Yes, high levels of cholesterol in the blood increase the risk of heart disease. Yet some people manage to elude heart attacks even when their numbers are high. It could be that the way your body oxidises cholesterol in the blood may point to susceptibility to heart disease.

At the University of Southern California in Los Angeles, Dr Alex Sevanian said “your predisposition to atherosclerosis may depend much more on how much cholesterol oxide your body happens to produce than on the cholesterol levels in your blood”. Ironically, the LDL carrier of cholesterol oxidises more rapidly in the presence of polyunsaturated fats as found in corn and soybean oils. (That’s another reason to start emphasising monounsaturated rather than polyunsaturates in your diet.) So far, Dr Sevanian’s work has been on laboratory animals, but human studies are scheduled in a number of lipid research centres.

At a meeting of the American College of Cardiology in 1989, Dr Thomas Carew of the University of California at San Diego said LDL, the bad cholesterol, may exert its deleterious influence only after it is oxidised and can then be taken up by scavenger cells known as macrophages. When the macrophages become laden with oxidised LDL, they imbed themselves in arterial walls, where they are transformed into foam cells, the first stage in the development of atherosclerosis.

What can one do about cholesterol oxidation? We have preliminary evidence that one can, indeed, limit this destructive process.

Dr Carew, working with noted lipid researcher Dr Daniel Steinberg in San Diego, found that the prescription drug probucol (Lorelco) limits cholesterol oxidation. Probucol has been prescribed for cholesterol reduction, but its use has been limited by the fact that it reduces the good HDL as well as LDL levels.

Working with another eminent lipid researcher, Dr David Blankenhorn, of the University of Southern California, Dr Sevanian has found that a non-drug approach may achieve the same results. He has shown that blood levels of cholesterol oxides can be reduced with vitamin E, which has long been known to be a potent anti-oxidant.

A report of Canadian researchers at the 1990 meeting of the American Heart Association showed the value of vitamin E in protecting patients from adverse effects of bypass surgery. A group of 14 patients received 300 mg of vitamin E daily, while another group of 14 got a placebo for two weeks prior to their operations. Those getting the vitamin E suffered less “metabolic dysfunction” during the procedure.

Scientists at the University of Toronto have been looking for ways to protect bypass patients from the decrease in heart function that occurs after they are taken off the heart-lung machine which keeps blood circulating and oxygenated during surgery. They have found that unstable molecules known as free radicals may be a major factor in the heart’s inability to resume normal metabolic activity after the operation. In addition, surgery depletes the amount of vitamin E normally in the bloodstream.

Dr Terrence Yau said that presurgical supplementation with vitamin E apparently improved the heart’s ability to function, especially during the dangerous five-hour period immediately following the operation.

Much of the initial research into the activities of free radicals has been done in Japan, and scientists there continue to investigate this important area. Now researchers report that free radical-induced oxidation of LDL cholesterol can be suppressed by supplementation with vitamins E and C. They conclude that vitamin C inhibits water-soluble radicals but could not scavenge fat-soluble radicals within LDL, while vitamin E scavenged fat-soluble radicals in order to break the chain reaction of LDL oxidation.

All the researchers involved in such studies point out the need for additional study, and state that they do not currently advocate self-supplementation. However, in private they admit that they themselves take anti-oxidants regularly. Moreover, the doses of supplements used is not excessive, and while the absolute evidence of benefit has not yet been delivered, the risk of taking reasonable doses of those vitamins is virtually absent.

And while we’re on the topic of nutrient supplementation, add chromium to the list. When subjects were given a 200-microgram dose, their cholesterol levels fell by seven per cent. The recommended “safe and adequate” intake for the trace mineral is 50 to 200 micrograms daily; it’s found in oysters, brewer’s yeast and beer as well as in the organ meats which are on the no-no list for those of us cutting dietary cholesterol. A 1991 study showed that 90 per cent of Americans consume less than 50 meg. Daily intake of chromium should be no more than 200 meg, however, since higher levels can lead to adverse reactions including skin rashes, mood changes and anaemia. Take a look at your vitamin/mineral supplement’s formulation to see how much chromium is included. A dosage of between 50 and 200 meg may do some good and won’t do any harm.

Beta-carotene, the precursor of Vitamin A, has also been shown to have advantages in heart disease. A study of beta-carotene was reported at the 1990 meeting of the American Heart Association in Dallas. Of 333 patients with documented coronary heart disease, those taking a beta-carotene tablet every other day suffered half as many cardiovascular events as those getting a placebo.

Charles H. Hennekens, MD, of Brigham and Women’s Hospital and Harvard Medical School, said the data provide the first evidence in humans of the potential efficacy of beta-carotene in protecting the arteries. His research, known at the Physicians’ Health Study, is a national project involving about 22,000 male physicians aged 40 to 84.

The 333 individuals in the beta-carotene study are those physicians who had evidence of cardiovascular disease when they entered the project. In those taking the beta-carotene, there were half the number of strokes, heart attacks, sudden cardiac deaths and bypass surgeries.

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Cardio & Blood/ Cholesterol