What is cholesterol?

What is cholesterol? Since the 1960s, when it was linked to heart disease, cholesterol has been a topic for concern.

What is cholesterol?

What is cholesterol?

Since the 1960s, when it was linked to heart disease, cholesterol has been a topic for concern. However, getting back to the basics of this often-misunderstood compound is vital, as it is a molecule which is essential for survival and health.

Cholesterol is a unique compound, as it is found in almost all cells and has multiple functions within the human body, including the production of hormones and for the functioning of nerve cells. Most of the cholesterol in the body is made in the liver, but we also obtain cholesterol from animal-based foods such as meat, eggs and dairy produce.1

It has been suggested that a diet high in saturated fats causes an increase in a type of cholesterol often referred to as LDL. Around one in six people in the UK are thought to have raised cholesterol, although many remain undiagnosed and therefore untreated.2,3 However, to understand the effects of cholesterol on the health of the heart, it is important to understand the ‘types’ of cholesterol present in the body.

LDL refers to a combination of cholesterol and a protein. LDL (low density lipoprotein) carries cholesterol to the cells of the body. However, when cholesterol levels are raised, LDL causes the deposition of cholesterol in the blood vessels. This leads to a narrowing of the blood vessel walls and the increased chance of a blockage. Oxidised LDL is particularly harmful and is strongly linked to the development of heart disease.4

There is another form of cholesterol, called HDL (high density lipoprotein) which is often referred to as ‘good’ cholesterol. This is involved in carrying cholesterol away from the blood vessels and to the liver for removal. Whilst overall cholesterol level is often a marker for the risk of heart disease, many practitioners will now also consider the balance between LDL, HDL and triglycerides in an effort to assess individual risk and determine the best form of treatment. The determination of whether cholesterol level is high and requires intervention will depend on what other risk factors are present but is currently set at 5mmol/L but may be reduced to 4mmol/L if someone has other factors such as hypertension or obesity as well.

Causes of high cholesterol

There are several risk factors for the development of high cholesterol, only some of which can be controlled. Obesity and an increased fat mass have been shown to have a significant effect on cholesterol. A higher fat mass and particularly a high waist circumference is linked to higher circulating fats.5 This has been shown, along with high LDL cholesterol, to be a significant risk factor. Higher fat mass is also associated with an increase in the production of inflammatory compounds, which can then cause the accumulation of cholesterol.

There is also a condition known as familial hypercholesterolaemia or FH which causes LDL and total cholesterol to be higher than normal. The NHS estimates that up to 1 in 250 people in the UK have this condition and currently only around 8% of these people have been identified and are therefore being monitored and treated.6 The cause is genetic, and it affects the ability of the body to clear LDL from the blood. Therefore treatment is essential to reduce the increased risk of developing early onset heart disease.

Diet and lifestyle

In terms of cholesterol, there are many options for dealing with any excess in the body. Very low-fat diets and the omission of eggs were often recommended in the past, but these recommendations have changed. Low fat ‘diet’ foods are often best avoided due to their reliance on sugar to provide taste as studies have now linked sugar to an increased risk of heart disease.

A Mediterranean style diet is probably one of the most relevant,7 as it focuses on polyphenol, potassium and magnesium rich fruits and vegetables, foods such as nuts and seeds which contain both omega 3 and 6 fatty acids, olive oil and lean meats and oily fish, such as herring, mackerel, salmon and sardines which are also rich in omega 3 fats. Processed foods are discouraged, and the emphasis is on the consumption of fresh, unprocessed or minimally processed foods which are naturally much lower in sugar, salt and trans and hydrogenated fats.8 This diet has been shown to lower cholesterol in overweight people.9

This diet has also been shown to support a range of bacteria in the gut, which is associated with improved levels of good cholesterol. This is likely due to the high levels of plant foods included. These foods are also fibre rich which can decrease the amount of fats and animal proteins consumed, which will also positively influence the microbiome.10

Regular physical activity has been shown to increase HDL, which reduces the risk of heart disease by around 40%.11 Exercise appears to allow muscle to use excess fat for energy.

Nutrients for support

Omega 3 fatty acids, especially the EPA and DHA found in oily fish, should also be considered to support heart health.12,13 Data shows that the intake of oily fish is low in the UK and omega 3 intakes are particularly poor when compared to other fats. A combined intake of 250mg of EPA and DHA can contribute to normal heart function. Evidence suggests that a sufficient intake can lower triglycerides by decreasing the production and increasing the clearance of VLDL, can lower cholesterol absorption and synthesis, increase HDL and improve the ratio of total cholesterol to HDL.14

In terms of cholesterol reduction, taking plant sterols and stanols has been shown to be useful, as plant sterols are structurally similar to cholesterol and appear to competitively inhibit the absorption of both dietary and biliary cholesterol in the gut.15 Taking a level of around 2g a day either from foods such as vegetables, grains and legumes or from a supplement, can help to reduce cholesterol and may even be useful for familial hypercholesterolaemia.

