Vitamins For Cold And Flu

  • Maariya Rachid Daud Doctor of Philosophy - PhD, Bioprocessing and Chemical Engineering, The University of Manchester
  • Richa Lal MBBS, PG Anaesthesia, University of Mumbai, India

Overview

As winter approaches, it is essential to strengthen your immune system to fight off cold and flu viruses. The common cold and flu are respiratory infections that strike millions worldwide during the colder months. These illnesses, while considered common, can disrupt daily life and pose health risks if not addressed. However, our immune system acts as a powerful defence mechanism against these viruses, making the immune system crucial during the cold and flu seasons. 

In this article on “Vitamins for Cold and Flu,” we explore the power of essential nutrients like vitamin C, zinc, vitamin D, and more, known for boosting immunity. With evidence-based strategies, you can prepare yourself for a healthier winter season and stay ahead in the battle against cold and flu. Our comprehensive guide will unlock the potential of vitamins in supporting your well-being and promoting a strong immune response. 

Understanding cold and flu

The common cold and flu are both contagious respiratory illnesses that target the upper respiratory tract, including the nose, throat, and more.1 Despite affecting the same area, they are caused by distinct viruses. Influenza, or the flu, originates from the influenza virus. There are four types of influenza viruses: A, B, C and D. The flu is primarily caused by influenza types A and B.2 Whereas the common cold can be triggered by various viruses, such as rhinoviruses, parainfluenza, and seasonal coronaviruses (not to be confused with COVID-19's SARS-CoV-2), with the most common virus being the rhinovirus. It has been found that almost 50% of all colds are associated with rhinovirus.3 

You can catch the cold and flu all year round, but it is especially common in the winter seasons. A recent study has found that cold weather damages our body’s immune response in the nose. Research indicates that a decrease of approximately 5 degrees Celsius in temperature inside the nostrils can lead to the destruction of nearly 50% of the virus-fighting cells present.4 

Cold and flu viruses spread through direct contact, when infected individuals release air droplets, and others inhale them. Air droplets can be made by coughing, sneezing, and even talking! Indirect contact occurs when air droplets containing the viruses land on surfaces like doorknobs, handrails, or utensils, and healthy individuals touch their faces, unknowingly introducing the virus into their bodies. 

Symptoms of cold and flu

As the symptoms of cold and flu overlap, it can be difficult to distinguish between them based on symptoms alone. The common cold's incubation period is usually 1 to 3 days. This means it takes about that much time from when you catch the virus until you start feeling the symptoms.5 Symptoms usually consist of a runny or stuffy nose, mild cough, sneezing, and headaches, in addition to tiredness and body aches. Generally, people recover from a cold within seven to ten days; however, symptoms can last up to two weeks. As with the common cold, symptoms of the flu can appear abruptly 2 days after exposure.6 

While symptoms of the common cold and flu can be similar, the symptoms of the flu tend to be more severe. Other flu symptoms, which differentiate themselves from a cold, include a fever (37.8 degrees Celsius), chills, diarrhoea, nausea, vomiting, a loss of smell and/or taste, and eye symptoms such as photophobia - extreme sensitivity to light.6 Given the severity of the cold, a complete recovery takes around 2 weeks. 

Here is a side-by-side table that gives an overview of the similarities and differences.

Is it a cold or a flu?
Signs and SymptomsColdFlu
OnsetRapid1-3 days
FeverCommonRare
ChillsSometimesRare
CoughCommonCommon
HeadacheSometimesSometimes
Muscle achesCommonMild
FatigueCommonMild
Stuffy/Runny noseSometimesCommon
SneezingRareCommon
Sore ThroatSometimesCommon
NauseaSometimesNo
DiarrhoeaSometimesNo
EaracheSometimesSometimes

Essential vitamins for colds and flu

Having a strong and healthy immune defence system can help reduce the occurrence and severity of symptoms and/or duration of the common cold and flu. The evidence regarding the benefits of supplements is often mixed; however, generally, it shows a positive effect.

Vitamin C

Vitamin C, ascorbic acid, is commonly marketed as the go-to supplement for preventing cold and flu. Vitamin C is a powerful water-soluble antioxidant that helps boost the immune system and enhances the ability to fight infections. In addition, it supports the body’s physical barrier (i.e. the skin) that protects us from the virus.7 Vitamin C is not naturally produced or stored in the human body; therefore, it is an essential dietary requirement. An adult's recommended daily amount (RDA) of vitamin C is 40mg/day.

In 2013, a meta-analysis was conducted to examine the impact of vitamin C on the cold and flu.8 The study found that when individuals start taking vitamin C after catching a cold, it may not provide significant benefits. Some studies suggest that very high doses may slightly reduce the duration of colds and flu; however, further research would need to be conducted for confirmation. In addition, for those who regularly take vitamin C, the duration of colds can be slightly shorter, with an 8% reduction in adults and 14% in children, along with milder symptoms.

