For maintaining healthy bones and muscles, vitamin D is an essential part of people’s diet. Vitamin D referred to as calciferol can be obtained through food, sun exposure, and supplements and is one of the only fat-soluble vitamins that can be both made by our bodies and be found in food sources. Because of these widely known benefits, many people have decided to take upon these vitamin D benefits and boost their intake through the best vitamin D supplements out there. But could too much vitamin D cause negative side effects? Is it possible that vitamin D is too good to be true?

In response, we’re going to explore vitamin D in more detail, looking into the research behind this unusual vitamin and learn about the best ways to take vitamin D supplements, including the recommended vitamin D intake, what causes vitamin D deficiency, can it really prevent other health conditions and what happens when you take too much vitamin D.

Vitamin D As Both Nutrient And Hormone

Vitamin D is remarkable because it’s both a nutrient and hormone. It’s not entirely a vitamin but rather a group of steroid molecules that are generated from exposure to light and food. Our bodies both produce and need this vitamin to absorb calcium, which assists in normal bone mineralization and prevents involuntary muscle contractions. As a nutrient, our bodies are able to metabolize and store this vitamin in our bodies. It also acts as a prohormone or a precursor to hormone production. When Vitamin D enters our system, it can produce multiple types of hormones due to the various chemical reactions our metabolism goes through, including:

Cholecalciferol: Known as vitamin D3, this vitamin assists in calcium homeostasis and acts as a steroid hormone by interacting with the vitamin D receptors within our metabolism. This version of vitamin D helps many people maintain elderly bone density and lowers the risk of fractures.

Ergocalciferol: Known as vitamin D2, this vitamin forms from plant-derived materials that are exposed to sunlight, including mushrooms. Our bodies do not naturally produce vitamin D2 but are often prescribed as a supplement for conditions such as hypoparathyroidism and rickets.

Calcidiol: When our bodies metabolize vitamin D3, the liver goes through the process of hydroxylation, turning it into the enzyme calcidiol, binding with the vitamin D receptors within our blood to mineralize our bones.

Calcitriol: Calcidiol can be further converted into calcitriol, an active hormone of vitamin D that also binds with the vitamin D receptors. It helps increase blood calcium, which assists with gene expression to help improve bone density and muscle contractions.

All of these versions, primarily concerned with vitamin D3 and D2, all assist with the body’s metabolism in various ways. Cholecalciferol is the reaction that occurs when our bodies first interact with Vitamin D, and from there, our livers convert the reaction to calcidiol. The kidneys convert the substance after that to calcitriol, the active hormone that binds to our receptors and helps fortify our bones and muscles.

How Vitamin D Transfers Into Our Blood

When our bodies take in vitamin D, our vitamin D receptors help transcribe our gene expression, containing hormone-binding and DNA-binding domains. These components work with our DNA to provide the essential instructions for utilizing the vitamin D benefits within our system. As for the physiological effects of vitamin D, the effects can most often be found in the intestines. This hormone stimulates the formation of phosphate and magnesium ions and assists the intestines in absorbing calcium. Vitamin D, in these cases, works to increase the expression of our proteins that help transport calcium, phosphate, and magnesium into our blood. It goes through a specific process to provide these benefits, including:

The Intestines: The lumen, or inside layer of the intestine, works with the proteins produced by the presence of vitamin D, or calcitriol, across to the epithelial cells.

Epithelial Cells: Our epithelial cells, located along the outer membrane of the intestines, help transfer those proteins into our bloodstream. Calcium is transferred alongside these proteins through calbindin transporters and makes vitamin D absorption easier.

Bloodstream: From there, our bloodstream help carries these vitamins and minerals throughout our body and delivers these nutrients and hormones to specific areas, including our bones, muscles, and other areas of the body.

However, it isn’t just the intestines that deliver the benefits of vitamin D. In fact, vitamin D receptors can be found throughout all cells in our body. Because of this, vitamin D benefits may also have a bigger physiological effect on the growth and differentiation of many types of cells and may not just contribute to mineral homeostasis and bone function.

Studies in Vitamin D and Its Health Conditions

Vitamin D has been commonly associated with various diseases and conditions, often due to how vitamin D receptors are present within almost all cells in the body. Its role in gene expression and regulation means that vitamin D also impacts brain development and function, diabetes development, cardiovascular disease, and cancer. Because vitamin D is a precursor hormone that regulates gene expression, the role that vitamin D has in our health is ever-complex and evolving. Below, we’ll look at multiple studies on the effects of vitamin D benefits and its various health conditions:

Vitamin D and Bone Health: Because of its ability to carry calcium and other minerals throughout the system, it’s considered one of the best ways to protect people’s bone health. Many studies often cited for its benefits focus on its ability to maintain cellular function, promote mineralization, and maintain calcium and phosphorus concentrations. From these benefits, it’s most often recommended for those at higher risk of developing a vitamin D deficiency or at a higher risk of developing conditions such as osteoporosis.

