Coronary Artery Calcium

The Coronary Artery Calcium (CAC) test is a relatively new radiographic procedure that is used to evaluate how much calcium is deposited in the walls of the arteries that supply the heart. Such calcification is a sign of long-standing cardiovascular disease and is an indicator of increased risk of heart attacks and strokes.

But although it does have clinical significance for pretty much anyone, it becomes a lot less important in people over 50, at least in and of itself. Even substantial calcification in older people has to be considered in relation to the overall amount of atherosclerosis and blood vessel stenosis (narrowing). Those over 50 may have calcification without major stenosis, and it’s actually a common thing to find in aging blood vessels.

In fact, calcified plaques in the blood vessels are generally more stable than cholesterol-based plaques, which can increase in size relatively quickly, and/or break free from the walls of blood vessels and create sudden circulation problems when they lodge in smaller vessels, such as in the heart, lungs, and brain. So, elevated CAC by itself is not a particularly concerning finding in people in their 50’s or older.

High CAC in younger people; however, is a more worrisome condition. It is a sign that the blood vessels are aging more rapidly than normal and indicates a more significantly elevated risk of cardiovascular health issues.

As with any cardiovascular risk, things like exercise and diet modifications are recommended for minimizing progression or even reversing the narrowing of the blood vessels. But unlike atherosclerosis that’s due mostly to cholesterol and fatty substances adhering to the interior of vessel walls, calcification tends to be actually in the smooth muscle that composes the blood vessel itself.

The calcification also does not usually appear to be due to an excess consumption of calcium. So what does cause it?

Well, the answer to that is still somewhat uncertain, but there is some new information from rodent studies that might shed some light on the situation. It appears that a deficiency of potassium stimulates the smooth muscle cells of the blood vessels to take up calcium.

The theory as to why this happens has to do with “undifferentiated” cells – also known as stem cells. These cells are able to develop into more specialized cells depending on the body’s needs. It is thought that when the normal balance between calcium levels and potassium levels in the blood is shifted towards higher calcium over an extended period of time, the undifferentiated cells in the blood vessels develop more like bone cells than the normal smooth muscle cells in order to pull the calcium out and restore the balance.

Older individuals would generally have more potential for the imbalance between calcium and potassium and the consequent shift in cell function to occur, therefore some calcification of the blood vessels is relatively common. But when this is occurring in younger individuals, it is a warning sign that the problem is more severe and the blood vessels are changing at an accelerated rate beyond normal aging.

In any event, low potassium levels are pretty common in populations that consume a lot of processed foods and low amounts of fresh vegetables, fruits, and cold water fish like salmon and tuna. Americans have been found to get on average about half the recommended intake of 3500 – 4000 mg of potassium per day.

Because consuming excess potassium carries risks of its own, the FDA limits the amount of potassium that can be in supplements. The risk of overdosing on potassium is quite low for most individuals as it would require a huge number of supplement pills or eating massive quantities of fruits and vegetables to reach a toxic dose. In any event, increasing potassium intake is actually easier to achieve through food than through supplements because of the dosage limits.

Although bananas are the “classic” potassium food, a wide variety of fruits and vegetables contain significant amounts. If you’re eating a reasonably good diet, it’s not that difficult to reach the recommended intake of 3500 – 4000 mg per day. But a lot of people don’t eat a reasonably good diet, and if you rarely eat vegetables and/or fruits, you might want to consider making some dietary changes – and not just to get more potassium, although that is beginning to appear to be quite important!

Until next time…

George F. Best, D.C.