Have You Weakened Your Immune System?

Feeling run down? Are you frequently getting colds or flus? We all know taking Vitamin C can help give you a boost, but could you accidentally be suppressing your immune system without knowing it?

Our immune system is our shield against the bacteria and diseases from the outside world. There are two components to the immune system: innate immunity (the things you are born ‘equipped’ with, such as skin, body temperature, low pH levels and specialised cells, e.g. white blood cells), and acquired immunity which develops as your body encounters invading pathogens (B- and T- lymphocytes which excrete chemicals and control your immune response). If you find that you are regularly getting sick or run down you may be stopping your immune system from functioning to its full potential, here are some of the common causes:


Chronic stress, which is caused by stressful situations extended over a long period of time can cause cortisol levels to rise and inhibit the production of good prostaglandins, these are cellular messengers that support immune function and have anti-inflammatory properties. Our bodies trigger chemical reactions to various stimuli that we consider a ‘threat’, even it if it just something as simple as an exam. These chemical reactions still may have physical consequences, stressing our immune system (Miller, 2004). It is important to take time to relax and spend time de-stressing. Go for a walk, meditate, do something fun to help reduce those cortisol levels!

Lack of Sleep

Sleep loss may not only cause your immune system to operate below its optimum functionality, but can also influence how long your sickness will hang around for. A good amount (8-9 hours) of sleep regularly is essential for optimum physical and mental health and studies have shown that interactions between brain chemical systems and immune-signalling molecules are altered during sleep. However, if we are sleep deprived our T-cells decrease (T-Cells are responsible for ‘killing’ infected cells) and the amount of inflammatory cytokines in our bodies increase (a pro-inflammatory which promotes inflammation), this factor alone increases the risk of developing a cold or flu (Imeri & Opp, 2009).

Lack of Exercise

There is a considerable amount of research showing that a moderate amount of exercise on a regular basis enhances the function of the immune system, and a lack of exercise decreases the effectiveness of the immune system. People who are not exercising regularly are not able to take advantage of the increased production of macrophages (cells that attack bacteria which trigger upper respiratory diseases) that people who exercise regularly experience. The physiological changes in the immune system that happen when a person exercises promote more rapid circulation through the body, this effect is able to increase the rate at which viruses and bacteria can be destroyed. The increased circulation and macrophage production only lasts for a few hours after each session of exercise. More than 60% of people who exercise report fewer sicknesses than those who are sedentary (Nieman, 2000). It is important not overdo it however, positive changes to the immune system take place with moderate exercise, but too much exercise with too little rest can also decrease immunity.

Excess Use of Medications

Now, we are not saying “don’t take medication”, this is just a “watch out you’re not taking too much medication, but probably talk to your doctor about this we are just presenting the facts” haha. Excessive uses of antibiotics, cold and fever medications, steroid drugs and SSRIs have been found to weaken the immune system. All steroid drugs, from corticosteroids to anabolic steroids suppress the immune response; this is why it’s recommended you take a probiotic or immune support when you are on antibiotics. Even asthma inhalers contain synthetic steroids. Although the synthetic steroid is able to reduce inflammation in the airways it can still reduce the ability of the lungs to fight bacterial and viral infections (Journal of the American Medical Association, 2004). Selective Serotonin Reuptake Inhibitor antidepressant drugs (SSRIs) such as Zoloft and Prozac help to increase serotonin levels, but according to researchers at Georgetown University Medical Centre, this boost can push the immune system into overdrive and the body can begin attacking itself, leading to an autoimmune disease. Even long-term use of pain killing opioids such as codeine and morphine can seriously alter the effectiveness of the immune system against viral and bacterial invaders.


Dehydration is much more than just “not drinking enough water”, the side effects that result from being dehydrated can eventually be life threatening, and thus it is vital to maintain a good level of hydration. Water makes up a large percentage of blood, and a lack of hydration can cause the delivery of oxygen and nutrients to slow, and decrease immunity in the body (Vuong, 2004). Dehydration can allow cellular waste products to stay in the body for longer and can also have a negative effect on the brain. The brain continuously consumes a large amount of glucose, and this is delivered via the blood supply, so a lack of water means a lack of blood and glucose being delivered to the brain (Germain, 2006).

Fake Fragrances

Although most products that contain fake fragrances contain chemicals in small amounts, if you are regularly getting sick and none of the other factors seem to suit, perhaps take a look at these and limit your exposure to see if it makes a difference. Fake fragrances in products such as perfumes, colognes, deodorants, detergents and other beauty/cleaning products can be lung irritants and even cause asthma in children. Wearing fake fragranced clothing, sleeping in bed sheets washed in scented fabric softeners and having air fresheners around can definitely impact your lungs. For example, camphor which is found in perfume, shaving cream, nail polish and air fresheners is readily absorbed into body tissues, has been shown to be a local irritant and an irritant to the central nervous system (Kendall, 1997). A study titled Twenty Most Common Chemicals in Thirty-One Fragrance Products completed in 1991 also shows that a commonly used chemical a-terpineol, found in perfume, detergent, fabric softener, air freshener, hairspray and deodorants is highly irritating to mucous membranes, can cause headaches and repeated or prolonged skin contact should be avoided.


