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The effects of aging on your immune system

Does it seem like you get sick more than you did when you were younger?

When you are under the weather, does it take you longer to feel good again?

Immunity tends to get weaker with age. Just as you probably can’t run as fast as you used to in your 20s, your immune system doesn’t work as well as it used to.


But fear not!


Compared to many other bodily functions, most people’s immune systems actually do really great at any age. Most of our immune systems work well enough that our risk for infection and illness isn’t much higher than normal. Even better? No matter how old you are, there’s a lot you can do to stay healthy.


What’s Happening With Your Immune System?

It’s a complex network of cells, tissues, and organs. Together, they defend your body against things that can cause infection, like bacteria.


What researchers do know is that most older adults:

  • Don’t respond as well to vaccines: Your immune system includes T cells, which attack other, illness-causing cells. They’re able to “remember” an invader, then defend against it better later. When you’re older, you make fewer T cells, and most vaccines require new ones to work. The exception? The shingles vaccine. That’s one of the reasons it works so well for the senior set.

  • Are more likely to get sick: Not only do you have fewer immune cells as you age, the ones you do have don’t communicate with each other as well. That means they take longer to react to harmful germs.

  • Recover from injuries, infection, and illness more slowly: Your body produces fewer immune cells, including white blood cells.


How Can You Stay Healthy?

  1. Stay on top of your health. If you have diabetes, arthritis, or other things that affect how you feel and function, follow your doctor’s recommendations. Keeping illnesses like diabetes well-controlled takes less of a toll on your immune system.

  2. Sleep well. Research clearly shows that too little sleep -- or poor-quality sleep -- lowers immunity, even in young healthy people. You should be getting at least 7 hours a night. If you snore or have trouble falling or staying asleep, see your doctor. You could have a sleep disorder.

  3. Look for ways to reduce stress. Over time, stress may lessen your immune response. When you’re constantly worried about something, it takes a toll on your body. It can also trigger other issues, like poor sleep and a bad diet, which both may affect your immunity.

  4. Move more often. Exercise has a profound effect on the immune system (see below).

  5. Eat well. There’s no one diet that improves immunity. But researchers do know that a varied diet full of vitamin- and mineral-rich foods (like fresh vegetables and fruit) helps your body -- including your immune system -- function at its best. Eating a healthy diet also helps you weigh what you should, which may put less stress on your body and improve immunity.

  6. Don’t smoke. Smoking weakens your body’s immune response, making you more susceptible to illness and infection.

Boosting Your Immune System

Many products on store shelves claim to "boost" or support immunity. But the concept of boosting immunity actually makes little sense scientifically.


Attempting to boost the cells of your immune system is especially complicated because there are so many different kinds of cells in the immune system that respond to so many different microbes in so many ways. Which cells should you boost, and to what number?


So far, scientists do not know the answer. What is known is that the body is continually generating immune cells. Certainly, it produces many more lymphocytes than it can possibly use. The extra cells remove themselves through a natural process of cell death called apoptosis — some before they see any action, some after the battle is won. No one knows how many cells or what the best mix of cells the immune system needs to function at its optimum level.


As we age, our immune response capability becomes reduced, which in turn contributes to more infections and more cancer. As life expectancy in developed countries has increased, so too has the incidence of age-related conditions.


While some people age healthily, the conclusion of many studies is that, compared with younger people, the elderly are more likely to contract infectious diseases and, even more importantly, more likely to die from them. Respiratory infections, including, influenza, the COVID-19 virus and particularly pneumonia are a leading cause of death in people over 65 worldwide. No one knows for sure why this happens, but some scientists observe that this increased risk correlates with a decrease in T cells, possibly from the thymus atrophying with age and producing fewer T cells to fight off infection. Whether this decrease in thymus function explains the drop in T cells or whether other changes play a role is not fully understood. Others are interested in whether the bone marrow becomes less efficient at producing the stem cells that give rise to the cells of the immune system.


There appears to be a connection between nutrition and immunity in the elderly.

