Vitamin D is a powerful nutrient that impacts nearly every system in the body.
This includes:
1. Bones and Teeth
2.
The Immune System
3. Mood and Mental Health
4. Heart Health
5. Hormone Regulation
6. Inflammation
7. Sleep
8. Brain Function and Cognitive Health
and more
New research suggests that the “sunshine vitamin” plays a crucial role in determining whether your body stores calories as fat or builds muscle instead.
Today we investigate the research to learn exactly how this powerful nutrient influences hormones like leptin and myostatin, two powerful regulators of body composition—and how optimizing your Vitamin D intake could completely change the way your body stores and burns energy.
Obesity occurs when the body stores excess calories as fat instead of muscle. Fat produces the hormone leptin, which regulates energy balance by signaling the brain. Changes in fat mass are reflected by corresponding changes in leptin levels. High levels typically signal the brain to reduce appetite and increase energy expenditure. However, in obesity, the brain becomes less sensitive to leptin, weakening these effects.
Our understanding of the factors that regulate leptin production in fat or leptin sensitivity in the brain is still limited.
Similarly,
muscles produce myostatin, a hormone that functions in muscle tissue in a similar manner as leptin in fat. The absence of myostatin leads to increased muscle mass and strength. Like leptin, the mechanisms controlling myostatin production and sensitivity are not well understood. While fat and muscle mass are closely interconnected, the relationship between leptin and myostatin remains unclear.
Vitamin D Signaling and Nutrient Sensing
Vitamin D signaling, mediated by the activation of the vitamin D receptor, plays a crucial role in conveying nutrient status to the brain. The vitamin D receptor is the primary mediator of this signaling pathway(1).
VDR Knockout Mice and Failure-to-Thrive Phenotype
Mice lacking the vitamin D receptor exhibit a “failure-to-thrive” phenotype, characterized by: Abnormal serum calcium and phosphate levels, poor growth and
significantly reduced white fat. This phenotype is partly attributed to decreased storage of lipids into white fat, which is the primary producer of leptin(2).
Leptin and Vitamin D Signaling
White fat produces the majority of circulating leptin, a hormone that plays a key role in regulating appetite and energy balance. The lack of white fat in vitamin D receptor knockout mice results in persistently low leptin levels(3).
Vitamin D Signaling and Muscle Function
Low vitamin D levels are known to cause muscle weakness. Studies have traditionally examined Vitamin D effects through induced deficiency, using dietary restrictions or vitamin D receptor knockout. Recent clinical studies suggest that increasing vitamin D within the normal range may have beneficial effects on muscle function(4).
Interconnectedness of Fat and Muscle Mass
Fat mass and muscle mass are closely linked, although the precise mechanisms are poorly understood. Interventions that increase muscle mass often led to increased fat mass, and vice-versa. Significant weight loss (over 10% of baseline) results in proportional losses of both muscle and fat.
Myostatin and Energy Needs
Myostatin is thought to have a homeostatic effect on muscle mass. Emerging data suggests that myostatin may also play a role in conveying energy needs. Conventional vitamin D receptor knockout mice have low serum leptin, and muscle-specific vitamin D receptor knockout mice show excess myostatin mRNA production(2).
Research Objective
Recent research aimed to explore the relationship between vitamin D signaling, fat mass, muscle mass, and muscle function. The study investigated the effect of both normal-to-low and normal-to-high dietary vitamin D levels(5). The diets allowed the investigators to achieve target serum 25(OH)D of less than 5 ng/mL, between 20–30 ng/mL and above 30 ng/mL.
Key Findings and Themes
Vitamin D and Myostatin/Leptin
Replenishing Vitamin D levels to normal reduces myostatin production. Further increasing Vitamin D does not cause further reductions in serum myostatin. This is significant because myostatin inhibits muscle growth.
Vitamin D replenishment increases the amount of leptin produced per unit of fat mass. Higher doses of Vitamin D increase sensitivity to leptin. Leptin, while not directly impacting appetite, plays a key role in the body’s energy expenditure.
Calorie Allocation
High-dose Vitamin D promotes the allocation of excess calories to building muscle (fat-free mass) instead of being stored as fat. This is achieved by increasing leptin production and sensitivity and decreasing myostatin signaling.
Energy Balance Sensing
The study proposes a new model for understanding energy balance. Rather than energy stores alone determining calorie use (e.g., simple storage as fat), the model emphasizes the importance of “anticipated energy needs,” as conveyed by myostatin, in determining calorie allocation. Calorie intake will be allocated also to linear growth, fertility or to build muscle in addition to energy expenditure and fat storage(5).
