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“Live healthy...Live well”

Dedicated to providing pertinent information on health, fitness, and nutrition to foster a culture of wellness among Southwest Airlines flight crews and their families.

by Larry Kline

email: livehealthy-livewell@cox.net

YOU’RE ONLY AS OLD AS YOUR ARTERIES – as we age, the aorta, carotids, and other large arteries that keep oxygen-rich blood flowing through the body lose some of their capacity to widen or narrow – they become less compliant.

With aging, arterial compliance declines and arterial stiffness increases. Arteries are most supple at about age 30 and then start stiffening. Factors that contribute to this declining function include:

Rigid walls. The two main structural proteins in the large artery walls are collagen and elastin. Collagen provides the “scaffolding” that holds the arteries together, and elastin gives the blood vessels the elasticity that they need to manage the flow of blood.

As people get older, collagen becomes more abundant in artery walls. Over time, strands of collagen tend to bind (cross link) with other collagen strands. Both combine to make the large arteries more rigid. If there is extra glucose (blood sugar) in the blood, cross-linking increases as the glucose binds to the collagen to form advanced glycation end-products, or AGEs. As the years go by, the elastin proteins stretch out and eventually start to rupture. That makes the arteries lose even more flexibility.

Damaged linings. Not only do the walls of the arteries get stiffer as they age, the arterial lining also gets stiffer. The endothelium is the inner lining of cells in all of the arteries in the body. It regulates where blood flows and how much blood flows to the organs as needed, and it maintains the blood in a fluid state so that it does not clot.

Endothelial cells produce nitric oxide, a gas that relaxes and dilates blood vessels. An impaired lining produces less nitric oxide, which leads to less flexible arteries. Nitric oxide not only relaxes and dilates blood vessels, but also prevents platelets and white blood cells from sticking to blood vessel walls. Less nitric oxide leads to more plaque buildup in artery walls, which means that the lining produces even less nitric oxide, which leads to more plaque buildup in artery walls – a cycle that increases cardiovascular risk in people.

Age is a major factor in this decline. All other risk factors that are known to lead to coronary heart disease also have been shown to hinder endothelial function. High blood pressure, cigarette smoking, diabetes, high cholesterol, being overweight, or not doing enough exercise all contribute to arterial decline. If the endothelium is abnormal, it means that the cumulative load of risk factors and lifestyle has led to damage to the arteries which greatly increases the risk of developing heart disease or heart failure, heart attack, or stroke.

The endothelium is a “barometer” of the health of the blood vessels because it is one of the first things to go wrong on the path to atherosclerosis, which is the underlying cause of heart attack and the most common form of stroke.

LDL cholesterol inside the artery walls is generally removed by HDL particles. If the HDL cannot keep up, the LDL causes the arteries to narrow and stiffen. As the excess cholesterol builds up, white blood cells enter the artery wall to remove these “invaders.” But excess LDL can engorge the white blood cells and turn them into foam cells, triggering inflammation, causing more repair cells to enter the artery wall, creating more plaque. A cap forms over damaged artery walls. If the cap ruptures, the plaque may ooze out and trigger the formation of a blood clot which could block the artery resulting in a heart attack or stroke.

THE CONSEQUENCES

Scientists are learning that stiffening arteries can often be detected (in the research laboratory) long before any symptoms of disease appear, and that can predict who will develop cardiovascular disease. Risk factors include:

High blood pressure. If your arteries are stiff, the heart has to work harder to pump blood. Nine out of ten people will develop high blood pressure if they live long enough. Most of this is systolic hypertension that is directly due to arterial stiffening. (Systolic pressure is the maximum pressure on the arteries when the heart contracts and pushes blood out – it is the top number in a blood pressure reading).

It is now recognized that increased systolic blood pressure with age is really the blood pressure change that is linked mostly to premature death in adults over 50. When arteries are stiff, blood pumped from the heart moves so quickly through them to the extremities that the pulse wave that is generated bounces back to the heart while the heart is still contracting which adds to systolic pressure.

Heart attacks and strokes. Arterial stiffness is as powerful a predictor of future cardiovascular disease risk in older adults as LDL cholesterol or any of the major conventional risk factors. Meta-analysis pooled the results of 17 international studies that tracked nearly 16,000 people for an average of eight years. Those who entered the studies with the stiffest arteries but without signs of heart disease were twice as likely to later die from a heart attack or stroke as those who entered the studies with the most supple arteries.

Cognitive decline. If the arteries cannot expand and contract easily, they cannot shield the smaller blood vessels from the regular high-pressure bursts of blood that leave the heart. These pressure spikes may damage the brain.

