The Aging Process

Bones are deceptive: From the outside, they appear hard and stagnant. But bones are bustling with activity. Their tough exterior conceals a vast network of blood vessels that transport nutrients to, and wastes away from, working bone cells. Bones are constantly being remodeled; they are in a continuous cycle of destruction and renewal until the day you die.

The problem is, as time passes you lose more bone than you make. As a result, bones thin and become increasingly susceptible to fracture. As this process accelerates after age 50, osteoporosis becomes more common. Osteoporosis is a condition of progressive bone loss that is painful, disfiguring, and debilitating.

It weakens bones to the point that fracture comes easily. Even coughing, tugging on a cabinet door, and especially a fall, can cause a fracture in those who suffer from advanced osteoporosis. Some bone loss with age is unavoidable, but the rate at which bone is lost is highly individual.

Genetics plays a role in the development of osteoporosis -- Caucasian and Asian women are more likely to develop osteoporosis, as are those who have relatives with the disease. Menopause is also a culprit: Bone loss accelerates in the five years or so after menopause.

Bad habits, such as smoking and excessive use of alcohol, also contribute to bone loss, as does a sedentary lifestyle and inadequate intake of calcium and vitamin D. Certain medications such as cortisone-like drugs and cholestyramine, a drug to lower blood cholesterol levels, also accelerate bone loss. So do some medical conditions such as rheumatoid arthritis.

However, much research proves that regularly performing weight-bearing exercise, such as walking and lifting weights, and getting an adequate amount of calcium and vitamin D can keep bones strong longer, building bone and reducing the risk of osteoporosis, even in the elderly

If you think you're getting shorter, you're probably right. Everyone shrinks with age. We're tallest by the end of our forties, then lose up to two inches in height by age 80. The loss in height is gradual but accelerates late in life. Why do we get shorter with age? There are myriad reasons including weaker muscles; water loss; postural changes; and deterioration of the spongy disks separating the vertebrae in our backbone, causing a compression of the spine.

Women tend to lose more height than men because they are more often the victims of osteoporosis, which results in loss of bone tissue in the vertebrae of the backbone, compressing it and making you shorter. That's why it's so important to maintain bone health and strength throughout life. And it doesn't hurt to sit up straight, either.

Joints become less resistant to wear and tear with time. That's in part because of the changes in cartilage, the tissue that cushions the tips of the bones in your joints. Aging causes cartilage to lose water, making it more vulnerable to injury from repetitive motion and stress. Arthritis is characterized by pain and stiffness in the joints, and in some forms, swelling, redness, and heat.

It is more common with each passing decade. Osteoarthritis, the most common form of arthritis, occurs when cartilage begins to fray and decay. Osteoarthritis is usually confined to hips, knees, spine, and hands.

Carrying around excessive weight aggravates osteoarthritis in the knees and hips, which bear weight. In fact, being overweight increases your risk of developing osteoarthritis. Regular physical activity may help reduce joint pain and stiffness and increase flexibility, muscle strength, and endurance.

You may have noticed that you can't lift heavy loads nearly as well as you could five or ten years ago. That's because aging causes a decrease in the strength, size, and endurance of muscle tissue, perhaps due in part to decreased blood flow to muscle tissue. But don't put less strength and tone down to age: Inactivity wreaks much more havoc on muscles than time does.

Sitting around accelerates muscle loss. In fact, experts say the loss in strength and stamina that we take for granted with old age is in part caused by reduced physical activity. By age 75, one in three men and half of all women get no regular exercise, which exacerbates the muscle loss that age causes.

Skin is composed of two main layers: the epidermis, the layer you wash and dry, and the dermis, which lies directly below its more visible counterpart and is where hair and sweat glands originate. Dermal and epidermal cells diminish in aging. The dermis actually thins by about 20 percent, and the blood supply to it drops off with time. Wrinkles develop, primarily due to a loss of collagen, a cementlike protein that holds cells together.

