Like a juicy orange on a sunny day, vitamins C and D make a fantastic duo. Each nutrient serves many functions in the body; from supporting respiratory and cardiovascular health, to managing anxiety, and maximizing immune function—these vitamins are truly a powerhouse team. While it is always important to make a conscious effort to get these nutrients in our bodies, no time may be more vital than the winter months. Colds and flus are circulating, gloomy weather can really impact our mood,¹ and there are gatherings to organize and enjoy.

Unlike most mammals, humans cannot synthesize vitamin C.² This means we must acquire the vitamin through the diet and by supplementing. Deficiency is common among elderly populations and can lead to scurvy. Even today, scurvy—the sailors’ disease of the 1700s—can develop without sufficient vitamin C consumption.³

Vitamin D is the sunshine vitamin. UVB rays are absorbed through our skin and go through a process to become an active form of vitamin D, but during the winter months, we are at a higher risk of deficiency of this vital nutrient. Other factors that can affect our vitamin D levels include latitude, skin pigmentation, and sunblock. Deficiency is extremely common worldwide.⁴

Immuni-team

Vitamin C is perhaps most famous for its role in immune functioning—mom was right when she told us to take vitamin C when we felt a cold coming on! When a pathogen is present in the body, our immune cells fuel up on vitamin C, making it especially important to increase vitamin C intake when we’re sick. This antioxidant nutrient also helps protect our immune cells from oxidative damage as they fight viruses and bacteria.^{5 6}

Supporting the fight against infection alongside vitamin C is vitamin D. There are vitamin D receptors in almost every immune cell, and the sunshine vitamin provides comprehensive immune system support, from fighting colds and flus, to maintaining upper respiratory health, to alleviating asthma to reducing the risk of autoimmune diseases.⁷ Throughout the COVID-19 pandemic, multiple studies have assessed the link between vitamin D levels and the disease. Early on in the pandemic, a correlation was observed between vitamin D deficiency and higher risk of mortality and more severe symptoms of COVID-19,⁸ and research continues to confirm this link.

Bye, bye blues

While you’re shopping, cleaning, preparing for big feasts and family gatherings, the vitamin C and D you take to support your immune system will also help keep anxiety and winter blues at bay.

In one study, researchers looked at the impact of a single dose of 1,000 mg of vitamin C on anxiety. The participants, graduate students with high levels of anxiety, reported lower levels of anxiety after taking the vitamin. Even more studies have looked at the impact of regular supplementation on mood and found a correlation between supplementing and improved symptoms of anxiety and depression.⁹

The winter months can be gloomy, and a turn in the weather and less access to time in the sun can lead to seasonal affective disorder (SAD). In one study investigating the relationship between vitamin D levels and depressive symptoms, researchers concluded that there was a correlation between low vitamin D levels and SAD. Additionally, the researchers noted that high-dose supplementation may be beneficial for improving mood and SAD symptoms.¹⁰

The trouble with sugar

Here come the sweets! Tis’ the season of pies and home-baked goods, and while they are most definitely tempting, sugary sweets can also interfere with vitamin C and D levels.

Sugar can cause vitamin D to break down and impede the body’s ability to synthesize it, lowering vitamin D levels and putting us at risk for deficiency. This is especially not ideal during the winter when risk of deficiency is already high. Low levels of vitamin D also exacerbate the inflammatory effects of sugar.^{11 12}

Because the two are molecularly similar, sugar also competes with vitamin C for uptake. Both sugar and vitamin C use the same transporters to reach cells, which means that sugar can slow down or altogether stop the uptake and use of vitamin C in our cells.^{13 14}

Studies have shown that vitamin C doses of 500-1,000 mg/day help maintain healthy levels to support all of its functions in the body. Optimal levels of vitamin D are between 40 and 60 ng/mL. To reach these levels, health practitioners often recommend 5,000 IU/day (a 25-hydroxy-vitamin D test can determine your levels).^{15 16} Whether it’s optimizing immunity or supporting mental wellness (or both!), vitamins C and D are the key to winter wellness!

Keep the Kiddos Healthy, Too!