Athletes who consistently take vitamin C are less likely to catch a cold, experiencing a 50% decrease in risk compared to those who don't take the supplement. This benefit is particularly noticeable among individuals who regularly or intensely exercise.8

The main food sources of vitamin C include:

  • Citrus Fruits–Oranges, grapefruits, lemons, limes, and tangerines
  • Berries –Strawberries, blueberries, raspberries, blackberries, and cranberries
  • Peppers
  • Leafy Greens–Spinach and kale
  • Broccoli
  • Tomatoes
  • Kiwi
  • Pineapple

Vitamin D

Vitamin D is involved in many cellular processes in the body. It is widely known that it helps regulate the amount of calcium and phosphate in the body, which is required for healthy bones, teeth, and muscles. It is also involved in the regulation of immune cells.9 It is sometimes referred to as the “sunshine vitamin” as the sun is our main source of vitamin D and contributes to 80-100% of our recommended daily dose. Regardless, it can still be found in a variety of food sources, such as

  • Fatty fish– salmon, mackerel, tuna, and sardines
  • Cod Liver Oil
  • Egg – especially the yolk
  • Cheese–Certain types of cheese, such as Swiss and cheddar, contain vitamin D in smaller amounts
  • Mushrooms–Some varieties of mushrooms are exposed to ultraviolet (UV) light during processing, which increases their vitamin D content
  • Fortified plant-based Milk–Almond, soy, and oat milk fortified with vitamin D

In Spain, a study showed that in the warmer seasons, about 8 to 10 minutes of sun exposure at noon produced the recommended amount of vitamin D. However, it takes nearly 2 hours of sun exposure at noon in the winter season to produce a sufficient amount of vitamin D.10 However, for people who live in higher altitudes, such as the UK, there is a high risk of having low vitamin D levels in the winter. More than half of the UK population has been found to have insufficient levels of vitamin D in the winter.11 This deficiency can impair the immune system. 

A team at Queen Mary University of London (QMUL)  pooled data on 11,321 people from 25 separate studies to understand the effectiveness of vitamin D supplementation in preventing the common cold and flu.12 It was seen that one in every 33 people taking vitamin D would be spared from contracting the cold, contrasting to the 1 in 40 people who are spared after taking the flu vaccine. It is noted that additional supplements were more effective in those deficient in vitamin D, and there was a reduction of approximately 10% in those who had high levels of vitamin D.  

Zinc

Unlike vitamins C and D, zinc is an essential mineral that plays a crucial role in the body. It aids in the production and activation of immune cells, which helps defend the body against infections and illness. This makes it vital for maintaining a healthy immune system. It helps in wound healing as well as processing carbohydrates, fat and protein in our food. Zinc is involved in maintaining healthy skin, hair and nails. The recommended daily dose of zinc is 9.5mg for men and 7.0mg for women. Zinc can be found in a variety of food sources, including:

  • Meat: Beef, pork and lamb.
  • Poultry: Chicken and turkey
  • Seafood
  • Legume–Beans, lentils and chickpeas
  • Nuts and Seeds
  • Whole grains
  • Dairy products
  • Fortified foods such as breakfast cereals

Zinc is available in two forms - oral zinc (e.g. lozenges, tablets, syrup) and intranasal zinc (e.g. nasal sprays). It has been hypothesised that zinc lozenges can limit virus replication in nasal cells, which reduces the inflammation of the respiratory tract. It can help reduce the duration of a cold by 2-4 days when taken within 24 hours after symptoms start.13

 Zinc lozenges can cause temporary side effects such as nausea and dysgeusia (change in taste perception). However, these symptoms usually resolve once the supplementation is stopped. In addition to nausea and dysgeusia (taste changes), zinc nasal sprays have been linked to severe side effects such as anosmia  (irreversible loss of the sense of smell) and, for that reason, are not recommended.14 

Additionally, other side effects can include vomiting, loss of appetite, stomach cramps, diarrhoea, or headache, especially when taken in high doses. Long-term use can interact with medications such as antibiotics. 

Prevention

While reaching for supplements may appear as a quick and easy defence against the cold and flu, optimising their effectiveness involves following these practices:

  1. Eat a healthy nutrition-dense diet
  2. Getting 7-8 hours of sleep nightly 
  3. Washing your hands throughout the day
  4. Get the flu jab annually 
  5. Avoid touching your eyes, nose and mouth 
  6. Exercise regularly
  7. Manage your stress 

Summary

In conclusion, as winter approaches, reinforcing the importance of vitamins in supporting immune health during cold and flu season is crucial. The common cold and flu are contagious respiratory infections that can disrupt daily life and pose health risks if not addressed. 

