Cholesterol and coronary heart disease

Cholesterol and coronary heart disease

Cholesterol & coronary heart disease get mentioned in the media quite a lot. Unfortunately, most of what you see & hear is either wrong or oversimplified to the point that it misses out what's actually happening. Fat and/or cholesterol doesn't stick to the insides of artery walls like grease on the inside of a drainpipe. This article sets about explaining what cholesterol is and what really happens to artery walls, and also tells you how to minimise your risk of getting a heart attack or stroke.

Cholesterol & coronary heart disease get mentioned in the media quite a lot. Unfortunately, most of what you see & hear is either wrong or oversimplified to the point that it misses out what's actually happening. Fat and/or cholesterol doesn't stick to the insides of artery walls like grease on the inside of a drainpipe. This article sets about explaining what cholesterol is and what really happens to artery walls, and also tells you how to minimise your risk of getting a heart attack or stroke.

What is cholesterol?

Cholesterol is a large, waxy molecule (C27H45OH) consisting of a hydrocarbon (fat-soluble) tail, a middle section consisting of four carbon rings (the steroid bit) and an alcohol (water-soluble) group on the end. Cholesterol is a powerful anti-oxidant and is what bile acids, mineralcorticoids, glucocorticoids, and sex hormones are made from.

Cholesterol is "chauffeured" around the body in lipoprotein "limousines". Lipoproteins are lipo (fat-soluble) at one end and protein (water-soluble) at the other end and form a spherical shell around their contents with the lipo end pointing inwards and the protein end pointing outwards. The shell is akin to the body of the limo. Inside the limo, there are apo(lipo)proteins which are akin to the driver, as they determine where the particles end up. The passengers are cholesterol, cholesteryl esters, phospholipids and triglycerides. These limos come in different variants, like chylomicrons, VLDL, LDL, IDL and HDL, the difference being the type and amount of apoprotein and the relative proportions of cholesterol and other ingredients, and there are sub-groups of each type also. Complicated, innit?

Cholesterol

The different variants are affected by how much triglycerides there are circulating in the blood. High serum triglycerides (caused by a chronic over-consumption of sugary & starchy carbohydrates for the activity level) result in cholesterol-depleted, triglyceride-rich particles and low serum triglycerides result in cholesterol-rich, triglyceride-depleted particles. Therein lies the problem. As cholesterol is a powerful anti-oxidant, small, dense (Type B) cholesterol-depleted particles are more prone to oxidation than large, buoyant (Type A) cholesterol-rich ones.

LDL that becomes oxidised is now bad LDL and is swallowed-up by scavenger macrophages. These then swell-up into foam cells which embed themselves into the intima of artery walls. Other processes also occur which cause cholesterol and calcium to build-up as a plaque in the media of artery walls. To see a cross-section through a typical artery wall, click here and scroll down to the bottom of the page.

This plaque build-up pushes the inner artery wall inwards making the artery narrower in cross-section, impeding the flow of blood through it. This can cause angina pectoris (pain in the chest) as the heart muscle is starved of oxygen. Eventually, especially if there are low levels of anti-inflammatories in the blood, the plaque can rupture, causing chunks of plaque to circulate and block-up narrow coronary arteries causing a heart attack, or narrow cerebral arteries causing a stroke. Unoxidised LDL is not bad and is not swallowed-up by scavenger macrophages.

It's possible to reduce serum triglycerides quite drastically by eating long-chain omega-3 fats from oily fish. These inhibit the conversion of glucose into triglycerides, but beware. Inhibiting the conversion of glucose into triglycerides can result in increased blood glucose levels (which is not good - see below) if sugary/starchy carb intake is too high. Solution? Reduce your sugary/starchy carb intake to suit your activity levels.

Why do foam cells embed themselves into the intima of artery walls?

Arteries are muscular tubes. They open & constrict to control the flow of blood through them. When you get cold, they constrict to reduce the flow of blood to the skin to prevent excessive heat loss. When you get hot, they open to increase the flow of blood to the skin to increase heat loss.

Foam cells don't go just anywhere. They embed themselves into damaged areas of artery walls. This is a good thing otherwise damaged artery walls could rupture, causing a haemorrhage.

What damages artery walls?

  • Chronically-high blood pressure.
  • Chronically-high blood glucose.
  • Chronically-high blood free radicals.
  • Chronically-high blood homocysteine.
  • Chronically-low blood anti-oxidants.
  • Chronically-high blood pro-oxidants.
  • Chronically-low blood anti-inflammatories.

How can I reduce damage to artery walls?

  1. Have blood pressure (BP) tested regularly. There's one problem with having your BP taken in a GP's surgery and that is 'white-coat hypertension' where the stress of having your arm squeezed by the cuff sends your BP up! If you buy your own BP monitor (Lloyds pharmacy sell a fully automatic BP monitor with standard cuff for £9.99), you can become accustomed to using it and overcome white-coat hypertension.
  2. Have blood glucose (BG) tested regularly. If you're lucky, you may be able to request a HbA1c test. This shows accumulated damage to red blood cells by blood glucose.
  3. Don't smoke! Apart from lung cancer, chronic obstructive pulmonary disease & emphysema, smoking is the No.1 best way to damage your arteries and get them clogged-up.
  4. Take a good B-complex tablet each day containing B6, B12 & Folic acid, which lowers homocysteine levels.
  5. Ensure that your diet is high in natural anti-oxidants from coloured veggies (beta-carotene), fruits (Vitamin C + bioflavonoids), tomatoes (lycopene), sesame seeds (gamma-tocopherol), Brazil nuts (selenium), alcohol and/or red wine in moderation, green tea in moderation, extra-bitter chocolate in moderation, onions/garlic etc.
  6. In men and non-menstruating women, excess iron in the blood is pro-oxidant, so don't supplement with iron. Menstruating women have the opposite problem, so they should supplement with iron.
  7. Take about 2g/day of long-chain omega-3 fats, or about 20g/day of flaxseed oil if male, or about 10g/day of flaxseed oil if female.

What about Benecol & Flora Pro-Activ?

These yoghurts & spreads contain plant sterols or stanols, which reduce total serum cholesterol by up to 15%. However, as explained above, it's LDL quality that counts, not quantity, and there is no evidence to show that these foods actually save any lives.

What about statins?

Statins (HydroxyMethylGlutarate Coenzyme-A Reductase inhibitors) reduce total serum cholesterol. They also have anti-inflammatory and anti-clotting effects by reducing levels of the non-sterol derivative mevalonate and its subsequent products. Click here to see the cholesterol synthesis pathway. Statins do save lives in people who have already had a heart attack and also in men between the ages of 30 and 60. However, younger or older men and all women do not get reduced number of deaths, though heart-attack deaths may be slightly lower. I would strongly recommend anyone who is taking statins to supplement with 100mg/day of Coenzyme-Q10, as the synthesis of this vital substance is suppressed by them. Note that omega-3 fats also have anti-inflammatory and anti-clotting effects as well as anti-arrhythmia effects and don't suppress the production of Co-Q10.

What about eating cholesterol?

As cholesterol is eaten, the liver secretes less to compensate. As an average egg contains about 250mg of cholesterol, you can eat two eggs per day (500mg of cholesterol per day) without significantly affecting cholesterol levels in the blood. Click here to learn more.

Nigel Kinbrum

Evidence-Based Diet, Nutrition & Fitness Information, and Random stuff.



More from Diet


Top