When you get sick do you seek specific nutrients or foods to aid healing? In this article I talk about nutrition when you are sick. I cover three nutrients that are commonly supplemented, including vitamin C, zinc and vitamin D. I also discuss the use of honey when you have a cold.
Note: The guidelines in this post are generalized. You may have unique or different needs for nutrition supplementation. Always check with your healthcare provider for individualized recommendations.
Research Findings for Use of Vitamin C
There has been a lot of research about vitamin C and its effects on the common cold. Researchers have looked at how it might help prevent and reduce the length and severity of the common cold. Coming up with a conclusion seems more nuanced than expected. A large systematic review by the Cochrane Library was completed in 2010 and researchers concluded that taking vitamin C reduced both overall duration of the common cold by 8%. Severity was also reduced for adults and children. These findings were not the same when vitamin C was taken after the individuals were already sick. However, several commenters provided critical feedback about the outcomes of the review, questioning the statistical analyses and the studies that were used/included in the review.2
Overall most scientists agree that people who participate in intense athletics or are exposed to cold weather often, like marathon runners and those that ski, benefit from vitamin C supplementation. Additionally, those that smoke also benefit from using vitamin C supplements. People that smoke need at least 35 mg of additional vitamin C daily compared to the regular RDA for their age group.3
Vitamin C Needs
According to the RDA (recommended dietary allowance) Adults 19 years old and up need 75 to 120 mg of vitamin C daily. Needs are dependent on gender and pregnancy/lactation status. You can view your specific needs here.
Tolerable upper intake level for vitamin C is 2,000 mg/day for adults that are 19 years old and older.3
Generally, 70% to 90% of vitamin C is absorbed. When an individual takes more than 1,000 mg of vitamin C, absorption decreases to 50%.3
Too much vitamin C can cause stomach upset, including diarrhea, nausea and cramping. As vitamin C aids the absorption of iron, individuals with iron absorption disorders (such as hemochromatosis) are at risk for absorbing too much iron with high doses of vitamin C supplementation.
Additionally, too much vitamin C may actually decrease the immune system’s ability to fight infection. Too much of a good thing can be bad.3
The Bottomline About Vitamin C
Taking vitamin C after getting sick does not seem to be helpful. But when vitamin C is taken on a daily basis prior to getting sick, duration and severity of illness may be moderately decreased.
If you take a daily multivitamin, it likely already has 100% of your vitamin C needs. If not, you may consider taking a supplement that meets your RDA. Be mindful to not take more than tolerable upper intake level to avoid side effects.
Keep in mind that many foods are a great source of vitamin C. This includes bell peppers, citrus fruits, berries, tomatoes, broccoli, kiwi, etc.
Research Findings for use of Zinc
A systematic review about using zinc lozenges was completed in 2011. Zinc was studied because individuals that have a zinc deficiency have increased risk for infections. These individuals obviously benefit from having zinc supplementation. But researchers wanted to know if a zinc supplement during a common cold is helpful for individuals that are not deficient in zinc.
When reviewing the research, the scientists found that when participants in several studies took more than 75 mg of zinc, their colds were less severe. Additionally, findings from other studies showed that the duration of colds was reduced by 20-42% when taking zinc.4
The RDA (recommended dietary allowance) for zinc ranges from 8 to 12 mg/day for adults that are 19 years or older and the tolerable upper intake level for zinc is 40 mg per day for the same age group. You can see what zinc recommendations are for you here.
The type of zinc supplement that you take can affect the amount of zinc your body is able to absorb. If your zinc lozenge is made with citrate, tartrate or glycine, these substances can bind to some of the zinc and decrease absorption. For example, 61% of the zinc in zinc citrate supplements is absorbed. Likewise 50% of zinc in the form of zinc oxide is absorbed.
Additionally, elemental iron supplements can inhibit zinc absorption and should be taken 2 hours apart from one another.4,5
During the studies that were included in the review, some individuals found that taking zinc supplementation caused a bad taste in their mouths. Constipation was also experienced. Other side effects with long term zinc supplementation can include dizziness, reduced appetite, nausea and/or vomiting and headaches.
If you take more than 50 mg of zinc for several weeks or more, a copper deficiency can occur. Additionally, excess zinc can lower your HDL (the good cholesterol) and can cause reduced immune function. Of course, reducing our immune function is the very thing we want to avoid.4,5
The Bottomline About Zinc
More research is needed to determine what kind of zinc and what dosage is best for use during common colds.
The information we have about zinc supplementation seems contradictory. As noted above, scientists found that taking anything less than 75 mg/day did not make a difference in the length or severity of the common cold, but the tolerable upper intake level is at 40 mg for adults and taking more than 50 mg may cause negative side effects.
The balance between benefiting from zinc supplementation and avoiding adverse side effects is in limiting how long you take the zinc supplements. Most colds do not last longer than 2 weeks and this is likely a safe cut off for extra zinc intake.
I think that taking 75 mg, or just over 75 mg of zinc daily at the beginning of a cold is safe and is worth trying if you are interested in doing so. When the cold resolves, stop taking the zinc supplement, or at least reduce to the RDA for you. When choosing a zinc supplement, keep in mind that zinc oxide and zinc with citrate, tartrate and glycine in the ingredients will have some reduced absorption.
