The Science of Vitamin D: Exploring the Facts and Fallacies of Supplementation

Recently, a growing emphasis has been on supplementing our diets with vitamin D. However, the consequences of this trend have led to a nation facing increased weight, poor health, and fatigue. Understanding the true nature of vitamin D, its effects on the body, and the potential risks associated with supplementation is crucial. 

Vitamin D: A Hormone, Not a Vitamin:

Contrary to its classification as a vitamin, vitamin D should not be considered a vitamin due to its ability to be synthesized in adequate amounts by the body through exposure to sunlight and a proper diet. The traditional definition of a vitamin states that it is an organic compound essential for normal growth and nutrition, obtained in small quantities from the diet. Vitamin D’s role as a hormone produced by the kidneys, regulating blood calcium concentration and impacting the immune system, aligns more with the functions of other hormones in the body.

Sunlight and the Body’s Vitamin D Production:

While a small portion of the body’s vitamin D requirements can be obtained from food sources such as dairy products and oily fish, the majority is synthesized internally. When sunlight interacts with the skin, a chemical reaction occurs, resulting in the production of cholecalciferol. This compound is then converted to calcidiol in the liver and further transformed into calcitriol, the active form of the hormone, by the kidneys.

Vitamin D’s Broad Influence:

Vitamin D binds to a protein called the vitamin D receptor (VDR), which is present in almost every cell in the body. This receptor plays a role in various physiological processes, making vitamin D essential for proper bodily functions. The hormone impacts calcium, magnesium, and phosphate absorption in the intestines, among other biological effects.

Different Forms and Bioefficacy:

A big issue of ambiguity arises when discussing the specific compounds used for vitamin D supplementation. Terms such as cholecalciferol, ergocalciferol, calcidiol, and calcitriol are often used interchangeably, causing confusion. Cholecalciferol (d3) occurs naturally in nature. In comparison, ergocalciferol (d2) is a synthetic and less stable alternative. Recent evidence suggests that ergocalciferol is less potent and more susceptible to breakdown. As we will show below, neither should be supplemented. Calcitriol is the active form of vitamin D, which is believed to bring the alleged benefits. We will look at this further, and raise some interesting concerns. Ultimately, we need a healthy diet and sufficient sunlight to produce more calcitriol (Active-D). Interestingly, Active-D has a short half-life, but boron can significantly increase its duration.

Unveiling the Financial Interests Behind Vitamin D Supplementation

When understanding certain aspects of the healthcare industry, following the money often provides valuable insights. In the case of vitamin D supplementation, it is worth examining the financial interests that back its promotion. Big pharmaceutical companies have heavily supported the widespread use of vitamin D supplements, as evidenced by the significant market size projections. However, a closer look at the development of lab test ranges and the involvement of influential figures raises questions about the validity and potential risks associated with vitamin D supplementation.

The Influence of Financial Interests:

The global vitamin D market has experienced substantial growth, with a value of USD 1.23 billion in 2021 and an expected increase to USD 2.40 billion by 2030, as reported by Spherical Insights & Consulting. These figures indicate the substantial financial backing and vested interest in promoting vitamin D supplementation.

Lab Test Ranges and Misleading Information:

The rise of vitamin D supplementation can be attributed, in part, to influential figures like Michael F. Holick, whose recommendations have shaped medical practices and testing standards. Lab test ranges for vitamin D were developed by biased researches such as Michael F. Holick, PhD, MD, from Boston University, and John J. Cannell, MD, associated with the Vitamin D Council. These individuals are known proponents of vitamin D supplementation and have documented financial interests in promoting it. However, concerns have been raised about the accuracy and validity of these test ranges, which focus on an incorrect form of the vitamin D metabolite, potentially leading to misleading information.

The Potential Risks of Over-Supplementation:

Many scientists and researchers believe that the excessive supplementation of vitamin D has played a significant role, if not a major factor, in the modern health epidemic. The pattern of detrimental health effects associated with substances backed by big pharmaceutical and food companies is increasingly evident. This raises concerns about widespread vitamin D supplementation’s potential risks and unintended consequences. We will explore this further below.

