Understanding your cholesterol levels

Raised cholesterol is a common finding. In fact, according to the World Health Organisation, 39% of adults worldwide were thought to have raised total cholesterol levels in 2008; a figure which is likely to have increased significantly over the last decade. Elevated cholesterol levels are a risk factor for coronary heart disease, which is the leading cause of premature deaths in the UK and Ireland. As such, it is at the forefront of preventative medicine to identify and reduce high cholesterol levels.

So, what is cholesterol, and why is it so important?

Cholesterol is a fat chemical made by the liver and other cells of the body. It is carried around the bloodstream by particles called lipoproteins. Contrary to what you may think, some cholesterol is essential for good health and is an important component of many bodily functions. For example:

• It makes up part of the structure of cell membranes, the protective capsule which surrounds every cell in the body, without which they could not function.
• Cholesterol is used to make various hormones in the body, such as testosterone, progesterone and cortisol, and is also essential for vitamin D production.
• Cholesterol enables the body to form bile acids which are needed to break down fats in the digestive tract.

However, elevated levels of cholesterol contribute to the development of atherosclerosis and increase the risk of coronary heart disease. Atherosclerosis is a thickening, or hardening, of the arteries caused by a build-up of plaque. If these plaques are left untreated, they can cause heart attacks or strokes.

What causes high cholesterol?

For most people high cholesterol is caused by lifestyle habits. These include, eating fatty foods, being overweight, not exercising regularly, smoking and drinking alcohol.

Rarely, it is caused by a genetic problem with the way cholesterol is made in the body. This causes high cholesterol to run in families. There are other medical conditions which can cause high cholesterol, such as an underactive thyroid, some rare kidney and liver problems, and in women, early menopause.

How to Interpret your Cholesterol Results:

A cholesterol blood test provides a breakdown of the different types of cholesterol in your bloodstream. Interpreting these correctly helps to understand your own risk of heart disease or stroke.

A cholesterol blood panel is broken down into the following components, which we’ll explore in more detail below:

• Total Cholesterol
• HDL Cholesterol
• Triglycerides
• LDL Cholesterol
• Cholesterol: HDL Ratio

Total Cholesterol and LDL cholesterol

Scientists first noted an association between elevated total cholesterol and coronary heart disease (CHD) in the early 20th Century. This was confirmed in following years by multiple, long-term observational studies, such as the Framingham Heart2 which was established in 1948. This ground-breaking study has followed the development of CHD over decades in three generations of participants. As a result, there is now a good understanding of the modifiable risk factors for CHD. Elevated total cholesterol levels were identified as a major risk factor for CHD, and increased LDL levels have the most evidence for causing CHD. In fact, studies have documented the presence of LDL cholesterol deposited in the atherosclerotic lesions which cause heart attacks and strokes3. Interestingly, in populations where the average total cholesterol or LDL is low, there is a low incidence of CHD, despite the fact there is a high prevalence of other major risk factors, such as high blood pressure or cigarette smoking4. This indicates that reducing total cholesterol and LDL cholesterol is one of the most significant ways to reduce your cardiovascular risk.

High-Density Lipoprotein (HDL)

HDL is thought to reduce the risk of coronary heart disease and be cardioprotective, due to multiple mechanisms which have a positive effect on heart health.

These include:

• Removing LDL cholesterol from the atherosclerotic plaques in arteries and transporting it back to the liver where it is removed from the body.
• It has an anti-inflammatory effect and protects the artery walls from damage by LDL cholesterol.
• It has an anti-oxidant effect which helps protect cells and important chemical messengers in the blood and tissues from being broken down.

The relationship between HDL cholesterol and CHD was first noted in the 1950s. It was noted that patients with low HDL levels, were more likely to have CHD5. Further larger-scale studies have confirmed this and shown that with each 1-mg/dL reduction in HDL cholesterol there was an associated 2-3% increased risk of CHD, whereas each 1-mg/dL increase in HDL was associated with a 6% lower risk of death from a coronary event6. This means that HDL cholesterol levels should be high to reduce the risk of CHD.

Triglycerides

When you eat, the body uses glucose from your meals for energy. Any calories which are not used immediately are converted into triglycerides and stored in your fat cells. Triglycerides are released for energy between meals. If you regularly eat more calories than you burn, particularly from high-carbohydrate foods, you may have high triglycerides.

