So if you read Part One of this blog (and if you haven't I suggest you do it now!) then I hope I have begun to convince you that perhaps saturated fat doesn’t cause heart disease and perhaps refined carbohydrates or sugars might. In this blog I’m going to help you work out if you have good metabolic health and give you a better understanding of cholesterol, lipoproteins and triglycerides which are all blood lipid or fat markers that your doctor will check when looking at cardiovascular risk.
It is true that saturated fat can raise blood levels of total cholesterol but it is not the problem that you might think it is. The Framingham Heart Study, that I mentioned in Part 1 of this blog, showed that in men over 50, and in women generally, there was no association between elevated total cholesterol and cardiovascular disease. Lets repeat that for clarity, increased total cholesterol is not associated with increased cardiovascular risk. But cholesterol is also vitally important for your health especially as you age.
Cholesterol plays a key roles in building the membranes of every single cell in your body; your brain and nervous system require lots of cholesterol to work effectively; cholesterol is what is converted by the sun in your skin to make vitamin D; your sex hormones oestrogen, progesterone and testosterone are all made from cholesterol; and you need cholesterol to make bile acids to help digest your food, There are plenty of studies showing that as we age cholesterol is in fact protective. High total cholesterol levels are associated with a whole range of better health outcomes including with cognition, frailty, even cardiac arrest and overall mortality (death again!). Reductions in cholesterol are also associated with worsening health.
Lipoproteins
HDL (high density lipoproteins) and LDL (low density lipoproteins) have the job of transporting fat in the form of cholesterol and triglycerides around the body. HDL has generally been thought of as "good" and LDL as "bad" but it is not quite that simple.
Fat and water don't mix so in order to transport fat in the blood it needs to be attached to a lipoprotein molecule. The protein part of the molecule allows the body's cells to recognise it and deal with it appropriately. Lipoproteins also help to transport fat soluble vitamins, they help the body to fight infections, they transport key antioxidants like CoQ10 and they are essential for cell repair and cell structure.
When scientists looked at LDL against mortality (death) in large population studies they found that having a very low LDL increased the risk or mortality the most.
Sung, K.-C.; Huh, J.H.; Ryu, S.; Lee, J.-Y.; Scorletti, E.; Byrne, C.D.; Kim, J.Y.; Hyun, D.S.; Ko, S.-B. Low Levels of Low-Density Lipoprotein Cholesterol and Mortality Outcomes in Non-Statin Users. J. Clin. Med.2019, 8, 1571. https://doi.org/10.3390/jcm8101571
LDL is like a delivery van, it transports fat (cholesterol and triglycerides) out of the liver and takes it to where it is needed in the body. It starts off as very low density (buoyant) large LDL and as it off loads fat it becomes smaller and more dense and eventually it returns to the liver where it is recycled. HDL is the returns van, it takes fat from the tissues to the liver, on its journey it picks up fat and it slowly becomes larger and more buoyant.
So you can see that LDL is made up of particles of different size and density as it off loads fat. Small-dense LDL particles are more susceptible to oxidation and damage resulting in them becoming pro-atherogenic (meaning it contributes to fatty deposits in the arteries) pro-thrombotic (leading to blood clots), and pro-inflammatory. But large buoyant LDL may be resistant to oxidation and may even be anti-atherogenic and help prevent these health issues.
So it may not be the measure of total LDL that matters but rather the proportion of large to small particles that is important. Indeed a high concentration of small-dense LDL and a low concentration of large buoyant LDL has been associated with greater risk of coronary heart disease. The good news is that trial data suggests that eating saturated fats can decrease small-dense LDL and increases large buoyant LDL. So again we find that eating saturated fat might actually be protective against coronary heart disease.
The biggest problem as mentioned above is if small dense LDL gets damaged. If it is is damaged then the liver no longer recognises it and it can't be recycled, so it offloads its fat and continues to circulate becoming even more damaged. Scientists know that is is this small dense damaged LDL can get stuck in arteries contributing to heart disease. LDL is damaged by high blood sugar, highly refined vegetable oils, smoking and inflammation. So again you can see why a low carb diet rich in real whole foods and avoiding processed foods is a heart healthy one!
Triglycerides
Lastly, let's take a look at triglycerides which is another metabolic health marker that your GP will check. Triglycerides (TGs) are considered an independent risk factor for cardiovascular disease (CVD). When TGs are elevated there is an increased CVD risk. A 2020 meta-analysis looked at 12 randomized studies and found that a low-carbohydrate diet was associated with a decrease in triglyceride levels. In particular one well designed study known as the DIETFIT study set out to evaluate the associations between changes in percentage of dietary saturated fat intake (%SFA) and changes in LDL, HDL, and triglyceride concentrations for those following a healthy low-carbohydrate (HLC) diet. They found than an increase in the percentage of saturated fat, without significant changes in absolute saturated fat intake, over 12 months was associated with a statistically significant decrease in triglycerides in the context of a weight-loss study in which participants simultaneously decreased carbohydrate intake”. So yet again a low carb diet including saturated fats is good for you!