A form of malnutrition that is surprisingly common even in affluent countries is known as "micronutrient malnutrition." Micronutrient malnutrition, in which a person is deficient in some essential vitamins and trace minerals that are obtained from or supplemented by diet, can happen in the elderly. Older people tend to eat less and often have less variety in their diets. One important question is whether dietary supplements may help older people maintain a healthier immune system.


Each stage of the body’s immune response relies on the presence of many micronutrients. Examples of nutrients that have been identified as critical for the growth and function of immune cells include vitamin C, vitamin D, zinc, selenium, iron, and protein (including the amino acid glutamine). They are found in a variety of plant and animal foods.


The gut is a major site of immune activity and the production of antimicrobial proteins. The diet plays a large role in determining what kinds of microbes live in our intestines. A high-fiber plant-rich diet with plenty of fruits, vegetables, whole grains, and legumes appear to support the growth and maintenance of beneficial microbes. Certain helpful microbes break down fibers into short chain fatty acids, which have been shown to stimulate immune cell activity. These fibers are sometimes called prebiotics because they feed microbes. Therefore, a diet containing probiotic and prebiotic foods may be beneficial. Probiotic foods contain live helpful bacteria, and prebiotic foods contain fiber and oligosaccharides that feed and maintain healthy colonies of those bacteria.


  • Probiotic foods include kefir, yogurt with live active cultures, fermented vegetables, sauerkraut, tempeh, kombucha tea, kimchi, and miso.

  • Prebiotic foods include garlic, onions, leeks, asparagus, Jerusalem artichokes, dandelion greens, bananas, and seaweed. However, a more general rule is to eat a variety of fruits, vegetables, beans, and whole grains for dietary prebiotics.

A general multivitamin/mineral supplement providing the recommended dietary allowances (RDA) may be used. However, megadose supplements (many times the RDA) do not appear justified and can sometimes be harmful or even suppress the immune system (e.g., as with zinc). Remember that vitamin supplements should not be considered a substitute for a good diet because no supplements contain all the benefits of healthful foods.


Several herbal supplements have been suggested to boost immune function. What does the research say?

  • Echinacea: Cell studies have shown that echinacea can destroy influenza viruses, but limited research in humans has been inconclusive in determining echinacea’s active components. Taking echinacea after catching a cold has not been shown to shorten its duration, but taking it while healthy may offer a small chance of protection from catching a cold.

  • Garlic: The active ingredient in garlic, allicin sativum, is proposed to have antiviral and antimicrobial effects on the common cold, but high-quality clinical trials comparing garlic supplements to placebo are lacking. A Cochrane review identified only one trial of reasonable quality following 146 participants. Those taking the garlic supplement for 3 months had fewer occurrences of the common cold than those taking a placebo, but after contracting the cold virus, both groups had a similar duration of illness. Note that these findings are from a single trial, which needs to be replicated.

  • Tea catechins: Cell studies have shown that tea catechins such as those found in green tea can prevent flu and some cold viruses from replicating and can increase immune activity. Human trials are still limited. Two randomized controlled trials found that green tea capsules produced less cold/flu symptoms or incidence of flu than a placebo; however both studies were funded or had author affiliations with tea industries.

  • Elderberry: While many believe that elderberries are a good solution for boosting immunity, the National Center for Complementary and Integrative Health says, “There’s not enough information to show whether elderberry is helpful for any other health purposes.”

A study led by Michael Macknin, MD, professor emeritus of pediatrics at Cleveland Clinic Lerner College of Medicine, is the largest one to date that has been done to evaluate how elderberry is used in the treatment of patients with influenza B.


Influenza A and B are the two main types that cause seasonal flu epidemics. Influenza A can be very harmful and cause pandemics. Influenza B isn’t as common and is far less likely to cause pandemics. While influenza A can be transmitted by birds and other animals, influenza B is mostly found in people.


The study examined 87 patients age 5 and above who tested positive for influenza, or the flu, between January 2018 and April 2019. Only 33% of patients in the study had received flu vaccines.