How Is Vitamin D Made and Activated?

Vitamin D is activated through a complex series of enzymatic reactions, and it plays a pivotal role in our overall health. From maintaining calcium homeostasis and promoting bone health to regulating immune function, vitamin D exhibits a wide range of physiological effects. Understanding the pathways of vitamin D activation and its operations in the body helps us appreciate the importance of sunlight exposure and a balanced diet for maintaining optimal vitamin D levels and overall well-being.

The Sunlight Connection:

When ultraviolet (UV) photons from sunlight touch our skin, they interact with cholesterol chemicals present in the skin. This interaction provides energy that excites these chemicals, leading to their breakdown and the production of vitamin D precursor, as well as an abundance of cholesterol sulfate.

Skin Synthesis of Vitamin D:

With a sufficient diet and healthy sun exposure, our bodies can create approximately 90% of their vitamin D needs, specifically cholecalciferol, in the lower layers of the skin’s epidermis. This process occurs through a photo-chemical reaction of UVB light from sunlight or UVB lamps. However, it’s important to note that this form of vitamin D, like the one obtained through diet or supplementation, is biologically inactive.

Activation of Vitamin D:

To activate the biologically inactive vitamin D, it undergoes two protein enzyme hydroxylation steps. The first step occurs in the liver, converting cholecalciferol to calcifediol (25-hydroxycholecalciferol). The second step takes place in the kidneys, where calcifediol is further hydroxylated to form calcitriol (1,25-dihydroxycholecalciferol), the active form of vitamin D. Calcitriol acts as a hormone, producing effects via a nuclear receptor found in multiple locations throughout the body.

Functions of Calcitriol:

Calcitriol, the biologically active form of vitamin D, circulates as a hormone in the blood and is crucial in regulating calcium and phosphate concentrations. It promotes healthy growth and remodeling of bones, and it influences cell growth, neuromuscular and immune functions, and inflammation reduction. Calcitriol also has other effects, including some on cell growth, neuromuscular and immune functions, and reduction of inflammation.

Transportation and Activation in the Body:

After being converted into calcifediol in the liver, vitamin D is carried via the blood to the kidneys, where it is further hydroxylated to form calcitriol. This active form is released into the circulation and transported throughout the body, including the intestine, kidneys, and bones. Calcitriol binds to vitamin D-binding protein, facilitating its distribution and enabling it to mediate the physiological actions of vitamin D.

Vitamin D and Calcium Homeostasis:

One of the primary roles of vitamin D is maintaining calcium and phosphorous levels in the body. It achieves this by promoting calcium absorption in the intestines, increasing osteoclast number to stimulate bone resorption, and facilitating proper functioning of parathyroid hormone. Vitamin D and boron are critical for bone remodeling and preventing conditions such as osteoporosis.

Vitamin D, Cells, and the Immune System:

Vitamin D also exerts effects on the immune system. Its receptor, VDR, is expressed in various white blood cells, including monocytes and activated T and B cells. Vitamin D influences cell proliferation, differentiation, and the expression of genes related to immune responses. It plays a vital role in modulating body defenses against microbial invaders by stimulating the innate immune system.

Could Retinol, Vitamin A, be the Missing Piece of the Vitamin D Puzzle?

The activation of vitamin A, also known as retinol, by sunlight is not only important for our metabolism but also triggers the biosynthesis of vitamin D. A study conducted in 2008 explored the dynamic relationship between vitamin A and vitamin D metabolism, shedding light on their interconnected roles.

According to the study “Role of Fat-Soluble Vitamins A and D in the Pathogenesis of Influenza: A New Perspective,” the presence of retinol (vitamin A) in our diet is crucial for activating the VDRs. The actions of active vitamin D rely on these VDRs, which in turn depend on the presence of RXR (Retinoid X Receptors), a type of nuclear receptor that requires retinol to be available in the diet. It is through the complexing of vitamin D with RXR that the necessary gene transcription actions take place, ultimately impacting the immune system.