Vitamin C and D are two supplements that are known to be safe for children. Nutritionists recommend supplementing the youngest members of our families with vitamin D to support bone health, lung health, and immune function. Specially formulated supplements are available to ensure babies and toddlers receive an appropriate dosage. For school-aged children, support their immune systems with vitamin D and C throughout the school year. If getting your kids to eat their veggies, play outside in the sunshine, or take vitamins is sometimes a struggle (life happens!), consider a multivitamin. Choosing a multivitamin that prioritizes vitamins C and D can support kids optimal wellbeing, especially through the winter months.^{17 18}

References

1. Jorde R, Sneve M, Figenschau Y, Svartberg J, Waterloo K. Effects of vitamin d supplementation on symptoms of depression in overweight and obese subjects: Randomized double blind trial. Journal of Internal Medicine. 2008;264(6):599-609. doi:10.1111/j.1365-2796.2008.02008.x
2. Vitamin C. Linus Pauling Institute. https://lpi.oregonstate.edu/mic/vitamins/vitamin-C. Published January 1, 2021. Accessed July 2021.
3. Callus CA, Vella S, Ferry P. Scurvy is Back. Nutr Metab Insights. 2018;11:1178638818809097. Published 2018 Nov 21. doi:10.1177/1178638818809097
4. Aranow C. Vitamin d and the immune system. Journal of Investigative Medicine. 2011;59(6):881-886. doi:10.2310/jim.0b013e31821b8755
5. Immunity in depth. Linus Pauling Institute. https://lpi.oregonstate.edu/mic/health-disease/immunity#reference55. Published January 1, 2021. Accessed July 2021.
6. Vitamin C. Linus Pauling Institute. https://lpi.oregonstate.edu/mic/vitamins/vitamin-C. Published January 1, 2021. Accessed July 2021.
7. Hwij, Ghaleb Mohd Faisal Abu, and Samer Abdullatif Ali. "Role of Vitamin D on Body Systems." Middle East Journal of Family Medicine 19.5 (2021).
8. Bae M, Kim H. The role of Vitamin C, Vitamin D, and selenium in immune system against COVID-19. Molecules. 2020;25(22):5346. doi:10.3390/molecules25225346
9. Moritz B, Schwarzbold ML, Guarnieri R, Diaz AP, Rodrigues AL, Dafre AL. Effects of ascorbic acid on anxiety state and affect in a non-clinical sample. Acta Neurobiologiae Experimentalis. 2017;77(4):362-372. doi:10.21307/ane-2017-068
10. Jorde R, Sneve M, Figenschau Y, Svartberg J, Waterloo K. Effects of vitamin d supplementation on symptoms of depression in overweight and obese subjects: Randomized double blind trial. Journal of Internal Medicine. 2008;264(6):599-609. doi:10.1111/j.1365-2796.2008.02008.x
11. Ballantyne //  by DS, Ballantyne DS, Ballantyne ADS, speaker A-winning public. 5 nutrients you're DEFICIENT in... if you eat too much sugar. The Paleo Mom. https://www.thepaleomom.com/5-nutrients-youre-deficient-in-if-you-eat-t…. Published June 19, 2019. Accessed August 24, 2021.
12. Roth CL, Elfers CT, Figlewicz DP, et al. Vitamin d deficiency in obese rats exacerbates nonalcoholic fatty liver disease and increases hepatic resistin and toll-like receptor activation. Hepatology. 2012;55(4):1103-1111. doi:10.1002/hep.24737
13. Ballantyne //  by DS, Ballantyne DS, Ballantyne ADS, speaker A-winning public. 5 nutrients you're DEFICIENT in... if you eat too much sugar. The Paleo Mom. https://www.thepaleomom.com/5-nutrients-youre-deficient-in-if-you-eat-t…. Published June 19, 2019. Accessed August 24, 2021
14. Clemens Z. Vitamin c and disease: Insights from the evolutionary perspective. Journal of Evolution and Health. 2013;1(1). doi:10.15310/2334-3591.1030
15. Jorde R, Sneve M, Figenschau Y, Svartberg J, Waterloo K. Effects of vitamin d supplementation on symptoms of depression in overweight and obese subjects: Randomized double blind trial. Journal of Internal Medicine. 2008;264(6):599-609. doi:10.1111/j.1365-2796.2008.02008.x
16. de Oliveira IJ, de Souza VV, Motta V, Da-Silva SL. Effects of Oral Vitamin C Supplementation on Anxiety in Students: A Double-Blind, Randomized, Placebo-Controlled Trial. Pak J Biol Sci. 2015;18(1):11-18. doi:10.3923/pjbs.2015.11.18
17. To get sick less often, try these inexpensive nutrients. Green Valley Natural Solutions. https://greenvalleynaturalsolutions.com/to-get-sick-less-often-try-thes…. Published November 2, 2020. Accessed July 2021.
18. Team CH. The benefits of vitamin C: Why your child needs it. Cleveland Clinic. https://health.clevelandclinic.org/the-benefits-of-vitamin-c-why-your-c…. Published August 24, 2020. Accessed July 2021.