High triglycerides are thought to be a risk factor for CHD; however, the evidence isn’t as strong as for LDL and HDL cholesterol, and it is thought to be a stronger risk factor in women than men. This is because people with high triglycerides often have a low HDL level, so it’s hard to know how much the high triglycerides impact your risk of heart disease(2).

However, the strongest evidence comes from a meta-analysis which looked at the findings of 6 major studies, including the Framingham Heart Study2. It found that even when HDL levels are accounted for, each 1mmol/L increase in triglyceride level, causes a 37% increase in risk of CHD in women, and a 14% increase in risk for men7.

Cholesterol: HDL Ratio

This is the ratio of HDL compared to total cholesterol, and should be as low as possible, ideally less than 6.

How can high cholesterol be treated?

Lifestyle changes are at the forefront of treating high cholesterol. Making these changes can significantly reduce your cholesterol levels.

1. Dietary Changes for high cholesterol

Although genetics play a role in cholesterol levels, lifestyle, and particularly dietary habits, account for most of the differences in cholesterol levels among adults1. Making dietary changes can reduce your cholesterol levels and improve your risk of CHD. The following dietary changes are shown to improve cholesterol levels:

• Reduce Saturated Fatty Acids, mainly found in meat and dairy products

Saturated fatty acids are a major contributor to total cholesterol and LDL levels. Studies have shown a high correlation between the amount of SFAs in the diet with both elevated total cholesterol levels and a higher rate of both fatal and non-fatal coronary heart disease. As such, reducing SFAs is one of the most important dietary changes to make. They are found mainly in animal food sources, such as red meat and dairy products, as well as some tropical plant oils like palm and coconut oil8.

• Increase foods rich in Linoleic Acid, such as soya protein, seeds and nuts,

Linoleic acid reduces cholesterol levels by improving the liver’s ability to remove LDL cholesterol from the bloodstream. Once in the liver it is removed from the body in the bile.

• Increase Omega-3 fatty acids, found in fatty fish, and vegetable oils such as canola oil or soybean oils.

The unique relationship between Omega-3 fatty acids and cardiovascular health was first noted in the 1950s, when studying the dietary habits of Innuits in Greenland9. The diet of Innuits is traditionally high in fatty meats from sea mammals and fish, however, they have a low rate of CHD. This was attributed to the high level of Omega-3 fatty acids in the fish oils. Eating fatty fish 2-3 times per week or taking a daily fish oil supplement can effectively reduce your risk of CHD.

• Increase soluble fibre found oats, fruits, vegetables beans and legumes.

Soluble fibres bind to the cholesterol in your gut (which has been removed from the liver in bile salts) and stops it being reabsorbed back into the circulation.

• Plant Stanols or Sterols

Plant sterols are substances that are similar to cholesterol but are made in plants. They are found in vegetable oils, nuts, and seeds. Plant sterols can help reduce cholesterol levels by limiting the amount of cholesterol that is able to enter the body. Adding 2g plant sterols to the diet each day can reduce LDL cholesterol by 9-14%10.

An easy way to add these foods into your diet is to follow the Portfolio Diet. The portfolio diet is an evidenced- based diet which has been shown to reduce LDL cholesterol by 17%, and total cholesterol by 12%, similar results to taking a statin medication.

In the Portfolio Diet you should aim to incorporate these four foods in your diet each day. Each of these foods will individually reduce your LDL cholesterol, but the effect is enhanced when eaten together. The foods to include daily are

1. Soya protein
2. Oats or barley which contain beta- glucans.
3. Plant sterols or stanols
4. Tree nuts

You can read more about the Portfolio Diet in this handout.

2) Smoking Cessation for high cholesterol

Cigarette smoking is a major risk factor for cardiovascular disease. It exerts various mechanisms which make CVS disease more likely but one of the most important is its effect on HDL cholesterol. Studies on men and women who smoked 20 or more cigarettes per day were found to have 11-14% lower HDL levels than non- smokers. The difference was more marked in heavy smokers. However, it was found that people who stop smoking see a rapid increase in HDL within as little as 30 days, showing that it’s never too late to see the benefits of smoking cessation11-13.