When it goes, so goes elasticity, the property that provides skin with its resilience, helping you avoid laugh lines and crow's feet in your youth. Sun exposure, too, is a major contributor to the development of wrinkles. In fact, the sun causes most skin damage, including brown "age spots" and skin cancers.

As skin gets thinner and less elastic, it becomes more fragile, bruising and tearing more easily and taking longer to heal. The loss of some sweat and oil glands from the dermis may result in chronically dry skin. Thinning skin also compromises its ability to act as a barrier to infection. Skin injuries, more common with age, also increase your vulnerability to infection.

Aesthetics aside, thinning skin has implications for your health. Your skin participates in the body's vitamin D production. Vitamin D is calcium's partner in helping keep bones strong. It gets its start in skin that's been exposed to strong ultraviolet light.

Since aging skin has a limited capacity to initiate vitamin D production, vitamin D deficiency is more common in older people, especially those living in northern climates, where the sun is too weak to make vitamin D for half the year. Applying a sunscreen with a Sun Protection Factor (SPF) of 8 or higher helps protect your skin but blocks much-needed ultraviolet rays.

In the next section, learn about the cardiovascular effects of aging and how to manage them.

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Aging brings on increased stiffness of the chest wall, diminished blood flow through the lungs, and a reduction in the strength of your heartbeat. (In fact, maximum heart rate per minute declines with each year and can be estimated by subtracting your age from 220.) Don't worry too much about this, though. Your heart pumps more blood per beat to compensate for a diminishing heart rate.

Older people take longer to recover from stress, a shock, or surprise. After exertion, such as exercise, more time passes before your body returns to its resting heart rate and blood pressure. Older people often feel colder than their younger counterparts, largely due to diminished circulation. Blood vessels change, too. Artery walls slowly thicken and become less elastic, increasing their vulnerability to normal wear and tear.

While arterial thickening is considered normal, it may predispose you to the buildup of plaque inside your arteries. Plaque restricts the flow of blood to the heart and the brain, which can lead to heart attack or stroke.

Plaque buildup increases with age but is exacerbated by elevated total cholesterol levels and by elevated LDL (low density lipoproteins, the "bad" cholesterol) levels in the blood. A diet rich in saturated fat and cholesterol and low in fiber coupled with a sedentary lifestyle contribute to high blood levels of total cholesterol and LDL cholesterol.

Until about age 50, men have higher blood cholesterol concentrations than women. That's thought to be the result of the protective function of estrogen, a female hormone that helps keep blood cholesterol levels in check. Even when estrogen levels fall and blood cholesterol levels rise after menopause, women still run a lower risk of heart attack and stroke from clogged arteries than their male peers.

Because they haven't been suffering from the same damaging high cholesterol levels as men, women suffer from heart attack and stroke an average of ten years later in life than men. But once menopause starts, a woman's risk for heart attack and stroke rises steadily with each passing year. Between 40 and 50 percent of people over the age of 65 have high blood pressure, yet scientists are not sure why.

In about 95 percent of the cases the cause remains a mystery. The decreased elasticity of the blood vessels as we age may be at least partially responsible for high blood pressure, but lifestyle may be equally, if not more, responsible. Studies show that less technologically advanced countries have virtually no high blood pressure with advancing age, while industrialized nations such as the United States show a steady increase.

Why does it matter? Elevated blood pressure harms blood vessels. You may feel fine, but out-of-control blood pressure is an insidious condition that puts you at greater risk for stroke, heart disease, kidney failure, and other ailments.

Continue to the next page to read about the gastronomical effects of aging.

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You may not think of your mouth as being part of the gastrointestinal system, but in fact, it's the very starting point of the process by which you digest foods and absorb nutrients. As you age, chewing can become more difficult, you may chew more slowly, and you may not chew your food as efficiently. That's especially true if you have dentures or poor dentition.

Chewing is important, though, because it breaks down food so that stomach acid and intestinal enzymes can better attack it, digesting it to its smallest components to be absorbed by the intestine. When you swallow larger pieces of food, it takes about 50 to 100 percent longer for it to make its way to your stomach because your esophagus, the pipe that connects your mouth with your stomach, doesn't contract as forcefully as it did when you were younger.