The historical lack of vitamin A in the typical American diet, dating back to 1955, could be a contributing factor to the prevalence of genetic defects seen today. The combined ability of VDR and RXR, as they form a protein complex called a heterodimer, plays a significant role in the immune system’s functionality. RXR is a crucial nuclear regulatory ligand in our metabolism, which may be lacking in individuals adhering to low-fat diets. The active metabolites of vitamin D are present in immune system cells such as monocytes, dendritic cells, memory T cells, and B cells, all of which are vital components of our body’s immune defense.

Recognizing the interplay between retinol (vitamin A) and vitamin D sheds light on their symbiotic relationship. The availability of retinol is crucial for activating vitamin D receptors, which, in turn, require the presence of RXR. By appreciating the significance of both VDR and RXR in our immune system and understanding their nutritional requirements, we can gain a more comprehensive understanding of optimal health.

Cholesterol Sulfate: Unveiling Its Importance

According to Dr. Seneff and Morley Robbins, cholesterol sulfate is a molecule of paramount significance. Contrary to popular belief, many of the purported advantages attributed to vitamin D are attributable to cholesterol sulfate. The protection against cancer, diabetes, cardiovascular disease, and the enhancement of immune function, which conventional medicine attributes to Storage D, can be largely credited to this sulfated form of cholesterol rather than the supplemental form of vitamin D.

It is crucial to recognize that all the benefits commonly associated with vitamin D are primarily derived from its active metabolite rather than the storage form that is conventionally measured. Unfortunately, there is a lack of responsible measurement when assessing the levels of Active-D.

According to Dr. Kenny De Meirleir, a highly regarded endocrinologist based in the Netherlands, the value of Active-D should ideally range from 1.5 to 2.0 times the level of storage vitamin D. Any excess beyond this range indicates an infection and suggests that active hormone D is being converted into Acute Microbial Peptides (AMPs) to combat pathogens that thrive on excessive, unbound iron.

The Controversy Surrounding Vitamin D Supplementation: Separating Fact from Fiction

Questioning the Benefits:

Despite the widespread belief in the benefits of vitamin D supplementation, scientific studies paint a more uncertain picture. Vitamin D supplementation has only been shown to be a reliable method for preventing or treating rickets. Research has failed to establish a consistent link between vitamin D supplementation and reduced rates of non-skeletal diseases such as cardiovascular disease, cancer, and diabetes. Furthermore, studies have not shown significant effects on bone fractures or osteoarthritis. These findings challenge the notion that vitamin D supplementation is a panacea for overall health improvement.

The effects of vitamin D supplementation on non-skeletal health are uncertain. A review found no effect from supplementation on the rates of non-skeletal disease other than a tentative decrease in mortality in the elderly. Vitamin D supplements do not alter the outcomes for myocardial infarction, stroke or cerebrovascular disease, cancer, bone fractures, or knee osteoarthritis.

Vitamin D2 vs. Vitamin D3:

Regarding vitamin D supplementation, not all forms are created equal. As previously mentioned, there is a lot of confusion around the forms and types of vitamin D. The most commonly supplemented forms are ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). While researchers and professionals often consider these forms equivalent, recent studies challenge this assumption. Evidence suggests that vitamin D3 is more effective at raising serum 25-hydroxyvitamin D levels, has better binding to vitamin D binding protein, and has a more natural metabolism and longer shelf life. Consequently, vitamin D2, or ergocalciferol, should not be considered suitable for supplementation or fortification. And I would argue that all forms should not be supplemented.

The Role of Magnesium and Mineral Imbalances:

One crucial factor to consider in vitamin D metabolism is magnesium. Magnesium is essential for the synthesis, transport, and regulation of vitamin D in the body. Studies have demonstrated that low magnesium levels hinder the metabolism of vitamin D and can lead to imbalances in mineral levels. Supplemental vitamin D can deplete magnesium stores and disrupt mineral dynamics, resulting in metabolic crises and potential health issues. As we all know, most people are already deficient in magnesium. Further, it’s been known since 1962, according to the research of John Ferris, MD, at Yale Medical School, that supplemental vitamin D causes renal (kidney) potassium wasting. 