However, some studies looking into the best vitamin D supplements for preventing falls and fractures show that it doesn’t prevent the risk. The study observed the effects of vitamin D supplements on how it boosts bone mineral density and its ability to prevent bone fractures. These studies concluded that the best vitamin D supplements didn’t affect the rate of falls and fractures among those with bone conditions or have a higher risk of bone fractures, such as the elderly. However, organizations such as the National Osteoporosis Society concluded that despite the risks, it does not change the recommended vitamin D intake for those at risk for osteoporosis and other bone conditions.

Cholesterol Levels and Vitamin D: Women going through post-menopause often suffer from poor lipid profiles, increasing bad cholesterol and triglycerides. However, recent studies from the Women’s Health Initiative trials showed that women supplementing with the best vitamin D supplements over the course of two years had not only higher levels of vitamin D in their blood but also experienced better lipid profiles. Because of the introduction of better lipid levels with calcium and vitamin D intake, the study also concluded that the risk of hip fractures among women was decreased compared to those under the placebo effect.

Heart Disease and Vitamin D: Those concerned about the effects of heart disease should be aware that although vitamin D tablets can increase bone density, they may not protect people against cardiovascular disease. A meta-analysis was performed on randomized clinical trials that included more than 83,000 participants. The previous studies cited that the effects that vitamin D has on nutrient transportation and gene expression that could decrease the risk of heart disease among men and women. However, the meta-analysis concluded that vitamin D supplementation doesn’t provide any protection against cardiovascular disease due to the measures used to perform the trials.

Vitamin D and Arthritis: When it comes to connecting vitamin D supplementation with arthritis, some research has shown that people with lower levels of vitamin D are associated with a higher risk of developing rheumatoid arthritis. According to this study, vitamin D plays a huge role in regulating the immune system and thus can play a huge role in the development of autoimmune disorders. Due to this reasoning, some participants experienced less inflammation throughout the joints when increasing their vitamin D levels. However, because the studies connecting these two factors remain inconsistent, it cannot be concluded.

Diabetes and Vitamin D: People wishing to prevent the onset of type 2 diabetes may be disappointed, as vitamin D supplements in recent studies do not reduce the risk; according to some studies, the introduction of the best vitamin D supplements had no difference in those at risk of developing type 2 diabetes when compared to placebo. However, some studies in previous cases believe that vitamin D may be able to increase insulin sensitivity for those with type 2 diabetes, thus reducing the risk of insulin resistance associated with this condition. Within these cases, type 2 diabetes usually occurs alongside the presence of a vitamin D deficiency, which contributes to numerous other health problems, including cancer and osteoporosis. Thus, many of these cases remain inconclusive.

Vitamin D and Asthma/Allergies: When comparing the rates of vitamin D levels with those who have asthma and allergic conditions, many of the findings remain inconclusive, as the connections between these two factors remain vague. One study reports that the best vitamin D supplements can be used as an adjective treatment for managing asthma when considering its other vitamin D benefits. However, the results of the study are concluded as being unreliable due to the inability to define its role in asthma development. Other studies also support the statement, as vitamin D3 supplementation did not support its use for severe asthma in children and other allergic conditions.

Autism and Vitamin D: Because of the impact vitamin D has on gene expression, many studies have reported that inadequate levels of vitamin D in pregnant women could potentially increase the risk of autism in children. Studies from the University of Queensland report that mothers with a vitamin D deficiency could increase the testosterone levels of male fetuses, impacting proper neurodevelopment. However, some studies also prematurely conclude that an increase in vitamin D levels may also increase the risk of neurodevelopmental disorders. However, in these cases, the majority of studies conclude that the role of vitamin D needs to be better defined to evaluate if it can reduce the impact of autism spectrum disorder.

What Happens When You Take Too Much Vitamin D?

Vitamin D has been reported to have many benefits to our metabolism, bones, and muscles, but for those interested in taking vitamin D tablets, there is the potential to experience vitamin D toxicity resulting from large doses. Vitamin D toxicity is created when the body isn’t able to regulate the amount of vitamin D within the bloodstream. It causes a large buildup of calcium in the blood, known as hypercalcemia. Hypercalcemia causes frequent urination, nausea, vomiting, and weakness. This condition can progress to kidney problems and bone pain, causing the formation of calcium stones.

Most often, higher recommended vitamin D intake is for those who suffer from vitamin D deficiency. However, these higher doses are often used under the care of your GP or physician for a specific amount of time. If you believe you may have vitamin D deficiency, then your blood levels should be monitored to prevent the risk of too much vitamin D.

The Recommended Vitamin D Intake In the UK

According to NHS, the recommended daily dose of vitamin D for babies ages one year needs between 8.5 to 10 micrograms of vitamin D a day. Children beyond the age and adults of one need ten micrograms a day, especially for those who are pregnant, breastfeeding, and have a vitamin D deficiency. However, the NHS recommends that for those who don’t have a vitamin D deficiency, vitamin D should be received from the diet during the autumn and winter months, while throughout the early spring to summer months, people can receive their daily dose through sunlight. If you’re interested in taking vitamin D tablets and have a risk of developing a vitamin D deficiency, then you should speak with your GP for more information.