As a result, you are also more vulnerable to choking. Slowing down and chewing food thoroughly will help you make the most out of your eating experience and help eliminate some of the problems caused by gulping larger chunks of food. As many as 30 percent of Americans over the age of 60 do not produce enough stomach acid because of two conditions: hypotrophic gastritis (reduced production of stomach acid) or atrophic gastritis (the absence of stomach acid).

You may not feel either of these conditions, but their effects are real. Too little stomach acid results in faulty vitamin B12 absorption. A deficiency of vitamin B12 in your bloodstream and tissues can lead to pernicious anemia and irreversible nervous-system impairment and may contribute to high levels of homocysteine in your blood. High homocysteine is one of the risk factors for heart disease.

People over age 60 have a greater risk of developing gallstones, perhaps because of the narrowing of the bile duct at the opening of the intestine. A high fat diet also puts you at greater risk. When you digest fat you need bile, a substance made by the liver and stored in the gallbladder. Gallstones form when liquid stored in the gallbladder hardens into rock-hard material.

As you get older, you produce less lactase, the digestive enzyme that breaks down the carbohydrate in dairy products known as lactose. It's difficult to pinpoint how many older people can't tolerate the likes of milk, cheese, and ice cream. But if you have bloating and discomfort beginning within hours of eating dairy products, you probably have some diminished tolerance for lactose.

Lactose intolerance is individual. That's why you may be able to tolerate some dairy products and not others. For example, many people with lactose intolerance can eat yogurt, which is lower in lactose than a glass of milk. In addition, consuming milk or other dairy products with food helps to decrease the effects of lactose intolerance, as does consuming smaller amounts at a time.

As you get older, your gut -- particularly your colon -- may become sluggish and less toned. One in three people age 60 or older have diverticula, which are outpouchings in the lining of the large intestine. These pouches are the result of increased pressure within the intestine caused by decreased muscle tone. In addition, when your gut gets sluggish, you become more vulnerable to constipation.

Your liver is your largest internal organ, weighing in at about three pounds. But it gets smaller with time, beginning around age 50. The liver's shrinkage begins at the same time that body weight and muscle mass start their decline. However, in the very old, the liver becomes disproportionately small. Having less liver tissue and decreased blood flow to this organ means that your body may handle certain medications differently.

That's why the older you get, the more often you and your doctor should evaluate the effect of all of the medications you take and discuss your alcohol intake.

You can't live without it, but you probably know little about why your liver is so important. The liver:

With time, you may become infected with Helicobacter pylori (H. pylori) -- a pesky bacteria that hitches a ride on the stomach lining and is the cause of nearly all ulcers. Ulcers are sores or holes in the lining of the stomach or duodenum, a part of the small intestine. They cause pain when the stomach is empty, such as between meals and in the wee hours of the morning, but irritation can come at any time.

Sometimes the pain lasts for minutes; other times it hangs around for hours. Eating or taking antacids may relieve your distress, but only temporarily. H. Pylori infects about 60 percent of American adults by age 60, but infection with the bacterium does not necessarily mean you will develop an ulcer.

However, the presence of H. Pylori does increase your chances because it weakens the protective mucous coating in the digestive tract and makes it vulnerable to the corrosive effects of stomach acid. H. pylori infection is easily cured with antibiotics, sometimes in combination with acid-suppressing medication to alleviate the symptoms and heal the ulcer.

How will you know if H. pylori is plaguing you? Your health care provider can use any of the following tests to diagnose H. pylori infection:

You've got two of them, and boy, are they a busy pair. All the blood in your body is constantly filtered by the kidneys, which determine the elements to keep and those to eliminate in urine. Without adequate kidney function, you would not be able to clear toxic byproducts of normal metabolism or those of medication breakdown.

Nor would you be able to regulate water balance and blood pressure. Functioning kidneys actually participate in bone health, too, by finishing off vitamin D production that begins in the skin and by regulating calcium and phosphorus loss in urine.

