Nolan Alexander (Host): This podcast is for informational purposes only and is not intended to be used as personalized medical advice.

Welcome to Be Well with Skagit Regional Health. I'm Nolan Alexander, and with me is Dr. Luis Garduno, an internal medicine physician at Skagit Regional Health as we talk about vitamin D. Doctor, how are you today?

Luis Garduno, MD: I'm doing quite well. How are you doing, Nolan?

Host: I'm doing great and I'm excited to talk about vitamin D. It's often called the Sunshine Vitamin. So why is it given that name and what role does sunlight actually play in its production?

Luis Garduno, MD: Yeah, so vitamin D is referred to the Sunshine vitamin because it's one of the few vitamins that we do not have to consume via food. We can get it through sunlight exposure. So that's the main reason why it's called Sunshine vitamin. We usually get it through ultraviolet B rays. So that's the wavelength that we do get to absorb and produce vitamin D.

Host: How does that work? Maybe without getting too deep in the weeds, but how does that actually happen in the human body?

Luis Garduno, MD: So ideally, we try to get as much sunlight exposure so the UV B rays hit our skin and then our skin does some chemical reactions in which the liver and kidneys are also part of. And these chemical reactions allows us to absorb calcium throughout our intestinal system. The higher vitamin D we get from sunlight, the higher the amount of calcium we're able to absorb and maintain healthy levels.

Host: Interesting. Doctor, what are the most important functions vitamin D performs in the body beyond bone health?

Luis Garduno, MD: Beyond bone health, vitamin D has multiple functions. Some include immune regulation, as well as cell proliferation and cardiovascular homeostasis. In the aspect of immune regulation, vitamin D does enhance production of antimicrobial proteins that help control and fight off infections, especially in the respiratory system.

In terms of cell proliferation, vitamin D regulates cell growth, promotes cellular differentiation and also inhibits abnormal cellular growth. It has been even studied in some cancer prevention, Vitamin D itself. With respect to cardiovascular homeostasis, vitamin D contributes to the inhibition of the high blood pressure hormone that we find in the body that is produced by the kidneys, and it helps maintain vascular health, as well as reduce inflammation between the vascular system.

Host: I've heard of deficiencies. How common is vitamin D deficiency in the United States? And what populations are most at-risk?

Luis Garduno, MD: Vitamin D deficiency is surprisingly common in the United States, and it does represent of the most common deficiencies involving micronutrients that we do see. Now the majority of the population are somewhat in a mild deficiency form though there are extremes in the population that are severely deficient in vitamin D. There are many factors that raises the risk of vitamin D deficiency. For example, people who tend to live in northern hemispheres where there is less sunlight exposure are at higher risk of vitamin D deficiency, especially here in the Pacific Northwest and especially during winter months. People who have higher pigmentation in their skin, so, African Americans, Hispanics, if they live in northern hemispheres, they are at even higher risk of vitamin D deficiency compared to someone with a lighter skin pigmentation. The purpose of this is because darker skin tones protect us from dangerous ultraviolet rays.

So darker skin tones are more prevalent near the equator where we do get more sunlight exposure. If those population tend to migrate to Northern hemispheres, they are increasing the risk of Vitamin D deficiency, especially if they're not either supplementing their deficiency through multivitamins or over-the-counter supplements or not getting enough vitamin D intake through their diet.

Host: So with the deficiency, what are some early signs or symptoms people might experience if they do have a vitamin D deficiency?

Luis Garduno, MD: So that is the tricky question. So as far as symptoms for vitamin D deficiency, they are very nonspecific. So it's very hard to pinpoint that any sort of symptom is related to vitamin D deficiency. But you know, there are some symptoms that can be seen in vitamin D deficiency, such as fatigue, low energy, muscle weakness as well as body aches and pains. But again, this can also be contributed to a bunch of other conditions involving health. They are vitamin D deficiency symptoms are very nonspecific, but hopefully through the guidance of your physician or health provider, they can run a variety of blood works and hopefully include vitamin D testing in there to see if you are deficient in this vitamin.

Host: Based on what you said, I've got a couple of questions here. We'll begin with this one. You talked about vitamin D levels and how that works within the body, especially the immune system. But can you explain the relationship between vitamin D levels, the immune system, especially when it comes to respiratory illnesses?

Luis Garduno, MD: So vitamin D does play a key role in regulating the immune system as well as optimizing the body's ability to fight off infection. So I briefly touched about this topic earlier, but the way that it works is that vitamin D allows our immune system through some chemical reactions within the immune systems cells itself, but it allows the production of antimicrobial peptides that help fight off viral and bacterial respiratory pathogens. One thing that we got to keep in mind of is that during winter months where flu and COVID are more prevalent, people in the Northern Hemispheres, are more vitamin D deficient during this time.

So, it is very important to supplement during these winter months, to help prevent these respiratory infections, including viral and bacterial like I mentioned. There are some studies that show that having higher levels of vitamin D are correlated with less infections. But there are more studies to be done to further clarify this issue.

Host: Okay. Well, let's drill down to maybe some specifics. What should people know about vitamin D supplementation, the dose, the frequency and any potential risks of over supplementing?

Luis Garduno, MD: Vitamin D supplementation is the most effective when it is approached with a balanced and personalized guidance through your primary care doctor or health provider. While many people, like I said, live in Northern Hemispheres, they can benefit from vitamin D supplementation through over-the-counter supplements, because they are less exposed to UVB rays that are produced by the sun versus someone living in a southern hemisphere. So as far as vitamin D supplementation, it is good to start off with anywhere from 600 international units up to 800 international units daily.

But this should be monitored, through blood work because it all depends how much sun exposure you are getting during the week or days. If someone who works outside and does get significant sun exposure, they might not need vitamin D supplementation versus someone who works inside like an office job, they might need a higher vitamin D supplementation.

So, it requires a very personalized guidance through the help of your primary care provider. So in order to prevent any vitamin D toxicity, which although rare, it can be seen and it can cause serious health issues. I think a good place to start, in general, is anywhere from 600 international units to 800 international units of vitamin D. And then get regular blood work to see if that's enough replacement of vitamin D deficiency.

If it is not, then again, with the guidance of your primary care provider, you can increase and then monitor at next visit and go from there.

Host: And Dr. Garduno, what practical daily habits would you recommend for someone living in a cloudy northern climate to stay healthy year-round?

Luis Garduno, MD: So for individuals living in a cloudy northern climate where UVB rays exposure is very limited for much of the year; intentional daily habits can play a meaningful role to maintain healthy amounts of Vitamin D. So one way to go about this is prioritizing vitamin D rich foods such as oily fish, eggs and fortified dairy products, as well as cereals can help support intake when sunlight is insufficient.

Another way to go about vitamin D supplementation is spending time outdoors whenever possible, even on overcast days and remaining physically active to further support overall health and may modestly contribute to vitamin D production during sunnier months. During fall and winter Vitamin D supplementation may be beneficial and should be considered in consultation with your primary care provider.

Host: Dr. Garduno, thank you so much for your time at insight today. We truly appreciate it.

Luis Garduno, MD: Of course. It was my pleasure, Nolan.

Host: That was Dr. Luis Garduno. For more information, go to skagitregionalhealth.org. If you enjoyed this podcast, please share it on your social channels and check out the entire podcast library for topics of interest to you. I'm Nolan Alexander, and This is Be Well with Skagit Regional Health. Thanks for listening.