Several studies on aging have shown that those with stiffer arteries were more likely to show declines in verbal learning skills and memory over the next decade than those who started out with less-stiff arteries.

HOW CAN YOU TELL?

It is not possible to take a sample of the arterial wall in a study of living people, so samples have been taken during autopsies and these results have been compared and analyzed. For indirect measurements of arterial stiffness, a patient lies down while electrodes are placed on the skin along two arteries. Data is recorded on how fast it takes for a pulse to travel between two points (pulse wave velocity). The greater the velocity - the stiffer the artery. Since stiff arteries cannot expand well, they pinch the blood flow and send it shooting through at a faster speed.

Endothelial function is typically measured with something called flow-mediated dilation, which uses ultrasound to see how wide an artery opens after being deprived of blood with a cuff that is tightened on the arm. If people have impaired endothelial function, their arteries won’t widen as much during the test.

WHAT YOU CAN DO

Regular aerobic exercise may have the greatest effect on arterial stiffness. If you compare older adults who do regular aerobic exercise with older sedentary adults, those who exercise regularly have more-compliant arteries and less stiffening. Using pulse wave technology, scientists have found that the arterial stiffness in exercisers (the youngest being 54) was no different than the arteries of sedentary people aged 20 to 44.

During exercise, the physical force of blood accelerates through the arteries causing the endothelial cells to release nitric oxide. This has beneficial effects on the wall of the artery that results in an anti-stiffness effect. Studies in older test subjects who have stiff large arteries show that daily walking can lead to a 25 percent improvement in arterial stiffening within three months. The beneficial effects last as long as the person continues daily exercise.

Exercise can also help improve endothelial function in sedentary adults. Again, test subjects who exercised daily for three months realized about a 30 percent improvement, comparable to that of people their own age who ran regularly. These improvements in arterial health were achieved with moderate-intensity walking that can be safely performed by most if not all sedentary healthy adults.

Strength-training can actually increase arterial stiffening, due to the increased blood pressure that occurs temporarily. Many physicians recommend combining strength training with aerobic exercise. Older adults need to incorporate resistance-training to their exercise session for muscle preservation. The combination of aerobic training and strength training can maintain muscle mass and arterial flexibility. A 2006 Japanese study showed the arterial compliance of people who did resistance training for four months declined by 20 percent, while the arterial compliance of those who combined aerobics with resistance training did not change.

Diet: The following factors affect arterial health:

SODIUM. The component of the diet with the most evidence for slowing arterial stiffening is sodium. Sodium restriction has a very powerful effect on the arteries. Cutting the average sodium intake of U.S. adults in half results in a 25 to 30 percent improvement in the stiffness of the arteries in just one week. One study had adults in their 60s who had systolic hypertension (148/84) slash daily sodium intake from 3,100 milligrams a day to 1,300 mg/day. Carotid artery compliance increased by 27 percent after one week and by 46 percent after two weeks

SATURATED FAT. Endothelial function drops quickly after a fatty meal. Within three hours of consuming a meal heavy with saturated fats, endothelial function can decrease by half compared to those consuming a similar meal without the saturated fats, and the arteries look similar to the arteries of a person who has heart disease.

Saturated fat and trans-fat are the worst for arteries. Polyunsaturated fats seem to be much less damaging and monounsaturated fats like those found in olive oil seem to be healthful.

VEGETABLES. A study from the United Kingdom showed that after two months of people eating various amounts of daily fruits and vegetables those who ate the most fruits and vegetables had the best endothelial function – function improved by 6 percent for each daily serving of a vegetable or fruit consumed.

POTASSIUM. Consuming potassium in a supplement (2,500 mg/day) for four weeks improved endothelial function and arterial compliance in test subjects with mild hypertension, compared with those who took a placebo. The best source of potassium is fruits and vegetables.

FISH OIL. The omega-3 fats in fish oil can improve endothelial function. People with high cholesterol (average 255) given daily fish oil capsules improved their arterial compliance by almost 40 percent compared to those who consumed a placebo.

Weight. Weight gain is associated with increases in pulse wave velocity. Weight gain and obesity is considered a form of accelerated aging with regard to the blood vessels. Losing weight improves arterial compliance.

THE BOTTOM LINE

For optimal cardiovascular health, get regular exercise, cut back on sodium, saturated and trans-fats, eat a diet heavy with fruits and vegetables, eat two servings of seafood a week and maintain a healthy weight. Nutrition Action Healthletter 10/2010, Men’s Health 9/10.