Zinc protects against heart disease

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Summary:

Study done at National University of Singapore shows zinc

supplementation in animals reduces CVD. Zinc does not lower blood

cholesterol levels, but reduced aortic lesions by 66 per cent in

rabbits, by possibly influencing iron metabolism.

Link and full text:

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Zinc supplements could protect against CVD

05/06/2006- Zinc supplements may decrease the risk of heart disease,

says an animal study from Singapore, results that appear to support

previous benefits afforded by the mineral.

Atherosclerosis is the process whereby fatty substances such as

cholesterol and calcium form plaque on the inner lining of an artery,

causing them to harden. If enough builds up the plaque can reduce

blood flow through the artery, and if it ruptures blood clots can

form, which can block the flow of blood to the heart and cause a heart

attack.

Atherosclerosis occurs naturally in humans as part of the aging

process, but certain factors including high blood cholesterol,

smoking, high blood pressure, obesity and diabetes increase the risk.

A report last year in the Journal of Nutrition (Vol. 135, pp.

2114-2118) reported that deficiency in zinc in mice was associated

with an increase in the risk of cardiovascular disease (CVD) through

inflammation and a decreased level of compounds that protect against

atherosclerosis.

The new research, published on-line in the journal Free Radical

Biology and Medicine (doi: 10.1016/j.freeradbiomed.2006.03.017),

reports that supplementation of a high cholesterol diet with zinc

reduced the formation of lesions in the arteries of rabbits, but the

effects were not linked to changes in cholesterol levels.

Lead researcher Barry Halliwell and colleagues from the National

University of Singapore divided 18 white rabbits into three groups.

The first was fed a normal diet (control), the second fed a

high-cholesterol diet (HCD, one per cent cholesterol), and the third

was fed the HCD diet but was supplemented with zinc in the carbonate

form (0.1 per cent).

After eight weeks, the researchers measured blood levels of HDL, LDL,

and total cholesterol, as well as triglyceride levels. The number of

white and red blood cells were also measured.

The researchers found that zinc supplementation did not significantly

change total cholesterol, LDL, or triglyceride levels, but a

significant decrease in HDL levels was observed – 6.9 millimoles per

litre in the HCD group and 2.6 millimoles per litre in the HCD plus

zinc group.

This result appears to agree with last years report that zinc

deficiency is associated with increased levels of HDL.

" Since HDL is antiatherosclerotic, it seems unlikely that the

protective effects of zinc are mediated by altering plasma lipid

levels, " wrote lead author Minquin Ren.

When the scientists investigated the formation of lesions in the

rabbit aorta. They found that zinc supplementation significantly

decreased the area of the lesions by 66 per cent, a result linked to a

decrease in iron concentrations in the tissue, which has previously

been reported to catalytically promote damaging free-radical reactions

and the development of atherosclerosis.

" Other evidence that zinc is influencing iron metabolism is that the

red blood cell dropped in the HCD animals from 5.9 to 3.04bn per

litre, whereas in the Zn-supplemented HCD animals the drop was

smaller, from 5.9 to 4.07bn per litre, " said Ren.

" Zinc may thus play a role in inhibiting lesion formation through the

indirect prevention of iron-mediated free-radical damage, in that it

decreases the iron content of the lesion, " concluded the researchers.

Research is reported to be on-going to determine the mechanism behind

the reported benefits.