When you're born, each kidney tips the scale at a shade more than 1.5 ounces. As you grow, so do they -- to about nine ounces a piece. But as you age, they begin to decrease in size. By your eighties, they've shrunk to about six ounces each. Kidneys also gradually become less efficient at filtering your blood and making urine, beginning around age 30. And as you get on, less blood makes it to the kidneys.

While scientists agree that kidney function drops off with age, they can't agree on why. It could be that you lose nephrons, or kidney cells, and this decreases the organs' capabilities. Some say that undetected infection, injury, and medication reactions and a decrease in blood flow caused by vascular disease may be the reason that kidney function flounders.

Whatever the cause, you can preserve kidney function by drinking plenty of fluids; controlling cardiovascular disease, including high blood pressure, as much as possible; and keeping blood glucose levels in check, especially if you have been diagnosed with diabetes. Chronically high blood glucose destroys the tiny blood vessels that supply the kidneys, causing cell damage and death.

Now that you've digested a hearty amount of information about the gastronomical effects of aging, it's time to learn about the immunological effects of aging. Continue to the next page to find out more.

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The immune system is nothing short of a massive army at the ready, defending the body 24 hours a day. A sophisticated network of cells and organs stationed around the body protects you from invaders such as bacteria, viruses, fungi, and parasites.

This network produces and houses the materials to fend off any threat to good health, including the cell production gone haywire that can evolve into a cancerous tumor. What the immune system can't repel, it seeks out and destroys.

If the immune system is an army, white blood cells are the enlisted men. White blood cells and the antibodies they produce are the workhorses of the immune system. They make their rounds via your bloodstream. When invaders enter the body, or when mutant cells are formed, your body mounts its defense by generating a specific antibody.

Antibodies are produced by white cells residing in your spleen and in your lymph nodes. An antibody can finish off germs or bad cells, or it can earmark them for destruction by a type of white cells called macrophages, which are responsible for engulfing and destroying unwanted cells.

Aging decreases immunity by impairing the body's production of antibodies. Fewer antibodies means a more sluggish immune system that's less responsive to foreign elements and to potential cancer cells.

There's a little-talked-about organ that scientists say may be the key to preserving immune function. It's the thymus gland, and unfortunately, it takes a hit with advancing age. When you're born, the thymus gland weighs up to about half a pound, but it shrinks to a fraction of an ounce by age 60. In short, it virtually disappears.

But we may need the thymus gland to help prevent our immune system from deteriorating. The thymus gland produces hormones that may be responsible for keeping our immune system intact, as well as stimulating and controlling the production of neurotransmitters, which are chemical messengers that serve as the go-betweens among nerve cells.

Time also brings with it subtle body changes that may confuse your immune system. That confusion results in the body's production of antibodies against itself, since it believes its own cells to be a threat to your well-being. In essence, aging increases the chances that the body will turn against itself and destroy its own tissues. Autoimmune diseases such as rheumatoid arthritis or lupus may be the result.

In the next section, learn about how aging effects the metabolic process and your mental health.

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As you get older, it's normal to gain weight, right? It may be normal -- if you define "normal" as "common" -- but it's not desirable, and it's not inevitable either. Chances are, you weigh more now than you did ten years ago. Or maybe your waistline has expanded, but the scale's remained steady.

Understanding what happens with weight as your body ages will help you to control it. Beginning around age 25, total body fat starts to increase, while muscle mass and body water decrease. As a result, you may weigh more as you age or lose some of your youthful muscle tone.

Why has your shape gone south? A lower basal metabolic rate (BMR) is to blame. BMR is the number of calories you burn daily to fuel involuntary body functions, such as your heartbeat, brain function, and digestion. BMR is dependent upon body composition. The more muscle you have, the more calories you burn, 24 hours a day. That's because muscle is a high-maintenance tissue and requires more calories than fat to sustain itself.

The decline in muscle mass that begins in your twenties, coupled with a decrease in activity level, means that you need fewer calories in your sixties than you did in your teens. For example, a 180-pound male's BMR accounts for about 1,930 calories a day between the ages of 18 and 30.