Research Findings for use of Vitamin D
Vitamin D in doses of 400 IU and up to 2,000 IU per day helps prevent respiratory infections and decreases complications related to respiratory infections.
Healthy individuals benefit from vitamin D supplementation, but those who are deficient in vitamin D and those who were not already taking vitamin D supplements receive the most benefit.1
Vitamin D Needs
The RDA for vitamin D for adults is 600 IU per day for those that are 19 to 70 years old. The RDA for anyone over the age of 70 is 800 IU per day. The tolerable upper intake level for vitamin D is 4,000 IU per day. View your specific needs here.6
As vitamin D is a fat soluble vitamin, the vitamin D we get from foods and supplements is better absorbed with fats in the foods we eat.
Vitamin D supplements come in the form of D2 or D3. While both forms of vitamin D are well absorbed, vitamin D3 raises blood levels of vitamin D more and maintains increased levels longer.6
As vitamin D increases calcium absorption, too much vitamin D can cause our bodies to absorb too much calcium. Negative outcomes of excess vitamin D may include kidney stones, nausea and vomiting, muscle weakness, irregular heart beats, calcium deposits in our cardiovascular system and even death.6
The Bottomline About Vitamin D
More research is needed to determine the best dosage for vitamin D when considering its affects on prevention of the common cold and respiratory infections.
In general, for adults who are not deficient in vitamin D, supplementing with at least 400 IU of vitamin D daily can help prevent upper respiratory infections. Many daily multivitamins already have 400 IU of vitamin D, so you may already be receiving this amount if you take a multivitamin.
If you do have a vitamin D deficiency, supplementation is necessary. Work with your health care provider to determine the amount of supplementation that is right for you.
Research Findings for use of Honey
The sweetness of honey is just one of its many good traits. The benefits of honey extend to our health, including when we get sick.
Researchers that did a systematic review in 2021 found that honey has been found to help improve coughing due to upper respiratory infections. The benefits include reduced severity and frequency of coughing. In fact, scientists find that honey works better than using diphenhydramine (antihistamine allergy medications) for a cough.
When health care providers recommend honey for viral upper respiratory infection symptoms, they may also reduce unnecessary prescriptions for antibiotics.7
Some participants in the studies reported mild nausea. Honey is otherwise safe for anyone over the age of one year, and for those who do not have allergies to honey. For individuals with diabetes, keep in mind that one tablespoon of honey has 17 gm of carbohydrate, and one teaspoon has about 6 gm of carbohydrate.
The Bottomline About Honey
Honey is very accessible and affordable. It is considered safe to use for anyone over the age of one year, and for those who do not have allergies to honey. As honey is like a sweet treat and enjoyed by many, it is also quite easy to give to children and adults alike.
When you have a cough, you can take 1/2 to 1 tsp of honey as needed to help reduce both the frequency and severity of your coughing
Last Words on Nutrition When you are Sick
People often look to nutrition to aid in healing when they are sick. I looked at the use of vitamin C, zinc, vitamin D and honey in this article.
Typically, we will see the most benefit from nutrient supplementation for those with a cold or upper respiratory infection when a person is already deficient in the nutrient. However, for the general population without deficiency, supplementing vitamin C, zinc and vitamin D may help decrease severity and length of illness. Additionally, honey has been found to be helpful for those with a cough from an upper respiratory infection.
When choosing to supplement nutrients, make sure you follow the recommended dietary allowance and tolerable upper intake levels. Any supplements or multivitamins you already take may have some of the nutrient you are looking to supplement; take these into consideration so that you do not take too much.
It is also important to check that any supplements you take do not interact or compete with medications you are taking.
And as always, ask your health care provider if you have any questions or are uncertain about taking nutrient supplements. Doctors should be notified of any supplements you are taking long term.
If you would like to read more about guidelines on using nutrient supplements, which also provides a list of resources you can use to determine which supplements are safe to use, check out my article Are Supplements Good for You?
- M. Rondanelli et al, Self-Care for Common Colds: The Pivotal Role of Vitamin D, Vitamin C, Zinc, and Echinacea in Three Main Immune Interactive Clusters (Physical Barriers, Innate and Adaptive Immunity) Involved during an Episode of Common Colds-Practical Advice on Dosages and on the Time to Take These Nutrients/Botanicals in order to Prevent or Treat Common Colds, Evidence-Based Complementary and Alternative Medicine, 2018.
- H. Hemila, E. Chalker, and B. Douglas, Vitamin C for preventing and treating the common cold, The Cochrane Library, 2010.
- (2023, February 28). National Institutes of Health, Office of Dietary Supplements. Vitamin C. https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/.
- H. Hemila. Zinc Lozenges May Shorten the Duration of Colds: A Systematic Review. The Open Respiratory Medicine Journal. 2011.
- (2023, February 28). National Institutes of Health, Office of Dietary Supplements. Zinc. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/.
- (2023, February 28). National Institutes of Health, Office of Dietary Supplements. Vitamin D. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/.
- H. Abuelgasim, C. Albury, J. Lee. Effectiveness of honey for symptomatic relief in upper respiratory tract infections: A systematic review and meta-analysis. BMJ Evidence-Based Medicine. 2021.