi: 10.3945/ajcn.2009.27725
5. Jakobsen, M. U., O'Reilly, E. J., Heitmann, B. L., Pereira, M. A., Balter, K., Fraser, G. E., . . . Ascherio, A. (2009). Major types of dietary fat and risk of coronary heart disease: a pooled analysis of 11 cohort studies. Am J Clin Nutr, 89(5), 1425-1432. doi: 10.3945/ajcn.2008.27124
6. Skeaff, C. M., & Miller, J. (2009). Dietary fat and coronary heart disease: summary of evidence from prospective cohort and randomised controlled trials. Annals of Nutrition & Metabolism, 55(1-3), 173-201. doi: 10.1159/000229002
7. Mozaffarian, D., Micha, R., & Wallace, S. (2010). Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of randomized controlled trials. PLoS Medicine, 7(3), e1000252. doi: 10.1371/journal.pmed.1000252
8. Ramsden, C. E., Zamora, D., Leelarthaepin, B., Majchrzak-Hong, S. F., Faurot, K. R., Suchindran, C. M., . . . Hibbeln, J. R. (2013). Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis. British Medical Journal, 346. doi: 10.1136/bmj.e8707
9. Mosca, L., Appel, L. J., Benjamin, E. J., Berra, K., Chandra-Strobos, N., Fabunmi, R. P., . . . Williams, C. L. (2004). Evidence-based guidelines for cardiovascular disease prevention in women 1. Journal of the American College of Cardiology, 43(5), 900-921. doi: 10.1016/j.jacc.2004.02.001
10. Prospective Studies Collaboration. (2007). Blood cholesterol and vascular mortality by age, sex, and blood pressure: a meta-analysis of individual data from 61 prospective studies with 55 000 vascular deaths. The Lancet, 370(9602), 1829-1839.
11. Foster, G. D., Wyatt, H. R., Hill, J. O., McGuckin, B. G., Brill, C., Mohammed, B. S., . . . Klein, S. (2003). A Randomized Trial of a Low-Carbohydrate Diet for Obesity. New England Journal of Medicine, 348(21), 2082-2090. doi: doi:10.1056/NEJMoa022207
12. A Randomized Trial Comparing a Very Low Carbohydrate Diet and a Calorie-Restricted Low Fat Diet on Body Weight and Cardiovascular Risk Factors in Healthy Women. (2003). The Journal of Clinical Endocrinology & Metabolism, 88(4), 1617-1623. doi: doi:10.1210/jc.2002-021480
13. Sharman, M. J., Kraemer, W. J., Love, D. M., Avery, N. G., Gómez, A. L., Scheett, T. P., & Volek, J. S. (2002). A Ketogenic Diet Favorably Affects Serum Biomarkers for Cardiovascular Disease in Normal-Weight Men. The Journal of Nutrition, 132(7), 1879-1885.
14. Yancy, J. W. S., Olsen, M. K., Guyton, J. R., Bakst, R. P., & Westman, E. C. (2004). A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat Obesity and HyperlipidemiaA Randomized, Controlled Trial. Annals of Internal Medicine, 140(10), 769-777. doi: 10.7326/0003-4819-140-10-200405180-00006
15. Westman, E. C., Yancy Jr, W. S., Olsen, M. K., Dudley, T., & Guyton, J. R. (2006). Effect of a low-carbohydrate, ketogenic diet program compared to a low-fat diet on fasting lipoprotein subclasses. International Journal of Cardiology, 110(2), 212-216. doi: http://dx.doi.org/10.1016/j.ijcard.2005.08.034
16. Nordmann, A. J., Nordmann, A., Briel, M., & et al. (2006). Effects of low-carbohydrate vs low-fat diets on weight loss and cardiovascular risk factors: A meta-analysis of randomized controlled trials. Archives of Internal Medicine, 166(3), 285-293. doi: 10.1001/archinte.166.3.285
17. Chiu, S., Williams, P. T., Dawson, T., Bergman, R. N., Stefanovski, D., Watkins, S. M., & Krauss, R. M. (2014). Diets High in Protein or Saturated Fat Do Not Affect Insulin Sensitivity or Plasma Concentrations of Lipids and Lipoproteins in Overweight and Obese Adults. The Journal of Nutrition, 144(11), 1753-1759. doi: 10.3945/jn.114.197624