Vitamin D Supplementation: Unraveling the Inflammatory Connection

In the realm of vitamin D research, Meg Mngin, RN, and co-founder of Chronic Illness Recovery, has made significant contributions by exploring the link between inflammation and vitamin D. A seminal research paper published in the journal Inflammation Research in 2014 sheds light on the intricate relationship between low blood levels of storage D (25-hydroxyvitamin D or 25(OH)D) and inflammation, challenging the necessity of routine vitamin D testing.

Importantly, Mngin highlights that the current method of determining vitamin D status may be flawed. The level of 25(OH)D, the form commonly tested, does not always reflect the level of 1,25-dihydroxyvitamin D (Active-D). It is crucial to distinguish the actions of storage-D and active-D as they are neither interchangeable nor synonymous.

An intriguing finding from Mngin’s research is that although vitamin D is often recommended to prevent and reverse chronic inflammation, studies do not support this notion. In fact, evidence suggests the opposite. Low levels of storage D indicate inflammation in the body, primarily caused by imbalances in iron and magnesium levels. Evidence implies that consuming large amounts of supplemental vitamin D may not address the underlying inflammation resulting from mineral dynamics, such as excess iron accumulation and magnesium deficiency within the cells.

Adding to the complexity, Mngin points out that low calcidiol levels, often labeled as vitamin D deficiency, and high calcitriol levels are markers of a chronic inflammatory process in sick individuals. Low calcidiol is not the cause but a consequence of a disease process. Supplementing with vitamin D can increase calcidiol levels, making it easier for the body to produce excess calcitriol, intensifying inflammatory symptoms.

It is worth noting that numerous studies have observed that individuals, despite being healthy and living in sunny regions, have levels of calcidiol deemed deficient according to current standards. This suggests that low calcidiol levels may be normal for healthy individuals. Moreover, studies examining disease occurrence have not demonstrated any beneficial effects of increasing calcidiol levels through vitamin D supplementation.

Mngin’s research highlights that low-storage vitamin D is merely a sign of the consequence of high inflammation rather than its cause. Additionally, individuals who are considered healthy tend to have low levels of Storage D but maintain normal levels of Active-D. Conversely, individuals who are chronically ill exhibit low storage D levels alongside elevated levels of active-D. Their bodies utilize the extrarenal bioactive vitamin D, produced outside the kidney tissue, as an antimicrobial peptide (AMP) to combat pathogens thriving on excess iron in the body. The disruption of vitamin A metabolism and impaired iron recycling caused by Storage D contribute to this inflammatory response.

As pointed out in our book and other posts, it is important to recognize inflammation itself is not a disease but rather a clear indication of metabolic imbalance resulting from mineral dysregulation or excess toxins. 

This imbalance is initiated and perpetuated by vitamin D supplementation, underscoring the need for a comprehensive understanding of the complex interplay between inflammation, mineral dynamics, toxins, and vitamin D.

By unraveling the intricate relationship between vitamin D supplementation and inflammation, mineral dynamics, and toxins, we gain valuable insights into the potential consequences of the indiscriminate supplementation of vitamin D. As a result of this insight, we should approach vitamin D supplementation cautiously or, ideally, avoid supplementation when not absolution necessary.

The Significance of Sulfation and the Limitations of Supplemental Vitamin D

Stephanie Seneff, PhD, highlights an important aspect of vitamin D metabolism—its sulfation. For vitamin D to effectively reach cells throughout the body, it must undergo sulfation. Unlike the natural, sun-derived sulfated form of vitamin D, fat-soluble vitamin D obtained through supplementation lacks the ability to circulate as efficiently. Instead, when we consume vitamin D supplements, our bodies store it.

