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 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.

A reduction in immune response to infections has been demonstrated by older people's response to vaccines. For example, studies of influenza vaccines have shown that for people over age 65, the vaccine is less effective compared to healthy children over age 2.

But despite the reduction in efficacy, vaccinations for influenza and S. pneumoniae have significantly lowered the rates of sickness and death in older people when compared with no vaccination. 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. 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. Older people should discuss this question with their doctor.

Like any fighting force, the immune system army marches on its stomach. Healthy immune system warriors need good, regular nourishment. Scientists have long recognized that people who live in poverty and are malnourished are more vulnerable to infectious diseases.

For example, researchers don't know whether any particular dietary factors, such as processed foods or high simple sugar intake, will have adversely affect immune function. There are still relatively few studies of the effects of nutrition on the immune system of humans.

There is some evidence that various micronutrient deficiencies — for example, deficiencies of zinc, selenium, iron, copper, folic acid, and vitamins A, B6, C, and E — alter immune responses in animals, as measured in the test tube.

However, the impact of these immune system changes on the health of animals is less clear, and the effect of similar deficiencies on the human immune response has yet to be assessed.

So, what can you do? If you suspect your diet is not providing you with all your micronutrient needs — maybe, for instance, you don't like vegetables — taking a daily multivitamin and mineral supplement may bring other health benefits, beyond any possibly beneficial effects on the immune system.

Taking megadoses of a single vitamin does not. More is not necessarily better. Walk into a store, and you will find bottles of pills and herbal preparations that claim to "support immunity" or otherwise boost the health of your immune system.

Although some preparations have been found to alter some components of immune function, thus far there is no evidence that they actually bolster immunity to the point where you are better protected against infection and disease.

Demonstrating whether an herb — or any substance, for that matter — can enhance immunity is, as yet, a highly complicated matter. Scientists don't know, for example, whether an herb that seems to raise the levels of antibodies in the blood is actually doing anything beneficial for overall immunity.

Modern medicine has come to appreciate the closely linked relationship of mind and body. A wide variety of maladies, including stomach upset, hives, and even heart disease, are linked to the effects of emotional stress. Despite the challenges, scientists are actively studying the relationship between stress and immune function.

For one thing, stress is difficult to define. What may appear to be a stressful situation for one person is not for another. When people are exposed to situations they regard as stressful, it is difficult for them to measure how much stress they feel, and difficult for the scientist to know if a person's subjective impression of the amount of stress is accurate.

The scientist can only measure things that may reflect stress, such as the number of times the heart beats each minute, but such measures also may reflect other factors.

Most scientists studying the relationship of stress and immune function, however, do not study a sudden, short-lived stressor; rather, they try to study more constant and frequent stressors known as chronic stress, such as that caused by relationships with family, friends, and co-workers, or sustained challenges to perform well at one's work.

Some scientists are investigating whether ongoing stress takes a toll on the immune system. But it is hard to perform what scientists call "controlled experiments" in human beings.

In a controlled experiment, the scientist can change one and only one factor, such as the amount of a particular chemical, and then measure the effect of that change on some other measurable phenomenon, such as the amount of antibodies produced by a particular type of immune system cell when it is exposed to the chemical.

In a living animal, and especially in a human being, that kind of control is just not possible, since there are so many other things happening to the animal or person at the time that measurements are being taken.

Despite these inevitable difficulties in measuring the relationship of stress to immunity, scientists are making progress.

Almost every mother has said it: "Wear a jacket or you'll catch a cold! Probably not, exposure to moderate cold temperatures doesn't increase your susceptibility to infection.

There are two reasons why winter is "cold and flu season. Also the influenza virus stays airborne longer when air is cold and less humid. But researchers remain interested in this question in different populations. Some experiments with mice suggest that cold exposure might reduce the ability to cope with infection.

But what about humans? Scientists have performed experiments in which volunteers were briefly dunked in cold water or spent short periods of time naked in subfreezing temperatures. They've studied people who lived in Antarctica and those on expeditions in the Canadian Rockies.

The results have been mixed. For example, researchers documented an increase in upper respiratory infections in competitive cross-country skiers who exercise vigorously in the cold, but whether these infections are due to the cold or other factors — such as the intense exercise or the dryness of the air — is not known.

A group of Canadian researchers that has reviewed hundreds of medical studies on the subject and conducted some of its own research concludes that there's no need to worry about moderate cold exposure — it has no detrimental effect on the human immune system.