Good Metabolic Health
So lets look at what you want your blood results to be showing for you to have good metabolic health. You want to have:
A waist circumference less than 90cm (35.5 inches) for men and less than 80cm (31.5 inches) for women or a waist to hip ratio of less than 0.9 in men and 0.85 in women.
Triglycerides less than 1.7mmol/L
Fasting (HDL)-cholesterol more than 1.03mmol/L for men and 1.29mmol/L for women
Blood pressure (BP) less than 130/85 mmHg
Plus, you want to be insulin sensitive and not insulin resistant (but this is often not measured) and have a fasting blood glucose of less than 5.6mmol/L.
You can also look at the ratio of TC/HDL ratio which is a better predictor of CHD risk than TC or HDL alone.
Interestingly although LDL will be checked it is not usually included in the risk calculators that GPs use to assess heart disease. However, if you want a guide then studies tend to suggest that an LDL of around 3.6mmol/L might be optimum. If you are very concerned about your risk of heart disease it is possible to ask your GP for a lipoprotein sub-fraction test and this can show up if you have any of the damaged low density LDL. In addition you could think about getting a coronary calcium scan which checks for deposits or build-up of plaque on the walls of your coronary arteries, you are likely to have to pay privately for this.
Diet, Saturated Fat & Sugar
So to come back to diet, research suggests that increasing saturated fat consumption along with reducing sugar intake can lead to improvements in metabolic health. One of the reasons for this is that carbohydrates, especially refined carbohydrates like sugar and flour, can cause spikes in blood sugar and insulin levels. Over time, this can lead to insulin resistance, which is a major contributor to obesity, diabetes, and other health problems. A diet high in added sugars has been found to cause a 3-fold increased risk of death due to cardiovascular disease. You can read more about insulin resistance here. Remember that you want to be eating real whole fats too like butter, lard, coconut, olive oil and fatty meats and avoiding highly processed vegetables oils and margarines.
Summary
It seems clear that our dietary guidelines need to shift focus away from reducing saturated fat, and from replacing saturated fat with carbohydrates, especially high processed and refined carbohydrates. Despite the growing evidence supporting the benefits of a low-carbohydrate, high-fat diet, the low-fat dogma still persists even in professional circles. It takes 17 years for new research to be implemented as clinical practice, perhaps we are just about to see that happen! It can’t happen soon enough in my view.
If you want to use fat as a fuel to help address a chronic disease, help you drop a few pounds or get more energy then you can download my Quick Start Keto Guide For Fatigue (but it will help do the rest too!) https://www.moiranewiss.co.uk/quick-start-keto-guide-for-fatigue
Disclaimer: Before changing your diet or lifestyle and taking any supplements always seek the advice of your doctor or another suitably qualified professional such as a nutritional therapist. The content of this blog is for informational purposes only and is not a substitute for professional medical advice. Always seek the advice of your doctor with regards to any questions you have about a medical condition.
References
DiNicolantonio J. J, Lucan S. C, an O'Keefe J. H. (2016) "The Evidence for Saturated Fat and for Sugar Related to Coronary Heart Disease." Prog Cardiovasc Dis. 58(5):464-72. doi: 10.1016/j.pcad.2015.11.006. Epub 2015 Nov 18. PMID: 26652233.
Dong T. et al (2020) The effects of low-carbohydrate diets on cardiovascular risk factors: A meta-analysis. PLoS One. 14;15(1):e0225348. doi: 10.1371/journal.pone.0225348. PMID: 31935216; PMCID: PMC6959586.
Eckel R. H,. et al. (2014) "2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines." J Am Coll Cardiol. 1;63(25 Pt B):2960-84. doi: 10.1016/j.jacc.2013.11.003. Epub 2013 Nov 12. PMID: 24239922.
Feinman R. D. et al (2015) "Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base." Nutrition. 31(1):1-13. doi: 10.1016/j.nut.2014.06.011. Epub 2014 Jul 9. PMID: 25287761.
Fitzgerald, D. (2020). "World McBride P. Triglycerides and risk for coronary artery disease. Curr Atheroscler Rep. 10(5):386-90. doi: 10.1007/s11883-008-0060-9. PMID: 18706279.War II and the Quest for Time-Insensitive Foods." Osiris, 35.