Vitamin C, known for boosting immunity, can lead to milder symptoms and reduced cold duration with regular intake. Vitamin D, obtained from sunlight or fortified foods, regulates immune cells and prevents deficiency-related immune impairment. Zinc plays a vital role in immune cell production, and while supplements can reduce cold duration when taken early, caution is needed to avoid adverse effects. 

Beyond supplements, a holistic approach encompassing a balanced diet, sufficient sleep, exercise, stress management, and hygiene practices is essential for year-round resilience. By embracing these strategies, we can confidently face the challenges of the cold and flu season, promoting overall well-being and a strong immune response.

References

  1. Thomas M, Bomar PA. Upper respiratory tract infection. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Feb 6]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK532961/
  2. Boktor SW, Hafner JW. Influenza. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Feb 6]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK459363/
  3. Heikkinen T, Järvinen A. The common cold. The Lancet [Internet]. 2003 Jan [cited 2024 Feb 6];361(9351):51–9. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0140673603121629
  4. Huang D, Taha MS, Nocera AL, Workman AD, Amiji MM, Bleier BS. Cold exposure impairs extracellular vesicle swarm–mediated nasal antiviral immunity. Journal of Allergy and Clinical Immunology [Internet]. 2023 Feb [cited 2024 Feb 6];151(2):509-525.e8. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0091674922014233
  5. Allan GM, Arroll B. Prevention and treatment of the common cold: making sense of the evidence. CMAJ [Internet]. 2014 Feb 18 [cited 2024 Feb 6];186(3):190–9. Available from: https://www.cmaj.ca/content/186/3/190
  6. Uyeki TM, Bernstein HH, Bradley JS, Englund JA, File TM, Fry AM, et al. Clinical practice guidelines by the infectious diseases society of america: 2018 update on diagnosis, treatment, chemoprophylaxis, and institutional outbreak management of seasonal influenzaa. Clinical Infectious Diseases [Internet]. 2019 Mar 5 [cited 2024 Feb 6];68(6):e1–47. Available from: https://academic.oup.com/cid/article/68/6/e1/5251935
  7. Carr AC, Maggini S. Vitamin c and immune function. Nutrients [Internet]. 2017 Nov [cited 2024 Feb 6];9(11):1211. Available from: https://www.mdpi.com/2072-6643/9/11/1211
  8. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews [Internet]. 2013 [cited 2024 Feb 6];(1). Available from: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD000980.pub4/full
  9. Aranow C. Vitamin d and the immune system. J Investig Med [Internet]. 2011 Aug [cited 2024 Feb 6];59(6):881–6. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166406/
  10. Serrano MA. Contribution of sun exposure to the vitamin D dose received by various groups of the Spanish population. Science of The Total Environment [Internet]. 2018 Apr [cited 2024 Feb 6];619–620:545–51. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0048969717330942
  11. He CS, Aw Yong XH, Walsh NP, Gleeson M. Is there an optimal vitamin D status for immunity in athletes and military personnel? Exercise Immunology Review. 2016;22: 42–64. Available from: http://eir-isei.de/2016/eir-2016-042-article.pdf 
  12. Martineau AR, Jolliffe DA, Hooper RL, Greenberg L, Aloia JF, Bergman P, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ [Internet]. 2017 Feb 15 [cited 2024 Feb 6];i6583. Available from: https://www.bmj.com/lookup/doi/10.1136/bmj.i6583
  13. Hemilä H, Petrus EJ, Fitzgerald JT, Prasad A. Zinc acetate lozenges for treating the common cold: an individual patient data meta‐analysis. Brit J Clinical Pharma [Internet]. 2016 Nov [cited 2024 Feb 6];82(5):1393–8. Available from: https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/bcp.13057
  14. Alexander TH, Davidson TM. Intranasal zinc and anosmia: the zinc‐induced anosmia syndrome. The Laryngoscope [Internet]. 2006 Feb [cited 2024 Feb 6];116(2):217–20. Available from: https://onlinelibrary.wiley.com/doi/10.1097/01.mlg.0000191549.17796.13
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Stephanie Adimonye

MPharm, Pharmacy, University of Brighton

Stephanie Adimonye is a clinical pharmacist with four years of experience as a GPhC registered pharmacist, specialising in community and homecare (in particular total parenteral nutrition (TPN).). Currently working in a start-up online pharmacy, she combines her clinical expertise with a business oriented mindset to ensure optimal patient outcomes. Stephanie's responsibilities include formulating individualized treatment plans, administering therapy, and monitoring patients closely. Alongside her clinical work, she is undertaking the "Writing in the Sciences" online course from Stanford University, enhancing her communication skills.

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