Garlic is another ingredient which is useful for hypercholesterolaemia. Garlic has positive effects on both total cholesterol and triglyceride levels16,17 as well as reducing the oxidation of cholesterol.18

Other supplements which are often recommended for high cholesterol include:

  • Lecithin (which encourages the excretion of cholesterol19). Studies suggest a reduction in LDL cholesterol and an increase in HDL with lecithin supplementation.20
  • Artichoke Leaf Extract (ALE) – appears to increase the excretion of cholesterol. Meta-analysis shows that ALE reduces LDL and total cholesterol as well as triglycerides.21,22
  • Astaxanthin – a carotenoid, which is obtained naturally from fresh water green microalgae Haematococcus pluvialis, appears to slow LDL oxidation.23,24

For those on medications

Finally, for those already using medication, CoQ10 is particularly relevant. Statins work by decreasing cholesterol via an enzyme but this also reduces CoQ10 production.25 CoQ10 supplementation has been shown to reduce many of the side effects of statin use, including muscle pain and fatigue.26

References

  1. Russell DW. Cholesterol biosynthesis and metabolism. Cardiovasc Drugs Ther. 1992;6(2):103-10.
  2. HSIS. State of the Nation: Dietary Trends in the UK 20 Years On. 2019. Available at: https://www.hsis.org/wp-content/uploads/2019/08/HSIS-report-2019-artwork-screen-res.pdf
  3. Public Health England. Health Matters: Preventing Cardiovascular Disease. 2019.
  4. Charach G, George J, Afek A, et al. Antibodies to oxidized LDL as predictors of morbidity and mortality in patients with chronic heart failure. J Card Fail. 2009;15(9):770-4.
  5. Piché ME, Poirier P, Lemieux I, Després JP. Overview of epidemiology and contribution of obesity and body fat distribution to cardiovascular disease: an update. Prog Cardiovasc Dis. 2018;61(2):103-113.
  6. Barkas F, Nomikos T, Liberopoulos E, Panagiotakos D. Diet and cardiovascular disease risk among individuals with familial hypercholesterolemia: systematic review and meta-analysis. Nutrients. 2020;12(8):2436.
  7. Martínez-González MA, Gea A, Ruiz-Canela M. The Mediterranean diet and cardiovascular health. Circ Res. 2019;124(5):779-798.
  8. Barbagallo CM, Cefalù AB, Gallo S, et al. Effects of Mediterranean diet on lipid levels and cardiovascular risk in renal transplant recipients. Nephron. 1999;82(3):199-204.
  9. Meslier V, Laiola M, Roager HM, et al. Mediterranean diet intervention in overweight and obese subjects lowers plasma cholesterol and causes changes in the gut microbiome and metabolome independently of energy intake. Gut. 2020;69(7):1258-1268.
  10. McDonald D, Hyde E, Debelius JW, et al. American Gut: an open platform for citizen science microbiome research. mSystems. 2018;3(3).
  11. Lira F, Yamashita A, Uchida M, et al. Low and moderate, rather than high intensity strength exercise induces benefit regarding plasma lipid profile. Diabetol Metab Syndr. 2010;2:31.
  12. de Leiris J, de Lorgeril M, Boucher F. Fish oil and heart health. J Cardiovasc Pharmacol. 2009;54(5):378-384.
  13. Siscovick DS, Barringer TA, Fretts AM, et al. Omega-3 polyunsaturated fatty acid (fish oil) supplementation and the prevention of clinical cardiovascular disease: a science advisory from the American Heart Association. Circulation. 2017;135(15).
  14. Natural Medicines Comprehensive Database. Fish Oil Mechanism of Action. 2010.
  15. Kamal-Eldin A, Moazzami A. Plant sterols and stanols as cholesterol-lowering ingredients in functional foods. Recent Pat Food Nutr Agric. 2009;1(1):1-14.
  16. Mathew BC, Prasad NV, Prabodh R. Cholesterol-lowering effect of organosulphur compounds from garlic: a possible mechanism of action. Kathmandu Univ Med J. 2004;2:100–102.
  17. Orekhov AN, Tertov VV. In vitro effect of garlic powder extract on lipid content in normal and atherosclerotic human aortic cells. Lipids. 1997;32:1055–1060.
  18. Asdaqa SM, Inamdar MN. Potential of garlic and its active constituent, S-allyl cysteine, as antihypertensive and cardioprotective in presence of captopril. Phytomedicine. 2010;17(13):1016-1026.
  19. Calabresi L, Franceschini G. Lecithin:cholesterol acyltransferase, high-density lipoproteins, and atheroprotection in humans. Trends Cardiovasc Med. 2010;20(2):50–53.
  20. LeBlanc MJ, Brunet S, Bouchard G, et al. Effects of dietary soybean lecithin on plasma lipid transport and hepatic cholesterol metabolism in rats. J Nutr Biochem. 2003;14(1):40-8.
  21. Gebhardt R. Inhibition of cholesterol biosynthesis in HepG2 cells by artichoke extracts is reinforced by glucosidase pretreatment. Phytother Res. 2002;16:368–72.
  22. Sahebkar A, Pirro M, Banach M, Mikhailidis DP, Atkin SL, Cicero AFG. Lipid-lowering activity of artichoke extracts: a systematic review and meta-analysis. Crit Rev Food Sci Nutr. 2018;58(15):2549-2556.
  23. Iwamoto T, Hosoda K, Hirano R, et al. Inhibition of low-density lipoprotein oxidation by astaxanthin. J Atheroscler Thromb. 2000;7:216–222.
  24. Ursoniu S, Sahebkar A, Serban MC, Banach M. Lipid profile and glucose changes after supplementation with astaxanthin: a systematic review and meta-analysis of randomized controlled trials. Arch Med Sci. 2015;11:253–266.
  25. Ghirlanda et al. Evidence of plasma CoQ10-lowering effect by HMG-CoA reductase inhibitors: a double-blind, placebo-controlledstudy. J Clin Pharmacol. 33 (1993), pp226-229.
  26. Bargossi et al. Exogenous CoQ10 supplementation prevents plasma ubiquinone reduction induced by HMG-CoA reductase inhibitors. Mol Aspects of Medicine, Vol 15, Supplement 1 (1994) pp s187-s193
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