After age 60, his body needs about 350 fewer calories to maintain his weight and good health. If you're still eating like a teenager by the time you're 60, and you haven't increased your physical activity, you'll definitely be putting on pounds.

For women, menopause often means weight gain. When the ovaries stop producing the hormone estrogen, muscle mass may diminish to the point of lowering BMR. When that happens, women gain a significant amount of fat, usually in the abdomen, even without consuming more calories.

Speaking of the abdomen, where you store extra fat also affects your health.

If you're shaped like an apple -- packing fat in your mid-section -- you're at greater risk for heart disease than if you're shaped like a pear -- gaining weight around your hips and buttocks. Excess weight in any location also boosts your chances for developing certain cancers and diabetes, and it also aggravates arthritis in your hips and knees.

Respiratory Changes

As you age, your lungs become less elastic, and your chest wall stiffens. In addition, the expansion of your trachea contributes to a decreased surface area in your lungs. You can't cough as forcefully, which also diminishes your ability to clear germs from your lungs. That's why older people are more prone to upper respiratory infections, such as colds.

If you ever smoked, your respiratory potential is reduced in your later years. Older adults also experience some difficulties with swallowing, which increases the chances of aspirating particles of food or other substances into the lungs. Aspiration is a common cause of pneumonia in older adults.

Lung capacity and function drop off with time, which means you may be more winded after climbing a flight of stairs or taking a walk than you were 20 years ago, but exercise heads off some of the changes to the lungs and entire respiratory system. Physically active older people who regularly participate in aerobic exercises, including walking and cycling, are way ahead of the curve.

Their aerobic capacity is far greater than their peers who don't exercise, and better than younger, sedentary people. In fact, well-conditioned older people may reach levels of lung function that exceed those of much younger people. A generous intake of vitamin C also helps maintain pulmonary function as you age. Loss of pulmonary function is a major predictor of disease and death in older adults.

Exercise Your Acumen

If new situations make you squirm, maybe you should exercise more often. What's the connection? As you age, it takes more time for your brain to process new information, so you may avoid unfamiliar surroundings for the sake of comfort. But that limits your world.

Regular exercise can help you expand your horizons. Studies show that the most physically fit older people best tolerate unfamiliar surroundings. Physical fitness helps you react more quickly to new situations, new faces, or a new social setting, perhaps adapting as quickly as someone much younger.

Continue to the next and final page of this article to learn about the sensory effects of aging and find out if you're at risk.

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Aging can also play havoc on your five senses. Read on to learn how sight, hearing, and even taste can deteriorate with age.

Eyesight and Aging

Are you holding your newspaper at arm's length? Squinting at documents to see the fine print? Do you need more light to see clearly? Each passing decade brings changes that weaken eyesight, including the slow loss of ability to focus on close objects or small print.

Presbyopia, the most common reason why you and your peers need reading glasses, is characterized by decreasing ability to focus on nearby objects. This condition typically shows up around age 40 but often develops for decades before that.

Some of the age-related eye changes are obvious, while others go undetected until vision is limited in some way. For example, the tissues surrounding eyes lose their tone, and fat is lost, too, which results in droopy upper eyelids and the turning outward or inward of the lower lid.

On the other hand, cataracts, which cloud your vision by keeping the light from getting through the clear lens of the eye, are barely detectable because they form at a snail's pace, are painless, and don't result in any redness or tearing in the eye. Over the years, the iris, the colored part of your eyeball, loses flexibility.

Your pupils -- the black holes in the iris that respond to light -- get smaller, and the lenses start to accumulate yellow substances, possibly as a result of exposure to sunlight. These changes predispose you to glaucoma, the product of excessive pressure inside your eyeball, which can lead to vision loss and blindness. No one knows the cause of glaucoma, but it is more prevalent in older people, African-Americans, and in those with a family history of the disease.