Should you bundle up when it's cold outside? The answer is "yes" if you're uncomfortable, or if you're going to be outdoors for an extended period where such problems as frostbite and hypothermia are a risk.

But don't worry about immunity. Regular exercise is one of the pillars of healthy living. It improves cardiovascular health, lowers blood pressure, helps control body weight, and protects against a variety of diseases.

But does it help to boost your immune system naturally and keep it healthy? Just like a healthy diet, exercise can contribute to general good health and therefore to a healthy immune system.

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Recent Blog Articles. Flowers, chocolates, organ donation — are you in? Lisa Valente is a registered dietitian and nutrition editor. She studied at the University of Vermont, where she completed her undergraduate studies in nutrition, food science and dietetics, and attended the dietetic internship program at Massachusetts General Hospital to become a registered dietitian.

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Lots of people are curious to know if there are foods out there that are natural immune boosters. The thing is, "boost" isn't really the right word. You can help support your immune system naturally with good nutrition and lifestyle habits, like trying to manage stress, getting enough sleep and regularly exercising.

But and there's a big but coming up No food or supplement is going to cure or prevent COVID, or any illness for that matter. There's a reason the CDC isn't advising everyone to arm themselves with chicken soup or a bottle of zinc pills and continue going about life as usual.

The best way to minimize the spread of illness in general is to avoid sick people and stay home if you're sick , wash your hands frequently, disinfect surfaces in your house and—when it comes to COVID in particular—get vaccinated and continue to follow the latest local and CDC guidelines on mask wearing.

Now that's out of the way. There are. Our immune system is supported by a generally healthy diet and also specific nutrients, namely vitamins A, C, D and E, as well as zinc. Protein is also important for immune health, as it helps to build and repair damaged immune cells note: most of us eat enough protein.

You can get all these nutrients from food. Vitamin D is probably the one nutrient on this list that's tough to find from food alone. Your body can also make vitamin D from sunlight. If you want to start supplementing, I would talk to your doctor or a dietitian and do your research read more about supplements and why they can be beneficial but also can be dangerous.

One key thing to remember, is that more isn't always better when it comes to these nutrients. Too much zinc can cause GI distress think nausea, vomiting and is also associated with suppressed immune function so, the opposite of what you're trying to do here.

Supplementing isn't necessarily the answer. You're not likely to get too much of any one nutrient from food, but on the other hand, it is easy to over supplement.

When it comes to getting good nutrition for your immune system, think of variety and balance in your diet. That, plus good hygiene habits, like washing your hands and regularly sanitizing surfaces, are the things that will help you naturally protect your immune system.

Getting the COVID vaccine is another way to help keep you safe. Some foods to consider:. Vitamin C-rich foods : peppers, oranges and orange juice, strawberries, broccoli, pineapple.

Vitamin D-rich foods : milk, yogurt, some fish, fortified foods. Zinc rich-foods : beans, nuts, seeds, meat, fish. Protein-rich foods : eggs, yogurt, meat, beans, fish, whole grains, cheese. We also know that gut health plays a role in immunity, so try to eat a mix of prebiotic and probiotic foods.

Think high-fiber prebiotics and fermented probiotics so vegetables, fruits, whole grains and yogurt, sauerkraut and kimchi. While whole foods are a healthy option, feel free to also rely on convenience items, like frozen and canned foods—especially if you're feeling under the weather and low on energy.

And if you're craving a plate full of comforting pasta or a cheesy casserole, then go for it. Our body does a pretty good job of letting us know what it needs, and a craving like that likely means your body needs some extra calories to cope.

Give yourself grace, definitely don't run to the store just to grab a food on this list and know that frozen and canned produce is a great way to get nutrients in your diet.

There's no research to show elderberry can help with COVID There's some research to show that elderberry may help with cold and flu symptoms , reducing both severity and duration.

However, we just don't know enough about it at this time and I wouldn't advise taking it right now but you know the drill—if you want to, chat with your doc first. Eating to support your immune system is about eating a variety of foods, so it's my opinion that all foods fit.

Alcohol isn't the best sorry to all you cocktail lovers. It's dehydrating and can affect your immune system negatively , so drink in moderation or skip it altogether.

Too much added sugar may also suppress your immune system temporarily according to research, but some is totally okay.