"I think what you're going to see is more of the urologic end points, the different cancers, especially prostate cancer," says Mark Moyad, MD, MPH.
In this interview, Mark Moyad, MD, MPH, discusses what can be expected in regard to vitamin D in urology and gives an overview of the limitations to the vitamin D blood test. Moyad is the Jenkins/Pomkempner Director of Complementary Alternative Medicine in the Department of Urology at the University of Michigan Medical Center.
The question is where do we go in 2023? If vitamin D is not working in a variety of areas, where do we go? Well, I think we should go back to the basics of vitamin D. Vitamin D, even though it's a fat-soluble vitamin—it’s absorbed better with fat—even when you take it without food, it can be absorbed. We know that to a certain extent.
A big question that's been going on for years is do I need a vitamin D blood test? It turned out in the Medicare databases and other places, it was one of the most requested and utilized blood tests over the past 5 years. The problem with the generalized screening of vitamin D is that we have learned that this blood test has some benefit, but we still don't know a lot about what it does. A lot of people would think that high levels were good. Now if you see, you can increase the risk of hypercalcemia, you can increase the risk of hypercalciuria, you can increase the risk of kidney stones. More is not necessarily better on the blood test.
I think where the blood test has merit are for individuals that may be on an osteoporosis drug, or in urology, they're on androgen deprivation—for example, they're concerned about bone loss. Another place is when someone's on a steroid like prednisone, because that can hamper the [effects] of vitamin D metabolism and calcium absorption. That still has some merit to get a blood test there. Another area is malabsorption syndrome, someone that has a situation where you don't absorb nutrients well, [like] celiac disease, ulcerative colitis, and Crohn disease.
The idea of generally screening everyone who comes in the office who's otherwise healthy, I think that's falling by the wayside, which is why no major group has recommended generalized blood screening. It's also not cheap. I think the enthusiasm for many healthy people to run out and get a vitamin D blood test based on these trials, in 2023 you're going to see it drop a little bit. You're going to see it become a little bit more specialized.
I hope there's a turning back to the dietary sources that don't get enough attention. It's a very cheap supplement. If you need to supplement, [you can use] mostly animal-based sources. Fish is a wonderful source, some mushrooms can be a wonderful source, an egg yolk is an OK source. Salmon gets talked about a lot in terms of health. I've had to go teach up in Anchorage, Alaska a lot. What we've learned is salmon and a couple of these marine fatty fish contain very high levels of vitamin D. They're very good sources. Even just a portion size of wild Alaskan salmon can be 1000 international units.
In 2023, the recommended daily allowance of vitamin D has not changed. It was established in 2011. I give this group a lot of credit, called the Institute of Medicine. What they said is for you and me and anybody who's an adult out there, the recommended daily allowance is 600 IU per day. They said if you're 71 and above, you might need a little more, which is 800, and then that should keep your test at a normal level overall.
My point in 2023 is, I have a newfound respect for vitamin D and what it can and can't do, but what I definitely respect is that it could be very easy to take too much. You’ve got to be careful and go back over your numbers with your doctor, with your dietitian, and discuss drug interactions. We're just starting to learn about potential drug interactions too, and who maybe should be on it and who should not take more. These things are all evolving in 2023. My guess is that we're going to learn more in 2023 than we did in 2022.
It's exciting. This is all the stuff that's happening in 2023. I think what you're going to see is more of the urologic end points, the different cancers, especially prostate cancer, does it have any role? We don't know. We do know that if you combine it with calcium, for example, and you take too much, it can increase the risk of kidney stones. You have to be careful and abide by the recommended daily allowance, in my opinion.
People always ask me about the vitamin D blood test and how can I look at it in a simplistic way. A good way of summarizing where we are on the vitamin D blood test is the idea that if you're worried about someone's vitamin D, if they come in at 10 or 12, or in the single digits, that's a severe deficiency. If you go back in the history books and look at children that had bone mineralization issues, this is what made vitamin D famous for bone health. That's called rickets. Where the people were at a risk of bone problems was in this very low level, which very few people have today.
The goal now is if someone has the test, and they work with their physician or health care provider, if they're at 20 or a little bit higher, a lot of people, most of the major groups, would argue that's adequate for bone health and that's adequate for overall health.
What made this all in very intriguing was in the VITAL trial (NCT01169259), the average person had a 30 before they started taking vitamin D. That's what I'm saying; America is becoming more sufficient. It's very tough to find extreme deficiency. You have to go looking for it these days. That's interesting.
What we're learning now, too, is [what happens] if you go too high with the blood test, so 50 and higher. There are a variety of sites that will show this. The Mayo Clinic, for example, shows that on their site, which is great. If you go 50 or higher, you increase the risk of high blood levels of calcium and high levels of calcium in your urine, and that can become a problem. There have been some studies to suggest that when you go this high, there's an increased risk of falls. There's an increased risk of other problems. This is a good thing for clinicians to look at in terms of what the numbers mean.
The reason why general screenings not working, though, is that this blood test is also very prognostic in the sense that as somebody becomes more heart unhealthy, as we say, or as they become generally unhealthier, regardless of if it's because of cholesterol or if it's because of hypertension or because of weight gain, it tends to drive this number down. What we're seeing about this blood test is that inflammation seems to drive this number down.
Where vitamin D got in trouble, and what I said in the Journal of Urology article,1 where the perfect storm was created with testing, was that the thought was if your vitamin D was low, and you supplemented, you could reduce your risk of a problem. We call it cause or consequence. Is low vitamin D the cause of a problem, or is it the consequence of a problem? What we've learned is that, in some cases it may be the cause, but in a lot of cases is the consequence of a problem. Even if you raise it very high, it doesn't change that.
For the past few years, there's been a thought that if you take vitamin D, it can help with weight loss, it can help reduce your blood pressure, it might have an effect in a variety of areas, [like] cognition. That has not turned out to be true. Part of the reason that it was a problem is that the blood test is imperfect. If you're dealing with a lot of comorbidities, and a lot of health problems, it naturally drives that blood level down.
Part of the reason people were so excited about COVID and taking vitamin D is that there were early studies showing that people with very low levels of vitamin D had a higher risk of severe COVID. The thought was maybe they should supplement. It's turning out that a lot of studies are showing that the reason they had a higher risk for COVID was other reasons, because they were older, because of obesity, because they had kidney disease. They had a lot of other pre-existing conditions that were bringing that test down. We call it a negative acute phase reactant. Just because you bring the test up with a pill doesn't mean you're going to solve the problem.
It's been a real eye opener about not just what vitamin D can or can't do, but also about the limitations of this blood test. We know in a very select number of people, it may provide a benefit, but the idea of generally screening everyone right now is not only costly, but it's not recognizing the fact that this comes with a lot of limitations. If you're dealing with a lot of health problems, the chances that your vitamin D is going to be low is very high, simply because it drives that number down. In urology, a classic example of that all the time is, you might see someone with low testosterone, they have a low vitamin D level. But maybe that's just because in some cases, they're carrying a lot of weight that has driven down the testosterone level, and it's also driven down the vitamin D level.
This is all the stuff we're learning about in the past year or 2, which is incredible. It's incredible. And I love it. I hope that we'll learn this next year whether it has any impact in prostate cancer, good or bad. I'm hopeful that we'll have that answer in 2023.
1. Moyad MA. Vitamin D and the vital need for more VITALs: seeking causation amidst escalating association, inflammation, and supplementation. J Urol. 2023;209(1):29-31. doi:10.1097/JU.0000000000003036