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Factors that Lower the Immune System and 5 Immune Boosting Nutrients

Let's first review some common causes of a lowered immune system and why you may be more susceptible to a cold or flu in the first place.
Nov 4, 2014 | Joy McCarthy

I was at the shopping mall the other day and I noticed the number of people sneezing and sniffling. My natural instinct is avoidance (stay as far away from the sick person as possible) and then wash my hands as soon as I can. I simply can't do what I do as a nutritionist if I'm not feeling healthy and vibrant. No one wants to be consulted by a sick nutritionist or hear one speak! Sick days are just not an option. If I put my holistic nutritionist hat on I must remind myself that it's the terrain (meaning, the health of my own body that wards off sickness), NOT the germ.

There is more to the story because a healthy terrain is more than just avoiding someone who is sick. It is a truly a holistic approach.

Let's first review some common causes of a lowered immune system and why you may be more susceptible to a cold or flu in the first place.


Factors that lower immunity

1. Lack of sleep.

Studies show people who lack adequate sleep (those getting 6 hrs or less) or shift workers are far more prone to the common cold and flu. Your immunity soldiers are affected -- reduced natural killer cell activity, suppressed interleukin-2 production and increased levels of circulating pro-inflammatory cytokines -- this is all bad news for your immune system.

This is why I personally love and recommend Pascoflair to my clients. It is one of my favourite herbs, passionflower, which helps you relax and ensure a restful sleep. It helps to calm your monkey brain and ease restlessness both of which reduce anxiety and help you sleep. The best part is it works as effectively as prescribed medication minus the negative side effects.

2. Sugar.

The Standard American Diet is loaded with processed foods and refined sugars. This is a feast for the bad guys -- bad bacteria, yeast and fungi thrive on sugars. Since your gut is home to 70% of your immune system, an overgrowth of the bad guys can seriously hamper your immune system function. Also, when white blood cells, the defenders of the immune system, are exposed to high levels of sugar, their ability to fight bacteria decreases significantly, which makes the body more prone to ALL infections.

Adding insult to injury, sugar causes nutrient depletions of B-vitamins, vitamin C. You can read about more Negative Effects of Sugar. This is why I recommend the Joyous 10-day Detox to everyone I can -- 10 days of no sugar can do wonders for your body. And the best part, most people have no idea how good their body is designed to feel which is a great motivating factor to continue after the 10 days is done.

3. Drinking alcohol excessively or binge drinking.

While you may not consider yourself an excessive or binge drinker, if you are someone who goes out on weekends and has 4-5 drinks in one evening then you fit into this category. Alcohol impairs your immune system by reducing function of T and B lymphocytes, natural killer cells and monocytes and macrophages, decreasing the inflammatory response and altering cytokine production -- translation? Alcohol is horrible for your immune system. Moderate alcohol consumption has been shown to have the opposite effect - hurray for those who like an occasional glass of red wine. Thanks to those antioxidants that are beneficial to your immunity.

4. Stress.

Stress is the number cause of illness so it's no surprise that studies show psychological stress has also been shown to increase susceptibility to viral infection. Subjects exposed to stress showed increased infection rates from 74% to 90%, and colds rose from 27% to 47%. Stress also leads to the release of histamines, which can trigger severe bronchial constriction in asthmatic. You've likely noticed when you are in the midst of a crisis or major deadline at work you get through it and then get sick. This is because you are likely secreting massive amounts of adrenalin to keep you going and as soon as that stimulus goes away and you have a chance to relax you get sick. Get stress busting tips here and learn tips to shake it off!

Other factors to consider: Smoking, second hand smoke, exposure to chemicals and heavy metals, too much exercise.

There will always be times in life where you are not sleeping like a baby and demands at work and/or home-life are at an all-time high. This is why it's important to make sure you make it a priority to get these five immune boosting nutrients.

5 Immune boosting nutrients

1. Vitamin D

The sunshine vitamin! One of the many functions of vitamin D is to help the body better identify and destroy bacteria and viruses. Unfortunately more people need to supplement because between 40-70% of Canadians are vitamin D deficient during the winter months.

