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. As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles.

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Every part of your body, including your immune system, functions better when protected from environmental assaults and bolstered by healthy-living strategies such as these: Don't smoke.

Animal studies have found that deficiencies in zinc , selenium , iron , copper, folic acid , and vitamins A , B6 , C , D , and E can alter immune responses.

Epidemiological studies find that those who are poorly nourished are at greater risk of bacterial, viral, and other infections. Eating a good quality diet, as depicted by the Healthy Eating Plate, can prevent deficiencies in these nutrients.

However, there are certain populations and situations in which one cannot always eat a variety of nutritious foods, or who have increased nutrient needs. In these cases a vitamin and mineral supplement may help to fill nutritional gaps.

Studies have shown that vitamin supplementation can improve immune responses in these groups. The elderly are a particularly high-risk group. The immune response generally declines with increasing age as the number and quality of immune cells decreases. This causes a higher risk of poorer outcomes if the elderly develop chronic or acute diseases.

In addition, about one-third of elderly in industrialized countries have nutrient deficiencies. Diet variety may also be limited due to budget constraints or lower interest in cooking for one person; poor dentition; mental impairment; or lack of transportation and community resources to obtain healthy food.

Megadose supplements many times the RDA do not appear justified, and can sometimes be harmful or even suppress the immune system e. 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? Diet Review: Anti-Inflammatory Diet. Food Safety, Nutrition, and Wellness during COVID Ask the Expert: The role of diet and nutritional supplements during COVID The contents of this website are for educational purposes and are not intended to offer personal medical advice.

You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. The Nutrition Source does not recommend or endorse any products.

Skip to content The Nutrition Source. The Nutrition Source Menu. Search for:. Home Nutrition News What Should I Eat? What Is Our Immune System? These barriers include: Skin that keeps out the majority of pathogens Mucus that traps pathogens Stomach acid that destroys pathogens Enzymes in our sweat and tears that help create anti-bacterial compounds Immune system cells that attack all foreign cells entering the body Adaptive or acquired immunity is a system that learns to recognize a pathogen.

Other conditions that trigger an immune response Antigens are substances that the body labels as foreign and harmful, which triggers immune cell activity.

What factors can depress our immune system? Older age: As we age, our internal organs may become less efficient; immune-related organs like the thymus or bone marrow produce less immune cells needed to fight off infections. Aging is sometimes associated with micronutrient deficiencies, which may worsen a declining immune function.

Environmental toxins smoke and other particles contributing to air pollution, excessive alcohol : These substances can impair or suppress the normal activity of immune cells.

Excess weight: Obesity is associated with low-grade chronic inflammation. Fat tissue produces adipocytokines that can promote inflammatory processes. Chronic diseases: Autoimmune and immunodeficiency disorders attack and potentially disable immune cells.

Chronic mental stress: Stress releases hormones like cortisol that suppresses inflammation inflammation is initially needed to activate immune cells and the action of white blood cells.

Lack of sleep and rest: Sleep is a time of restoration for the body , during which a type of cytokine is released that fights infection; too little sleep lowers the amount of these cytokines and other immune cells. Does an Immune-Boosting Diet Exist?

Nothing good ever comes from smoking. Its many negative health impacts include weakening your immunity. This means if you smoke tobacco, you're more likely to get bacterial and viral infections.

Get support to quit smoking today. There isn't a single nutrient or food that will boost your immunity on their own. Take up the fight to protect your immunity by eating foods rich in essential vitamins and minerals such as vitamins A, B6, B12, C, D and E, and copper, folate, iron, selenium and zinc.

According to the Baker Heart and Diabetes Institute, you can also bolster your immunity by avoiding high-sugar and ultra-processed foods, and not drinking excess amounts of alcohol. How does immunity work? The immune system guards your body against germs, harmful substances and cell changes that can cause infection.

Its main job is to act quickly to ensure invaders don't make you sick. When your immunity is weak or can't fight aggressive germs you may get ill. Still having trouble warding off nasty germs?

Boost your super-health powers by adding exercise to your daily habits. According to studies , moderate exercise can help to improve your immunity's defence. Follow the Australian Government guidelines and aim to get active every day. You'll need to do up to 5 hours of moderate exercise or up to 2.

Another way to make you less vulnerable to infections is quality sleep. If you're aged , you're recommended to have hours of sleep each night to feel refreshed and function at your best the next day. Organise your bedroom and routine for a good night's sleep. There are many ways you can manage this, such as:.