Is Vitamin D Actually a Steroid? | Roger Seheult
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The body produces vitamin D in the skin after exposure to ultraviolet light — therefore, it is not technically a vitamin. Rather it is a fat-soluble steroid hormone, similar in structure to other hormones, such as testosterone and estrogen. Vitamin D, like other steroid hormones, can enter a cell's nucleus and regulate numerous genes. Vitamin D serves as a major regulator of immune function and may play a particularly important role in preventing respiratory tract infections. In this clip, Dr. Roger Seheult explains how vitamin D is a misnomer and how it fulfills many critical roles in the body.
Dr. Seheult: If you look at the structure of vitamin D, it is very similar to the structure of cortisol, of the structure of testosterone, of estrogen, of progesterone. And what do we know about all of these other steroid hormones? They go directly into the nucleus of the cell where they affect transcription of protein factors. And depending on the cell type, it's going to have a different effect. So already, right off the bat, you can see that vitamin D is doing something very different than what we would think of as just a vitamin where you need a cofactor to have an enzyme do A to B. It's much more nuanced than that.
And very early on, the studies on vitamin D were involving calcium, bone metabolism. And so they came up with all of these things because they didn't know what else vitamin D did, really. I mean, they had some idea, but they came up with these standards, oh, you need so much vitamin D for your bones to do whatever it needs to do and the calcium.
And so, the analogy I like to use is, like, you know, you're baking something right, and you put so much flour into the recipe. It's as if to say that's the only thing that flour is good for is this one recipe and that if you use flour for anything else, that's exactly the amount of flour that you'd have to use for any other recipe. Well, that's nonsense, of course. I mean, we know that we need a certain amount of vitamin D for proper bone metabolism. But why does that carry that that's the amount of vitamin D we need for a proper immune function? I mean, none of those things are there. And we have all of these standards about how much we need.
We'll talk a little bit about the observational studies, but vitamin D is not just a vitamin, it literally falls more into hormonal...I mean, think about Addison's disease. Addison's disease is where you have antibodies that attack the adrenal glands, this tiny little gland that sits on top of your kidneys. The purpose of that adrenal gland is to make cortisol, aldosterone, androgens. These things are essential. In fact, if people lose their adrenal glands they will die because they don't have enough cortisol. Cortisol is essential for just the regular running of the body.
And here we have this thing called vitamin D. The problem is we don't have a gland that makes vitamin D. We have the skin. So the skin through the sun, and ultraviolet radiation, which barely penetrates through the epidermis, it gets down to the dermis, where the actual starting product is. And so if you don't get enough of this, you are going to be lacking in a whole host of things.
An autoimmune disorder characterized by fatigue, gastrointestinal problems, and changes in skin color. Addison's disease occurs when the adrenal glands produce insufficient amounts of the hormones cortisol and aldosterone.
A substance whose presence is essential for the activity of an enzyme. Many minerals and vitamins are cofactors for enzymes.
A steroid hormone that participates in the body’s stress response. Cortisol is a glucocorticoid hormone produced in humans by the adrenal gland. It is released in response to stress and low blood glucose. Chronic elevated cortisol is associated with accelerated aging. It may damage the hippocampus and impair hippocampus-dependent learning and memory in humans.
Any of a group of complex proteins or conjugated proteins that are produced by living cells and act as catalyst in specific biochemical reactions.
An essential mineral present in many foods. Iron participates in many physiological functions and is a critical component of hemoglobin. Iron deficiency can cause anemia, fatigue, shortness of breath, and heart arrhythmias.
The thousands of biochemical processes that run all of the various cellular processes that produce energy. Since energy generation is so fundamental to all other processes, in some cases the word metabolism may refer more broadly to the sum of all chemical reactions in the cell.
A female sex hormone produced primarily in the ovaries. Progesterone participates in the menstrual cycle, pregnancy, and embryogenesis. It is the primary pro-gestational hormone in humans and is the dominant hormone in the second half (luteal) phase of the menstrual cycle.
A type of hormone derived from cholesterol. Steroid hormones are produced in the adrenal cortex, gonads, and placenta and have long half-lives in the body. They act as chemical messengers and regulate many physiologic processes, including the development and function of the reproductive system. Examples include estrogen, progesterone, and testosterone. The actions of the steroid hormones are mediated by the steroid hormone receptors.
The primary male sex hormone. Testosterone is critical to the maintenance of fertility and secondary sexual characteristics in males. Low testosterone levels may increase risk of developing Alzheimer’s disease.
The highest level of intake of a given nutrient likely to pose no adverse health effects for nearly all healthy people. As intake increases above the upper intake level, the risk of adverse effects increases.
A fat-soluble vitamin stored in the liver and fatty tissues. Vitamin D plays key roles in several physiological processes, such as the regulation of blood pressure, calcium homeostasis, immune function, and the regulation of cell growth. In the skin, vitamin D decreases proliferation and enhances differentiation. Vitamin D synthesis begins when 7-dehydrocholesterol, which is found primarily in the skin’s epidermal layer, reacts to ultraviolet light and converts to vitamin D. Subsequent processes convert D to calcitriol, the active form of the vitamin. Vitamin D can be obtained from dietary sources, too, such as salmon, mushrooms, and many fortified foods.
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- Vitamin D is effective for COVID-19: meta analysis of 34 studies