Food sources: mushrooms, salmon, sardines
Supplement: D3 - capsule or liquid is best.

2. Healthy Bacteria

The function of healthy bacteria is to train the immune system. 70-80% of your immune system lives in your gut. The beneficial bacteria that call your body home have many roles:

  • Help train the immune system to differentiate friend (food) from foe (pathogens, toxins)
  • Rebalance the immune system when it gets out of whack
  • Reduce gut inflammation
  • Limit the amount of bad/pathogenic bacteria in the gut
  • Food sources: kimchi, miso, tamari, yogurt, kefir, kombucha


3. Vitamin C

The function of Vitamin C is believed to act against cold viruses by stimulating the white blood cells which defend the body against viruses. Vitamin C is also incredibly protective to the damaging effects of stress which you already know lowers the immune system! Humans, unlike other animals do not make vitamin C. Interestingly, when animals are exposed to stress they significantly increase vitamin C production in the body. Since we can't make it we need to consume foods that are high in vitamin C every single day by eating at least 5 to 6 servings of fruits and vegetables. If you do a lot of air travel, then you definitely need to make sure a vitamin C supplement is part of your daily regime to stay healthy.

Food sources: Citrus, brussels sprouts, bell peppers, leafy greens, dark berries, especially goji berries.

4. Protein

Protein helps the immune system because it makes antibodies that fight off infection. Much research has shown that protein malnutrition can have a variety of negative effects on the immune system. Research has shown that deficiency of high-quality protein can result in depletion of immune cells, inability of the body to make antibodies, and other immune-related problems. In addition, animal studies have shown that the immune system can be significantly compromised with even a 25% reduction in adequate protein intake. Source:

Food sources: Eggs, fish, chicken, chick peas, lentils, beans, nuts and seeds, tempeh, protein powder. The recipe ideas are endless on the joyous health blog and in my book joyous health!

5. Happiness.

Yes! Happiness is absolutely a nutrient. Countless studies show that a positive attitude and optimistic outlook help to lower the negative effects of stress. As mentioned previously it is a well known fact that stress lowers the immune system.

A study with the common cold and emotions showed that participants with happy emotions exhibited a greater ability to fight off the cold when given a squirt of the rhinovirus!

Sources: Hugs, self-care such as yoga and meditation, gratitude, reading the Joyous Health blog (hopefully!!)

Here's a summary for you...

You can watch the segment from the Morning Show here, that summarizes many of these points:

Karin   •   November 4, 2014

Hi Joy, Saw the morning show today, such great info, thanks for sharing! I especially love kamboucha! Do you have any recipes on how to make your own at home? Thanks! Ciao! Karin

Kate McDonald Walker   •   November 5, 2014

Judy Hill   •   November 5, 2014

How could people not be happy and want to change their lifestyles after watching this! Joy your name suits you to a tee! I love your common sense approach to everyday life and you just make me smile!


Beth johnson   •   November 5, 2014

Such amazing tips! I suffered from an extremely weak immune system and when I corrected my nutritional deficiencies and reduced my stress levels I stopped getting sick!


Mikhaila   •   November 9, 2014

Aloha from Hawaii, I love this. I am just discovering your site and I love it !!! I also loved olive leaf extract to help me get through the flu recently !!! Mikhaila :)


Heather   •   November 17, 2014

I really liked this article - perfect timing with the seasons changing too! I notice a ton of people around me are getting sick so I was just Googling "how to boost your immune" when this popped up :) so thanks! Also, for anyone wondering about #5 above - I once read that disease and sickness can only happen on a low frequency; which negative thoughts also lower your body's frequency, so it's actually 'scientifically true' ! Real food (veggies/fruit/nuts) actually raise your body's frequency level, so sickness cannot thrive. Cool stuff!


Melinda LaHaye   •   January 6, 2018

Do you have any studies that I can show my friend about the sugar suppressing the immune system?

Rachel Molenda   •   January 11, 2018

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