The problem arises when we consume excessively high doses of synthetic supplemental vitamin D. This disrupts the body’s natural mechanism to regulate cholesterol levels properly. It also hampers the production of sulfated vitamin D, which is the water-soluble form that the body requires for optimal functioning. Research by De Luca (1997) and Seneff (2010) sheds light on this topic, emphasizing the significance of sulfated vitamin D. 

Moreover, supplemental vitamin D interferes with the absorption of retinol, a form of vitamin A. As the dosage of vitamin D increases, the availability of retinol diminishes, leading to a range of health issues. 

Ironically, these are the same problems supplemental vitamin D claims to prevent and resolve. Mawon et al. (2013) discuss the role of fat-soluble vitamins A and D in the pathogenesis of influenza, highlighting the adverse consequences of disrupting the balance between these essential vitamins. 

Challenging Popular Beliefs: The Complexities of Hormone D and Bone Health

Contrary to a widely held opinion surrounding the hormone D myth, there is no direct association between the active form of vitamin D [1,25(OH)2D3] and the hormone D metabolite crucial for building bone matrix, known as 24r, 25-dihydroxyvitamin D. This critical metabolite, essential for maintaining bone integrity, is more closely linked to the status of parathyroid hormone rather than Active-D. It’s important to note that parathyroid hormone, like all calcium-regulating hormones, relies on adequate magnesium levels for optimal function. 

Furthermore, a series of studies conducted by researchers at the University of Auckland in Australia have yielded conclusive evidence that hormone D supplements fail to improve bone integrity and contribute to tissue calcification. These studies provide significant insight into the detrimental metabolic and mineral effects associated with hormone D supplementation.

Additional studies shed light on the adverse metabolic and mineral impacts of hormone D supplementation, further highlighting its potential harm:

Renal Potassium Wasting: Ferris et al., 1962, “Renal Potassium-Wasting Induced by Vitamin D” 

Loss of Renal Energy Production and Increased Iron Storage: Zager et al., 1999, “Calcitriol Directly Sensitized Renal Tubular Cells to ATP-Depletion- and Iron Mediated Attack” 

The Complexities of Vitamin D: Conflicting Findings and Controversial Recommendations

According to a report by the US Institute of Medicine (IOM), there is a lack of reliable and consistent evidence linking calcium or vitamin D intake to various health outcomes, including cancer, cardiovascular disease, hypertension, diabetes, metabolic syndrome, falls, physical performance, immune functioning, autoimmune disorders, infections, neuropsychological functioning, and preeclampsia. These findings have sparked debates among researchers, with some arguing that the IOM’s recommendations were overly definitive and may have involved a mathematical error in calculating the blood level of vitamin D associated with bone health. However, members of the IOM panel defend their approach, stating that they followed standard procedures for dietary recommendations and that the report is firmly grounded in the available data. The complexity surrounding the effects of vitamin D on different health conditions underscores the need for further research and a cautious interpretation of existing evidence.

Exploring the Impact of Vitamin D on Mortality

The effects of vitamin D supplementation on overall mortality have been subject to investigation, particularly in the elderly population. Tentative findings suggest that vitamin D3 supplementation may reduce the risk of death in older individuals. However, the extent of this effect has yet to be deemed significant or certain enough to make widespread supplement recommendations. On the other hand, other forms of vitamin D, such as D2, alfacalcidol, and calcitriol, do not have any beneficial effects in terms of mortality risk.

It is worth noting that maintaining optimal blood levels of vitamin D appears to be associated with a lower risk of death. However, it remains to be seen whether supplementation can truly provide this benefit. Interestingly, both excess and vitamin D deficiency have been linked to abnormal functioning and premature aging, indicating the delicate balance required for optimal health.

The relationship between serum calcifediol concentrations, a marker of vitamin D status, and all-cause mortality follows a “U-shaped” pattern. Mortality rates tend to be elevated at high and low calcifediol levels compared to moderate levels. Furthermore, it is important to acknowledge that the potential harm from vitamin D appears to occur at a lower vitamin D level in the black population than in the white population, highlighting potential racial disparities in the effects of vitamin D on mortality.