Patients had two or more of the following symptoms: body aches, chills, cough, fatigue, headaches, nasal congestion or sore throat. They were evaluated in an emergency room setting where they were randomly assigned to receive elderberry extract or a placebo for 5 days. They had the option to take the antiviral drug oseltamivir (Tamiflu) as well.


Patients between the ages of 5 and 12 received a placebo or 15 ml (5.7 g) of elderberry extract orally twice a day for five days. Patients over the age of 12 received 15 ml of elderberry extract four times a day for five days.


The results of the study showed no difference in the severity or duration of flu symptoms between the elderberry and placebo groups. For those in the elderberry group who didn’t take oseltamivir, it took two extra days for symptoms to subside compared to the placebo group. This contradicts previous studies which found that elderberry shortened flu symptoms by four days, demonstrating the need for further research.


  • Vitamin C: Our bodies don't make vitamin C, but we need it for immune function, bone structure, iron absorption, and healthy skin. We get vitamin C from our diet, usually in citrus fruits, strawberries, green vegetables, and tomatoes. The Recommended Dietary Allowance for men is 90 milligrams (mg) per day, and for women, it's 75 mg per day. Vitamin C appears to be able to both prevent and treat respiratory and systemic infections by enhancing various immune cell functions. Prophylactic prevention of infection requires dietary vitamin C intakes that provide at least adequate, if not saturating plasma levels (i.e., 100–200 mg/day), which optimize cell and tissue levels. In contrast, treatment of established infections requires significantly higher (gram) doses of the vitamin to compensate for the increased metabolic demand.

Ensuring adequate intake of vitamin C through the diet or via supplementation, especially in groups such as the elderly or in individuals exposed to risk factors for vitamin C insufficiency, is required for proper immune function and resistance to infections.

  • Zinc: Zinc is believed to prevent cold viruses from spreading and by reducing inflammation, which may shorten the duration of a cold. Research has shown mixed results of their effectiveness due to differences in the form of zinc, the dosage, and how long it was used. Yet some clinical trials support its effectiveness. A Cochrane review of clinical trials found that zinc lozenges did not prevent colds, but if taken within a day of the onset of cold symptoms (sore throat, sniffles), the lozenges could tame its severity. However, it is noted that some of the trials were funded by pharmaceutical companies who may have had financial interest in or produced zinc lozenges.

Because zinc supports the growth and normal functioning of immune cells, even a mild or moderate deficiency can slow down the activity of lymphocytes, neutrophils, and macrophages that protect the body from viruses and bacteria.


The importance of exercise

Exercise has a profound effect on the immune system.


Inevitably, people become less physically active as they age, but there is evidence to suggest that getting as much exercise as possible can slow or even reverse some of the effects of immunosenescence.


Skeletal muscle produces a range of proteins called myokines that reduce inflammation and preserve immune function. Therefore, it makes sense that maintaining muscle mass through exercise protects against infection and conditions such as type 2 diabetes and cardiovascular disease, which are closely linked to chronic inflammation.


One study found that aerobic fitness among 102 healthy males, aged 18–61 years, was inversely proportional to the number of senescent T cells in their blood after adjusting for age. In other words, increased physical fitness was associated with less immunosenescence.


The fittest males not only had fewer senescent T cells but a greater number of naïve T cells.


Another study compared the immune responses of 61 healthy males, aged 65–85 years, to a flu vaccination. Around one-third of the males were intensively active (though participation in running or sports), one-third were moderately active, and one-third were mostly inactive.


After adjusting for their age, the researchers found that the intensively and moderately active males produced more antibodies in response to vaccination than the least active males.


Remarkably, the more active males had higher serum concentrations of antibodies to some flu strains even before they underwent vaccination.


A range of other studies have identified similar benefits, not only from long-term physical activity but also from single bouts of exercise before vaccination.


These studies suggest that the emergence of certain features of immunosenescence and the extent of immune remodeling is likely to be heavily influenced by insufficient physical activity as humans age.


In other words, GET MOVING!



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