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Cold, Flu, and COVID Season - Immune-Boosting Basics

Winter is just around the corner, and this year cold and flu season has been taken to a new level - cold, flu, and COVID season.

In addition to frequent hand washing, not touching your face, and proper social distancing, nutrient supplementation may provide an extra measure this winter to boost immune system function and reduce the risk of illness.

We absorb Vitamin D through direct sunlight, which is why vitamin D deficiency is common in northern climates.

Vitamin D reduces inflammation and supports a healthy gut microbiome. Vitamin D also boosts our cells’ ability to fight off microbes, including the cells lining our mouth, throat, and lungs.

Supplementing with Vitamin D has been shown to reduce your risk of developing an acute respiratory infection, and should you become ill, Vitamin D has also been shown to reduce the severity and duration of illness, and reduce complications.

• For prevention, consider 2000-5000IU Vitamin D3 daily with food.
• I routinely check Vitamin D levels in many patients and aim for a 25, OH Vitamin D level of 60-70.



Vitamin C is an immune system powerhouse. This antioxidant reduces inflammation, increases the production of white blood cells, and helps to strengthen blood vessels. Vitamin C is essential in the formation of collagen, which promotes healthy skin and muscle tissue. A lack of Vitamin C makes you more prone to illness, and should you develop a respiratory illness, Vitamin C has been shown to reduce the duration and severity, and reduce complications by protecting your own tissues from damage.

Vitamin C has been used in many hospital ICUs for the treatment of COVID-19.

• For prevention, 500-1000mg daily
• Choose a buffered form of Vitamin C for less stomach upset



Elderberry (Sambucus nigra) has widespread historical use as an anti-viral herb and has been used extensively in the prevention of influenza.

Elderberry is rich in vitamin C, antioxidants, and fiber. Research suggests that elderberry is most effective when used for prevention, or when taken early on in the course of a respiratory virus.

• For prevention, consider 500mg orally, daily (of USP standard of 17% anthocyanosides).
• Caution should be used in those with autoimmune conditions.



Zinc has a large body of research showing its strong anti-viral properties against many viruses, and zinc supplementation has been found to reduce the duration of symptoms of the common cold.

Zinc promotes antibody and white blood cell production and reduces oxidative stress. In addition, zinc has properties that fight infection directly, and zinc lozenges may reduce the risk of developing a respiratory illness.

For prevention (zinc acetate, citrate, picolinate, or glycinate), 30-60mg daily in divided doses for three months, then reduce to 15-30mg daily.

• For acute respiratory illness, begin zinc lozenges at the first sign of symptoms.



There are a number of nutraceuticals that have demonstrated immune-boosting properties. The choice of which and how many nutraceuticals to incorporate into your prevention plan will be different for each person. Factors to consider include cost, underlying chronic medical conditions, and the degree of possible virus exposure.

Subscribe to my blog for future posts highlighting other immune-boosting nutraceuticals.

Please note: Due to the novelty of COVID-19, no peer-reviewed research has been published regarding the effectiveness of dietary or lifestyle interventions for its prevention or treatment. These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Consult your healthcare provider prior to use of any nutraceutical.

Carin Nielsen, MD Integrative Medicine I use an Integrative/Functional Medicine approach with my patients to treat a variety of chronic medical conditions. During the COVID-19 pandemic, I continue to see patients from all over the state of Michigan using our secure, video-visit format. If you are interested in learning more or if you would like to schedule a consultation, please contact our office This email address is being protected from spambots. You need JavaScript enabled to view it. or 231-638-5585.

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There goes our daylight - Do you know your Vitamin D level?

Last week I had a follow-up visit with a male patient in his early 40s who had come to see me for muscle aches and decreased muscle stamina with exercise. He was having soreness on a daily basis, particularly in his upper thighs.  Laboratory workup had revealed significant Vitamin D deficiency. He reported at his follow up visit that after only 3-5 days of high-dose Vitamin D supplementation, his muscle symptoms were noticeably improved.

He was surprised to hear that I see this quite frequently, both Vitamin D deficiency and other patients with similar symptoms of muscle aches that improve when Vitamin D intake is increased. My medical practice is in Northern Michigan, and Vitamin D deficiency is quite common. I have been checking Vitamin D levels routinely on my patients for many years, and I rarely find an "optimal" level, let alone a level that isn’t deficient!


Why is your Vitamin D level important?

Did you know that Vitamin D is actually a fat-soluble hormone?  Your body produces Vitamin D in your skin when exposed to sunshine or ultraviolet light. Knowing that, it’s not surprising that north of the 45th parallel Vitamin D deficiency is quite common!

Vitamin D is necessary to absorb calcium, it helps to regulate the levels of calcium and phosphorus in the body, and together with these minerals works to maintain bone strength and integrity. The benefits of Vitamin D intake on bone health and reduction of osteoporosis is well documented by randomized controlled trials and evidence has also linked Vitamin D intake to reduced falls in the elderly.

A growing body of research suggests that Vitamin D intake may be linked to reduced risk of cancer (specifically breast, prostate and colon cancer), depression, autoimmune disease, and heart disease, although further studies are needed to verify these results.  Vitamin D deficiency has been linked to chronic muscle aches and pains, and (as described above) I have observed numerous patients with chronic diffuse muscle pain (especially in the thighs and forearms) get relief when restoring their Vitamin D levels to normal.

Do you know your Vitamin D level?

When testing your Vitamin D level, it is important to order the correct test. There are two tests for Vitamin D – 1,25(OH) Vitamin D or 25(OH) Vitamin D. 25(OH) Vitamin D is the best test as it is the best marker of overall Vitamin D status. 

A level below 30 ng/dl is considered deficient. In my practice we first look to raise levels above 30 into the “normal range”, and then look to get levels in the “optimal range” (those of you who are clients of mine know that this is a frequent topic of conversation, what is normal for one person may not be normal for another, and therefore when interpreting test results we strive for the optimal level for best health). Opinions vary as to “optimal” Vitamin D levels.  I strive to get levels to at least 48 ng/dl, as a comprehensive review of evidence from various studies found this level to be optimal for cancer prevention.

How do you raise your Vitamin D levels?

There are two types of Vitamin D: Vitamin D3 (cholecalciferol – which is the type of Vitamin D synthesized in your skin when exposed to sunlight), and Vitamin D2 (ergocalciferol – found in Vitamin D fortified foods and synthesized by plants).

Vitamin D3 is better utilized by the body than D2, and is the preferred source for supplementing. Vitamin D3 is found in eggs, organ meats, animal fat, cod liver oil, and fish.  It is also available in both liquid and capsule supplements.  If you are considering supplementing with Vitamin D speak with your physician about what dose is most appropriate for you.

Can I get too much Vitamin D?

Yes!  While Vitamin D toxicity is rare, it can happen if you over-supplement. Unlike many water-soluble vitamins, Vitamin D is fat-soluble and excess intake will store in your fatty tissues. Excess Vitamin D intake has also been linked to kidney stone formation.

For more information, or if you are interested in having your Vitamin D levels tested, contact our office at 231-638-5585 or This email address is being protected from spambots. You need JavaScript enabled to view it..





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