Given the complex nature of these findings, further research is necessary to understand the impact of vitamin D on mortality fully and to guide appropriate supplementation practices.

Exploring the Role of Vitamin D in Bone Health

The effectiveness of vitamin D supplements in preventing osteoporosis, a common belief, lacks substantial evidence. Generally, using vitamin D supplements for osteoporosis prevention may not be necessary for individuals without vitamin D deficiency. We also need to explore the impact of sufficient levels of boron. However, for older individuals with osteoporosis, combining vitamin D with calcium may help prevent hip fractures, albeit with a slight increase in the risk of stomach and kidney problems. A study revealed that supplementation with 800 IU or more daily in individuals over 65 was somewhat favorable in preventing hip and non-vertebral fractures. The effect, however, is minimal or non-existent for those living independently. Low serum vitamin D levels have been associated with falls and low bone mineral density. Nevertheless, taking additional vitamin D does not appear to alter the risk.

Athletes deficient in vitamin D face an elevated risk of stress fractures and major breaks, particularly those involved in contact sports. Similar risks extend to deficiencies in boron and copper. The greatest benefit from vitamin D supplementation is observed in deficient athletes (25(OH)D serum levels <30 ng/mL) or severely deficient (25(OH)D serum levels <25 ng/mL). As serum 25(OH)D concentrations rise, incremental decreases in risks are observed, with the benefits plateauing at 50 ng/mL and no additional advantages observed beyond this point.

A 2020 systematic review by Cochrane found limited evidence suggesting combining vitamin D with calcium, but not when taken independently, may improve healing in children with nutritional rickets. However, the evidence was inconclusive regarding the reduction of fractures.

In summary, while the evidence supporting the use of vitamin D supplements for osteoporosis prevention is lacking, there may be some benefits for older individuals with osteoporosis when combined with calcium. Athletes deficient in vitamin D are at an increased risk of fractures, and supplementation can benefit those with deficiency levels. 

Exploring the Link Between Vitamin D and Cancer

Low vitamin D levels have been potentially linked to an increased risk of developing various types of cancer. Meta-analyses of observational studies have indicated a reduced incidence of cancer associated with higher vitamin D intake and 25(OH)D levels, especially in the case of colorectal cancer. However, the strength of these associations is considered weak. And may, in fact, be a correlation between metabolic dysfunction and inflammation rather than a cause. While randomized controlled trials have not confirmed that vitamin D supplements decrease the risk of cancer incidence, several meta-analyses have shown a lower relative risk of cancer deaths by up to 16%.

There is some evidence suggesting a potential association between low vitamin D levels and cancer risk, particularly colorectal cancer. However, the strength of these associations is not robust. Although randomized controlled trials have not shown a significant reduction in cancer incidence with vitamin D supplementation, meta-analyses suggest a lower relative risk of cancer-related deaths. Further research is needed to fully understand the relationship between vitamin D and cancer and its implications for prevention and treatment.

Exploring the Relationship Between Vitamin D and Cardiovascular Disease

Studies have shown that vitamin D supplementation is not linked to a reduced risk of stroke, cerebrovascular disease, myocardial infarction, or ischemic heart disease. Additionally, supplementation does not significantly impact lowering blood pressure in the general population.

Research conducted thus far indicates that vitamin D supplementation alone does not provide substantial cardiovascular benefits or offer protection against these specific cardiovascular conditions. It is important to note that other factors, such as a healthy lifestyle, balanced diet, regular exercise, and appropriate medical management, play crucial roles in maintaining cardiovascular health.

While Active-D is essential for overall health and well-being, vitamin D’s supplementation and influence on preventing cardiovascular disease are limited. Therefore, individuals should focus on comprehensive cardiovascular risk reduction strategies encompassing various lifestyle factors and medical interventions rather than relying solely on vitamin D supplementation.

