You need to eat a lot to build muscle, but overdo it and you'll just build a gut. Luckily, getting enough of this vitamin shifts calories towards muscle growth, not fat storage.
The dream of every lifter? To have the ability to eat large amounts of food and convert those calories into muscle, not store them as fat. We already know we can shift calories toward building muscle and away from fat storage with nutrient-partitioning agents like C3G. Now, a new study shows that vitamin D also has this ability.
The study
First, this early-stage study used mice, but the researchers think the same mechanisms of action may apply to humans. The title of the study is certainly intriguing: "High-dose dietary vitamin D allocates surplus calories to muscle and growth instead of fat via modulation of myostatin and leptin signaling."
Some background: Our conventional understanding is that surplus calories are stored as fat. We know that leptin from fat regulates appetite and energy expenditure, but in obesity, leptin resistance blunts this effect. We also know that myostatin from muscle limits muscle growth, while its absence increases muscle mass. The interplay between leptin and myostatin in energy allocation is poorly understood, and vitamin D's influence on calorie allocation is unclear.
With all that in mind, the researchers gave mice high doses of vitamin D. In a nutshell, here's what they found:
- Vitamin D shifts calorie usage. High-dose vitamin D redirected surplus calories toward muscle growth, rather than fat storage.
- Decreased myostatin reduced inhibition of muscle growth. Increased leptin sensitivity boosted energy expenditure without increasing appetite. Together, these effects improve "energy balance sensing," not just energy storage.
- High vitamin D increased grip strength, lean mass, and energy expenditure. Fat mass decreased, but appetite and physical activity were unchanged. High-dose vitamin D effectively improved body composition at constant weight.
A new paradigm
In short, the old model proposed that leptin alone signals fat stores; surplus calories default to fat storage. The proposed new model (energy balance sensing) says that vitamin D integrates leptin and myostatin signaling. Anticipated energy needs (via myostatin) and nutrient status (via vitamin D) influence where calories are allocated: muscle growth, fat storage, etc.
This study shows for the first time that high-dose vitamin D reprograms energy/calorie allocation, a new paradigm.
How to use this info
Extrapolating this info to humans is difficult. For example, the mice were given different amounts of vitamin D per kilogram of diet, not per kilogram of body weight.
However, if we strip it all down, the take-home point for humans is to shoot for high-normal levels of serum vitamin D. That's classically defined as above 30 ng/mL. But many progressive researchers think we should go much higher, up to around 70 ng/mL.
Basically, don't become deficient in vitamin D if you want to optimize how your body uses calories. A rough extrapolation of the data, combined with a proven method of correcting vitamin D deficiency, would look something like this:
- Take 50,000 IU of vitamin D over five days. That's 10,000 IU daily.
- Take around 5000 IU daily to keep vitamin D levels in the high-normal range.
Ideally, use microencapsulated vitamin D3. This is the most bioavailable and longest-lasting form. This is especially important if you're middle-aged or older. Here's why.
Biotest D Fix (Buy at Amazon) contains 5000 IU of microencapsulated vitamin D per softgel.
Reference
- Roizen, Jeffrey, et al. "High Dose Dietary Vitamin D Allocates Surplus Calories to Muscle and Growth Instead of Fat via Modulation of Myostatin and Leptin Signaling." Research Square, 2024, doi:10.21203/rs.3.rs-4313931/v1. PubMed, PMID: 38766160; PMCID: PMC11100886.