Glaucoma is basically symptom-free, often until it is too late. Once glaucoma has damaged the optic nerve, which transmits visual information from the eye to the brain, you're past the point of treatment. That's why The Glaucoma Foundation recommends testing for glaucoma every four years until age 45 and every two years after that. Get tested every two years regardless of age if:

Decreased blood flow to the retina, the paper-thin tissue lining the back of your eyeball, can lead to macular degeneration. Macular degeneration destroys sharp, central vision.Hearing and Aging

Find yourself saying "what?" more often? Maybe you don't like crowds as much since you can't detect the nuances of conversations that well. Hearing loss is one of the most common complaints of getting older, especially for men, who are more prone to hearing loss at any age.

Aging produces a progressive hearing loss at all frequencies, known as presbycusis. After age 55, your ability to detect changes in the pitch of sounds drops off dramatically, which can make your speech less understandable to others. In addition, the walls of your ear canal thin out, and earwax production falters.

Your eardrum thickens. You may even get arthritis in the joints that connect the bones found in the inner ear. Yet, no one knows for sure if these changes in hearing can be put down to the aging process. But it's certain that the loss of hair cells is what diminishes hearing the most.

Hair cells are part of the inner ear that help transmit impulses to a nerve that transfers them to your brain for processing. Nerve damage, injury, exposure to loud noise, and certain medications can cause hair cell loss.

Aging and Taste

You can thank your nose for your sense of taste, despite the thousands of taste buds populating your tongue: They can only detect a mere four out of thousands of possible flavors in foods.

The tongue recognizes only sweet, salty, bitter, and sour tastes. That's why enjoying food is limited without a healthy sense of smell. When you chew food and drink beverages, their aromas are released in your mouth.

Saliva dissolves flavor-producing substances in food and drink that make contact with your tongue's taste buds. More importantly, dissolved flavor compounds waft up the back of your throat, making their way to receptor cells in your nose. From there, nerves transmit flavor messages to the brain, allowing you to perceive and enjoy them.

If you're having trouble savoring the flavor of food, blame it on a lessened sense of smell. Time dulls your sense of smell, but not usually until you reach age 60, and then it varies from person to person. About half of adults over the age of 65 suffer from some diminished sense of smell. On the other hand, your sense of taste for sweet, salty, bitter, and sour foods may be remarkably intact until you're well into your seventies.

A zinc deficiency can also cause a decreased sense of taste. Zinc supplementation can help restore it if you do have a deficiency. Infections threaten sense of smell and, as a result, your ability to enjoy food. Some of the damage from the flu, colds, or hepatitis can be permanent. More often than not, acute illnesses, including sinus infections and seasonal allergies, block aromas from the receptor cells that relay flavor information to the brain.

As a result, you don't have as much capacity to savor the flavors of food. The pills you take every day to control medical conditions such as high blood pressure and arthritis can affect sense of taste, mainly by affecting the areas of the brain where you perceive flavors. Chemotherapy drugs and head and neck radiation also threaten flavor perception, sometimes permanently.

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ABOUT THE AUTHORS

Elizabeth Ward, M.S., R.D., is a nutrition consultant and writer. She is the author or coauthor of five books, including Super Nutrition After 50 and The Complete Idiot's Guide to Feeding Your Baby and Toddler. Ward is the nutrition editor of Muscle & Fitness Hers, a contributing editor for Environmental Nutrition, and a contributing writer for WebMD.com.

Jeffrey Blumberg, Ph.D., F.A.C.N., C.N.S. is a professor of nutrition science and policy and is the director of the Antioxidants Research Laboratory in the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University. In addition to publishing more than 180 research articles in peer-reviewed scientific journals, he has served on the Surgeon General's Workshop on Health Promotion and Aging, the Sports Medicine Committee of the U.S. Olympic Committee, the Board of the American Aging Association, the WHO/FAO Consultation on Preparation and Use of Food-Based Dietary Guidelines, the Food Advisory Committee of the FDA, and the WHO Expert Consultation on the Development of Nutrition Guidelines for the Elderly. He serves on the editorial board of several scientific journals, including the Journal of the American College of Nutrition, the Journal of Nutrition for the Elderly, the Journal of Medicinal Food, and Antioxidants & Redox Signaling.