3) Physical Exercise for high cholesterol

Regular exercise reduces CHD risk in various way, one which is improving cholesterol levels. Interestingly, studies show that regular aerobic exercise (30-60 minutes of moderate intensity exercise three times weekly) can increase HDL cholesterol levels by 4-5%, whereas it is not shown to significantly reduce LDL cholesterol levels14-17.

When to start a Statin medication and do you really need one?

In some patients, a statin medication is advised to help reduce cholesterol levels. This would be recommended in all patients who’ve had a previous heart attack or stroke, but in most people, it is prescribed to help prevent these diseases occurring in the first place, called primary prevention. Interestingly, it’s not just your cholesterol levels which dictate whether you need a statin or not.

Other risk factors are taken into consideration, such as age, gender and ethnicity, and other health problems such as diabetes and high blood pressure. We can use this data to predict your QRISK which estimates your risk of having a heart attack or stroke in the next 10 years. If your risk is estimated to be over 10%, a statin would be suggested alongside lifestyle interventions.

If you would like a better understanding of your cholesterol levels and risk of Coronary Heart Disease, book in for a Well Woman or Well Man check with one of our expert doctors.

At One5 Health We use predictive algorithms to check not just your current levels but also are able to calculate your Heart Age so see if you ahead, in line with or behind the curve when it comes to your cardiovascular health.

Book a Well Woman or Well Man Check today to better understand your cholesterol levels and holisitc health with a lifestyle plan personalised to your results.

References:

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2. Manalo-Estrella P, Cox GE, Taylor CB. Atherosclerosis in rhesus monkeys VII. Mechanisms of hypercholesterolemia: hepatic cholesterolgenesis and the hypercholesterolemic threshold of dietary cholesterol. Arch Pathol. 1963;76:413-423. 7.

3. Kao VC, Wissler RW. A study of the immunohistochemical localization of serum lipoproteins and other plasma protein in human atherscherotic lesions. Exp Mol Pathol. 1965;4:465-470.

4. Keys A. Coronary heart disease—the global picture. Atherosclerosis. 1975;22:149-152.

5. Barr DP, Ross EM, Eder HA. Protein-lipid relationships in human plasma. Am J Med. 1951;11:480-493

6. Gordon DJ, Probstfield JL, Garrison RJ, et al. High-density lipoprotein cholesterol and cardiovascular disease: four prospective American studies. Circulation. 1989;79:8-19.

7. Hokanson JE, Austin MA. Plasma triglyceride level is a risk factor for cardiovascular disease independent of high-density lipoprotein cholesterol level: a meta-analysis of population-based prospective studies. J Cardiovasc Risk. 1996;5:213-219.

8. Keys A, ed. Coronary Heart Disease in Seven Countries. Monograph No. 29. Dallas, TX; American Heart Association; 1970.

9. Bang HO, Dyerberg J. Lipid metabolism and ischemic heart disease in Greenland Eskimos. In: Draper HH, ed. Advances in Nutrition Research. New York, NY: Plenum; 1980:1-22

10. Law M. Plant sterol and stanol margarine and health. BMJ. 2000;320:861-864

11. Kannell WB. Update on the role of cigarette smoking in coronary artery disease. Am Heart J. 1981;101:319-328.

12. Goldbourt J, Medalie JH. Characteristics of smokers, nonsmokers, and exsmokers among 10,000 adult males in Israel II. Physiologic biochemical, and genetic characteristics. Am J Epidemiol. 1997;105: 75-84.

13. Craig W, Palomaki G, Haddow J. Cigarette smoking and serum lipids and lipoprotein concentrations: analysis of published data. BMJ. 1989;298:784-788.

14. Kodama S, Tanaka S, Saito K, et al. Effects of aerobic exercise training on serum levels of high-density lipoprotein cholesterol: a meta-analysis. Arch Intern Med. 2007;167:999-1008. vol. 3 • no. 4 American Journal of Lifestyle Medicine 273

15. Durstine SL, Grandjean PW, Cox CA, Thompson PD. Lipids, lipoproteins, and exercise J Cardiopulm Rehab. 2002;22: 389-398.

16. Leon AS, Sanchez OA. Response of blood lipids to exercise training alone or combined with dietary intervention. Med Sci Sports Exerc. 2001;33(suppl):S502-S515.

17. Leon AS, Rice R, Mandel S, et al. Blood lipid response to 20 weeks of supervised exercise in a large biracial population: the HERITAGE Family Study. Metabolism. 2001;S513-S520.