Exploring the Role of Vitamin D in Infectious Diseases

Vitamin D plays a crucial role in activating the innate immune system and modulating the adaptive immune system, which provides it with antibacterial, antiviral, and anti-inflammatory properties. Low vitamin D levels have been identified as a potential risk factor for tuberculosis, and historically, it has been used as a treatment for the disease.

Regarding respiratory tract infections, vitamin D supplementation in low doses (400 to 1000 IU/day) may slightly reduce the overall risk of acute infections. This benefit has been observed primarily in young children and adolescents aged 1 to 16 years and has not been consistently confirmed with higher doses (>1000 IU per day or more).

In individuals with baseline 25(OH)D levels below 25nmol/L, vitamin D supplementation has significantly decreased the rate of moderate or severe exacerbations of chronic obstructive pulmonary disease (COPD). However, this effect is not observed in individuals with less severe deficiency.

Overall, vitamin D supplementation shows promise in supporting immune function and reducing the risk of certain infectious diseases. However, the optimal dosage and specific populations that can benefit the most from supplementation require further research and clarification. 

Exploring the Relationship Between Vitamin D and Inflammatory Bowel Disease

Two prevalent forms of inflammatory bowel disease (IBD), namely Crohn’s disease and ulcerative colitis, have been linked to low levels of vitamin D. Extensive research and a meta-analysis focusing on individuals with IBD and vitamin D deficiency have demonstrated the effectiveness of vitamin D supplementation in normalizing vitamin D levels. Moreover, supplementation has shown promising associations with improvements in clinical disease activity scores and biochemical markers. However, this is a case where correlation does not mean causation. And as mentioned above, vitamin D supplementation can also cause IBD and other gut dysfunctions.   

Examining the Impact of Vitamin D on Diabetes

Research suggests that vitamin D supplementation has notable effects on diabetes, particularly type 2 diabetes and prediabetes. A comprehensive meta-analysis revealed that vitamin D supplementation significantly reduced the risk of type 2 diabetes in non-obese individuals with prediabetes. Another meta-analysis indicated that supplementation led to improvements in glycemic control, including homeostatic model assessment-insulin resistance (HOMA-IR), hemoglobin A1C (HbA1C), and fasting blood glucose (FBG) levels in individuals with type 2 diabetes.

Furthermore, prospective studies have shown that higher levels of vitamin D are associated with a significant decrease in the risk of type 2 diabetes, combined type 2 diabetes and prediabetes, and prediabetes alone. 

Additionally, a Cochrane systematic review from 2011 examined a study that demonstrated how vitamin D, when used alongside insulin, helped maintain fasting C-peptide levels better than insulin alone over a 12-month period. It’s important to note that the available studies included in this review had notable flaws in quality and design, highlighting the need for further research.

Exploring the Effects of Vitamin D on Mental Health


Clinical trials investigating the impact of vitamin D supplementation on depressive symptoms have generally exhibited low quality and have not shown an overall effect. However, subgroup analysis revealed a moderate effect when supplementation was targeted at participants with clinically significant depressive symptoms or depressive disorder.

Cognition and Dementia:

A systematic review of clinical studies identified a correlation between low vitamin D levels and cognitive impairment and a higher risk of developing Alzheimer’s disease. However, it’s important to consider that lower vitamin D concentrations can also be associated with poor nutrition and reduced outdoor exposure. Therefore, alternative explanations exist, and a direct causal relationship between vitamin D levels and cognition could not be firmly established.


Trials have consistently indicated that individuals with schizophrenia, particularly during acute episodes, tend to have lower vitamin D levels compared to the general population.

While vitamin D shows potential associations with mental health conditions such as depression, cognition, and schizophrenia, further research is needed to understand the underlying mechanisms and establish clearer causal relationships fully.