This shifts the paradigm from one of “energy stores sensing” to “energy balance sensing.” See graphic below:
Figure: In the Conventional Model (left side) energy stores sensing is mediated by leptin and by default excess calories are stored as fat. b) in High dose Vitamin D (b, at bottom). This research indicates a role for vitamin D in modulating energy balance sensing as well as calorie allocation. i)Vitamin D increases (+) leptin production and sensitivity (overall increasing leptin signaling (bold arrow)), and ii.) vitamin D decreases myostatin production (decreasing myostatin signaling (thin arrow)), leading to iii)increased energy expenditure, linear growth and improved fertility as well as iv) increased allocation of excess calories to muscle (bold arrow) (Figure adapted from Roizen et al. 2024(5)
Therapeutic Implications
Common conditions such as obesity, sarcopenia (age-related muscle loss), and chronic inflammatory diseases often present with low Vitamin D levels. These findings suggest high-dose Vitamin D may have therapeutic potential in addressing such conditions, especially to help reallocate calories towards muscle gain rather than fat storage(5).
The work suggests that manipulating leptin sensitivity, potentially via Vitamin D, might be an avenue to combat obesity, something that has not been successful with exogenous leptin alone.
Seasonal Variation
Vitamin D acts as a long-term nutrient availability signal (seasonal), affecting how the body utilizes calories, i.e. promoting fat storage during times of low Vitamin D (winter) and muscle and linear growth when Vitamin D is high (late summer/early fall).
The work potentially explains the long-observed seasonal variation in human growth patterns (more growth in the summer/fall) and may also explain why vitamin D improves fertility and helps modulate seasonal fertility patterns.
Strengths and limitations of the Research
Strengths of this research were the multidimensional assessment of muscle function, metabolism, and fat mass and the examination of the effects of low, normal, and high-normal vitamin D in healthy mice. A limitation is still not full understanding the precise mechanistic steps through which Vitamin D decreases myostatin and increases leptin signaling are not fully elucidated.
So, where can you get Vitamin D?
The recommended daily value (DV) for vitamin D is 600 IU (15 mcg) for adults up to age 70 and 800 IU (20 mcg) for those over 70, but many experts suggest higher doses for optimal health.
Vitamin D deficiency is common, especially in people with limited sun exposure, darker skin tones, or those living in northern climates, so it’s important to make sure you are getting enough from your food or supplementation.
Sources include:
- Sunlight exposure
- Fatty fish (salmon, mackerel, sardines, tuna)
- Cod liver oil
- Egg yolks
- Beef liver
- Cheese (especially Swiss and cheddar)
- Mushrooms (shiitake, maitake, UV-exposed mushrooms)
- Fortified milk (cow, almond, soy, oat)
- Fortified orange juice
- Fortified cereals
- Fortified yogurt
- Fortified tofu
- Supplements
Final thoughts on the importance of vitamin D
This research highlights how Vitamin D plays a crucial role in managing the body’s energy use and nutrient distribution. Instead of just storing energy, it helps the body sense and adjust to both available energy and future needs.
These findings could lead to new treatments for different health conditions and help explain seasonal changes in growth and fertility. However, more studies are needed to fully understand how this works and confirm the results in humans.
If you’re looking for a simple way to ensure you get enough Vitamin D every single day, look no further than
ONE+.
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References:
1. Christakos S, Dhawan P, Verstuyf A, et al: Vitamin D: Metabolism, Molecular Mechanism of Action, and Pleiotropic Effects. Physiol Rev 96:365-408, 2016
2. Narvaez CJ, Matthews D, Broun E, et al: Lean phenotype and resistance to diet-induced obesity in vitamin D receptor knockout mice correlates with induction of uncoupling protein-1 in white adipose tissue. Endocrinology 150:651-61, 2009
3. Matthews DG, D’Angelo J, Drelich J, et al: Adipose-specific Vdr deletion alters body fat and enhances mammary epithelial density. J Steroid Biochem Mol Biol 164:299-308, 2016
4. Hassan-Smith ZK, Jenkinson C, Smith DJ, et al: 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 exert distinct effects on human skeletal muscle function and gene expression. PLoS One 12:e0170665, 2017
5. Roizen J, Long C, Casella A, et al: High dose dietary vitamin D allocates surplus calories to muscle and growth instead of fat via modulation of myostatin and leptin signaling. Res Sq, 2024
