Zinc and vitamin D and their importance in the prevention and treatment of the common cold
A cold is a common and contagious virus that normally lasts around a week. If a person has poor resistance, however, complications such as sinus infections, ear infections, and pneumonia may follow. Colds cause a substantial number of sick days and represent a huge socioeconomic burden to society, but zinc supplementation seems to be able to reduce the number of sick days. Just remember to get enough vitamin D also because of interactions between the two nutrients.
There are more than 100 different viruses that can cause a cold. The virus is transmitted through the spread of airborne droplets when people cough or sneeze, or it can be passed on through skin contact or by touching surfaces. Typical symptoms are sore throat, runny nose, nasal congestion, tiredness, and feeling indisposed. Colds are normally mild and last around a week. However, if the immune defense is not functioning properly, bacteria from the natural microflora can spread to the sinuses, the middle ear, or the lungs and cause complicated infections. People normally catch a cold 2-3 times per year and typically during the winter months, but an optimal immune system should be able to prevent this.
Zinc supplements reduce the number of sick days
It has been common practice for years to recommend zinc supplements to prevent and treat colds. However, the scientific evidence to support the effect of zinc supplementation has been scarce, but researchers have looked closer at it and published a study in the Cochrane Database of Systematic Reviews. They analyzed a number of randomized controlled studies (RCT) from Medline, Embase, and other databases to see if zinc supplements could help prevent and treat colds and other respiratory infections. Studies where zinc was administered together with other vitamins, minerals, and herbs were excluded.
The new analysis includes 34 studies with a total of 8,526 participants from several countries. Fifteen studies look at prevention, while the remaining 19 studies look at treatment. A total of 22 studies were done with adults, and 12 studies were carried out on children. The result showed that high-dosed zinc supplementation has limited or no effect when it comes to preventing a cold. However, it may reduce the number of sick days in those who have already contracted a cold. An older Finnish meta-analysis showed that cold-ridden people who took high doses of zinc (80-92 mg per day) got well several days sooner than non-supplemented people with colds. It is important to choose zinc preparations with good absorption. Also, avoid taking high doses of zinc for prolonged periods of time as this may cause a deficiency of iron and copper because of the antagonistic effect.
Zinc’s role in the immune system
Zinc is important for the innate immune defense that fights most germs without causing symptoms. It is also important for the adaptive immune defense that develops after birth. In this defense system, activated T cells provide the best immunity against virus infections. Zinc works in close relation with vitamin D that also has different functions in the immune system.
Zinc helps cells absorb and utilize vitamin D, and vitamin D is important for the zinc uptake in the intestine and for several zinc-dependent functions. Therefore, if there is a deficiency of one or both nutrients, it can lead to a host of different conditions, including respiratory diseases.
Cold and respiratory ailments typically circulate during the winter period, which is when we typically have too little of the nutrient in the blood because the summer sun is our main source.
Vitamin D supplementation in the right doses prevents acute respiratory infections
A meta-analysis from Queen Mary University in London that is based on data from around 25 clinical studies with 11,000 people from 14 countries has shown conflicting results of vitamin D supplementation taken to prevent acute respiratory infections. The researchers finally found discovered why the outcome of the studies differed. Those people who already had low vitamin D levels in their blood benefited the most from taking vitamin D. In other words, there is not much point in taking vitamin D if you are not deficient, or taking doses that are too small to optimize blood levels of the nutrient. The meta-analysis is published in BMJ.
References:
Daryl Nault et al. Zinc for prevention and treatment of the common cold. The Cochrane Database of Systematic Reviews. 2024
Ashton Amos, Mohammed S. Razzaque. Zinc and its role in vitamin D function. Current Research in Physiology. 2022
William B. Grant. A Narrative Review of the Evidence for Variations in Serum 25-Hydroxyvitamin D Concentration Thresholds for Optimal Health. Nutrients 2022
Martineau Adrian et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. The BMJ 2017
University of Helsinki. Zink acetate lozenges may increase the recovery rate from the common cold by three-fold. ScienceDaily 2017
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