Exploring the Impact of Vitamin D on Pregnancy

Low vitamin D levels during pregnancy have been associated with several adverse outcomes, including gestational diabetes, preeclampsia, and small-for-gestational-age infants. While taking vitamin D supplements during pregnancy can increase maternal blood levels of vitamin D at term, the exact extent of benefits for both the mother and baby remains unclear. And the risks, as mentioned earlier, are high. However, adequate vitamin D intake during gestation is linked to a lower risk of preeclampsia and positive immune effects. Additionally, vitamin D supplementation is likely to reduce the risk of gestational diabetes and the likelihood of having undersized babies with poor growth rates. It is worth noting that pregnant women often do not meet the recommended intake of vitamin D. Nor do they have sufficient nutrition and sun exposure.

Further research is needed to fully understand the comprehensive effects of vitamin D supplementation during pregnancy and its potential long-term benefits and risks for both the mother and baby.

Exploring the Relationship Between Vitamin D and Weight Loss

While there has been speculation that vitamin D supplementation could aid in weight loss independent of calorie restriction, a systematic review found no significant association between supplementation and changes in body weight or fat mass. However, a meta-analysis conducted in 2016 revealed that weight loss was associated with improved circulating vitamin D levels, suggesting a potential inverse relationship between fat mass and vitamin D status in the bloodstream.

These findings indicate that weight loss efforts may positively impact vitamin D levels. Still, the evidence does not support the notion that vitamin D supplementation alone leads to significant weight reduction. It is important to consider comprehensive approaches to weight management, including mineral optimization, ancestral diet, and regular physical activity, while ensuring adequate sunlight exposure. 

Vitamin D Toxicity and Its Complex Interactions

Instances of vitamin D toxicity are rare and primarily occur due to excessive supplementation rather than sun exposure. The specific threshold for vitamin D toxicity has not been established definitively. Still, research suggests that a daily intake exceeding 4,000 IU (100 μg) for individuals aged 9-71 may exceed the tolerable upper intake level (UL). 

Additionally, sustained intake of over 50,000 IU (1250 μg) per day in healthy adults can lead to overt toxicity, resulting in elevated serum 25-hydroxyvitamin D levels above 150 ng/mL. Certain medical conditions, like primary hyperparathyroidism, can increase sensitivity to vitamin D, causing hypercalcemia. Pregnant women with elevated calcium levels may expose their fetuses to developmental issues and intellectual disabilities.

Published cases of toxicity indicate that intake exceeding 40,000 IU (1,000 μg) per day can lead to hypercalcemia. However, it is important to note that adverse effects are generally observed at serum concentrations of 25(OH)D above 200 nmol/L.

Pregnant or breastfeeding individuals should consult with a doctor before considering vitamin D supplementation due to potential risks.

While the focus is often on vitamin D toxicity, it is crucial to understand the broader implications and disruptions caused by excessive storage of vitamin D. Calcitriol, the active form of “vitamin D,” stimulates the production of nitric oxide, which opens the FPN pathway. Insufficient copper levels can result in unregulated iron release, leading to detrimental effects on cellular health and potentially triggering conditions such as leaky gut syndrome.

Moreover, the optimal expression of active vitamin D relies on its interaction with the nuclear receptor RXR, which requires real vitamin A (retinol). Unfortunately, the emphasis on vitamin D often overshadows the significance of vitamin A. Additionally, the impact of vitamin D supplementation on intestinal vitamin A absorption remains largely unknown.

It is essential to recognize that nothing in nature operates in isolation. All elements are interconnected, and vitamins A and D share a powerful relationship. Sunlight’s role in activating the breakdown of vitamin A into essential retinoids is ten times more critical than synthesizing vitamin D. Despite historical research on retinol in the 1920s, today’s focus predominantly centers on vitamin D storage. This disregard for past discoveries and the pioneering work of researchers like Hopkins and Eijkman, who received the Nobel Prize in 1929 for their vitamin research, is unfortunate.

At the end of the day, the risks of supplementing vitamin D far outweigh their benefits in all cases aside from Rickets. Instead, focus on optiming your minerals, eating an ancestral diets, and getting sufficient movement and sunlight.  


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