I don't think we even need to explain this one!

Excess Refined Sugar

When your body is fighting an infection your white blood cells “swallow” the viruses and bacteria. In order to be able to do this your white blood cells need to have a very high amount of Vitamin C. The problem with consuming too much refined sugar, or even letting your blood sugar level exceed 120, is that your white blood cells confuse glucose (sugar in the blood stream) with vitamin C as they are chemically very similar. When your white blood cells are taking in glucose instead of vitamin c, their vitamin c level is not high enough to effectively combat bacteria and viruses. In fact, their ability to destroy the invading pathogens is reduced by up to 75% (Afkani-Ardekani, Shojaoddiny-Ardekani, 2007). Once your blood sugar level is back below 120 it can take a further 4-6 hours for your white blood cells to regain the amount of vitamin c they need to be completely effective again. Therefore, if you are consistently eating products with lots of refined sugar, and allowing your blood sugar levels to spike frequently, you’re actually reducing your body’s ability to fight off infection and bacteria.

Bad Diet

Following on from refined sugar, a bad diet in general can suppress the body’s immune response. People who are eating very low calorie diets (~1200kcal per day, often found in many popular meal plans nowadays) are at greater risk of infection and have decreased immune function compared to those eating an appropriate amount of calories per day (Wikstrand, Torgerson & Brostrom, 2010). Conversely, excessive calorie intake (overeating) can also have a negative effect on the immune system. Obesity is linked to an increased rate of disease (Karlsson, Sjostrom & Sullivan, 1998). Diets that are high in saturated fats appear to suppress the response of the immune system, and therefore increase the rate of infections. It is important to have a balanced diet full of fruits, vegetables and wholegrains, limit the intake of saturated fats (not all fats, your body does need ‘good’ fats for brain function, check our Get Lean guide to learn more), and restrict the amount of refined sugar you include in your diet.

Zinc Deficiency

Studies conducted by Oregon State University are showing that Zinc appears to effect immune response in the human body. Particularly when it comes to inflammation.

Reference List:

2001, ‘Does exercise alter immune function and respiratory infections?’ Research Digest, vol. 3, no. 13.

Afkhami-Ardekani, M & Shojaoddiny-Ardekani, M 2007, ‘Effect of vitamin c on blood glucose, serum lipids, and serum insulin in type 2 diabetes patients’, Indian Journal of Medical Research, vol. 126, pp. 471-474.

Germain, R et al 2006, ‘Dynamic imaging of the immune system: progress, pitfalls and promise’, Nature Reviews Immunology, pp. 497-507.

Imeri, L & Opp, M 2009, ‘How (and why) the immune system makes us sleep’, Nature Reviews Neuroscience, vol. 10, pp. 199-210.

Karlsson, J, Sjostrom, L & Sullivan, M 1998, ‘Swedish obesity subjects (SOS) – an intervention study of obesity. Two-year follow-up of health-related quality of life (HRQL) and eating behaviour after gastric surgery for severe obesity’, International Journal of Obesity and Related Metabolic Disorders, vol. 22, no. 2, pp. 113-126.

Kendall, J 1997, ‘Twenty most common chemicals in thirty-one fragrance products based on a 1991 EPA study’ Health Hazard Information. Neiman, D et al 2000, ‘Immune function in female elite rowers and nonathletes’, British Journal of Sports Medicine, vol. 34, pp. 181-187.

Segerstrom, S & Miller, G 2004, ‘Psychological stress and the human immune system. A meta-analytic study of 30 years of inquiry’, Psychol Bull, vol. 130, no. 4, pp. 601-630.

Shankar, A & Prasad, A 1998, ‘Zinc and immune: the biological basis of altered resistance to infection’, American Journal of Clinical Nutrition, vol. 68.

Vuong, C et al 2004, ‘Polysaccharide intercellular adhesion (PIA) protects Staphylococcus epidermis against major components of the human innate immune system’, Cellular Microbiology, doi: 10.146/j.1462-5022.2004.00367.x.

Wikstrand, I, Torgerson, J & Bostrom, K 2010, ‘Very low calorie diet (VLCD) followed by a randomised trial of corset treatment for obesity in primary car’, Scandinavian Journal of Primary Health Care, vol. 28, no. 2, pp. 89-94.