Jeong S. M et al. (2018) Association of change in total cholesterol level with mortality: A population-based study. PLoS One. 13(4):e0196030. doi: 10.1371/journal.pone.0196030. Erratum in: PLoS One. 2019 Apr 18;14(4):e0215934. PMID: 29672595; PMCID: PMC5908176.
Johannesen C. D. L, et al. (2020) Association between low density lipoprotein and all cause and cause specific mortality in Denmark: prospective cohort study, BMJ; 371 :m4266 doi:10.1136/bmj.m4266
Kassi, E. et al. (2011) Metabolic syndrome: definitions and controversies. BMC Med 9, 48. https://doi.org/10.1186/1741-7015-9-48
Kim J. H. (2019) Effects of cholesterol levels on outcomes of out-of-hospital cardiac arrest: a cross-sectional study. Clin Exp Emerg Med. 6(3):242-249. doi: 10.15441/ceem.18.057. Epub 2019 Sep 30. PMID: 31571440; PMCID: PMC6774009.
Lustig R. H, Schmidt L. A, and Brindis C. D. (2012) "Public health: The toxic truth about sugar." Nature. 1;482(7383):27-9. doi: 10.1038/482027a. PMID: 22297941.
Lv Y. B. (2019) Triglycerides Paradox Among the Oldest Old: "The Lower the Better?". J Am Geriatr Soc. 67(4):741-748. doi: 10.1111/jgs.15733. Epub 2019 Jan 10. PMID: 30628728; PMCID: PMC6458070.
Malhotra A, Redberg R. F, and Meier P. (2017) Saturated fat does not clog the arteries: coronary heart disease is a chronic inflammatory condition, the risk of which can be effectively reduced from healthy lifestyle interventions. Br J Sports Med. 51(15):1111-1112. doi: 10.1136/bjsports-2016-097285. Epub 2017 Apr 25. PMID: 28442474.
Morris Z. S, Wooding S, and Grant J. (2011) The answer is 17 years, what is the question: understanding time lags in translational research. J R Soc Med. 104(12):510-20. doi: 10.1258/jrsm.2011.110180. PMID: 22179294; PMCID:
Shih C. W. et al. (2019) Changes in blood lipid concentrations associated with changes in intake of dietary saturated fat in the context of a healthy low-carbohydrate weight-loss diet: a secondary analysis of the Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) trial. Am J Clin Nutr. Feb 1;109(2):433-441. doi: 10.1093/ajcn/nqy305. Erratum in: Am J Clin Nutr. 2020 Feb 1;111(2):490. PMID: 30649213; PMCID: PMC6367958.PMC3241518.
Siri-Tarino P. W, et al. (2010) "Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease." Am J Clin Nutr. 91(3):535-46. doi: 10.3945/ajcn.2009.27725. Epub 2010 Jan 13. PMID: 20071648.
Siri-Tarino P. W. et al. (2010) Saturated fatty acids and risk of coronary heart disease: modulation by replacement nutrients. Curr Atheroscler Rep. 12(6):384-90. doi: 10.1007/s11883-010-0131-6. PMID: 20711693; PMCID: PMC2943062.
Sung, K.-C. et al. (2019). Low Levels of Low-Density Lipoprotein Cholesterol and Mortality Outcomes in Non-Statin Users. J. Clin. Med. 8, 1571. https://doi.org/10.3390/jcm8101571
Teicholz, N (2023). A short history of saturated fat: the making and unmaking of a scientific consensus. Current Opinion in Endocrinology & Diabetes and Obesity 30(1):p 65-71, doi: 10.1097/MED.0000000000000791
Valk R. et al. (2022) Hammill J, Grip J. Saturated fat: villain and bogeyman in the development of cardiovascular disease? Eur J Prev Cardiol. 21;29(18):2312-2321. doi: 10.1093/eurjpc/zwac194. PMID: 36059207.
Volek J. S. et al (2009) "Carbohydrate Restriction has a More Favorable Impact on the Metabolic Syndrome than a Low Fat Diet." Lipids. 44(4):297-309. doi: 10.100
Wang M. C. et al. (2019) Plasma lipid concentrations and survival in geriatric population: A retrospective cohort study. Medicine (Baltimore). 98(49):e18154. doi: 10.1097/MD.0000000000018154. PMID: 31804326; PMCID: PMC6919530.
Yang Q. et al (2014) "Added sugar intake and cardiovascular diseases mortality among US adults." JAMA Intern Med. 174(4):516-24. doi: 10.1001/jamainternmed.2013.13563. PMID: 24493081.
Yi S.W, Yi J.J, and Ohrr H. (2019) Total cholesterol and all-cause mortality by sex and age: a prospective cohort study among 12.8 million adults. Sci Rep. 7;9(1):1596. doi: 10.1038/s41598-018-38461-y. PMID: 30733566; PMCID: PMC6367420.