Muscles need a combination of macronutrients for energy and growth, minerals that drive contraction and relaxation, and vitamins that support everything from nerve signaling to recovery. Protein gets most of the attention, but your muscles are equally dependent on carbohydrates for fuel, specific electrolytes to contract and relax, and a range of micronutrients that keep the whole system running. Here’s what each nutrient does and how much you actually need.
Protein: The Building Material
Protein provides the amino acids your body uses to repair and build muscle fibers. Of the 20 amino acids, leucine is the one that most directly triggers muscle protein synthesis, the process by which your body lays down new muscle tissue. Research estimates that you need about 3 to 4 grams of leucine per meal to maximally stimulate this process, which translates to roughly 25 to 30 grams of protein per meal.
For overall daily intake, a large meta-analysis found that eating around 1.6 grams of protein per kilogram of body weight per day maximizes muscle growth when combined with resistance training. Benefits taper off beyond that point, though intakes up to 2.2 grams per kilogram still show some additional effect. For a 70-kilogram (154-pound) person, that works out to about 112 to 154 grams of protein spread across the day. If you’re dieting and trying to hold onto muscle while losing fat, the target climbs higher, to roughly 2.3 to 3.1 grams per kilogram per day, because your body is more likely to break down muscle tissue when calories are restricted.
Spacing matters, too. Eating about 0.4 grams of protein per kilogram of body weight at each meal, spread across four meals, is a practical way to hit those daily targets while keeping muscle protein synthesis elevated throughout the day.
Carbohydrates: The Fuel Source
Carbohydrates are stored in muscle tissue as glycogen, which is the primary fuel for moderate-to-high-intensity exercise. When glycogen runs low, your muscles fatigue faster and performance drops. After a hard workout, current sports nutrition guidelines recommend consuming about 1.2 grams of carbohydrate per kilogram of body weight per hour for the first four to six hours to maximally replenish those stores.
An interesting shortcut exists if you’re also eating protein. When carbohydrate intake after exercise falls below about 0.8 grams per kilogram per hour, adding protein on top significantly boosts glycogen resynthesis. One practical approach is to eat 0.9 grams of carbohydrate and 0.3 grams of protein per kilogram per hour. This combination replenishes glycogen just as effectively as carbohydrate alone while simultaneously stimulating muscle repair. If you’re already eating enough carbohydrates post-workout, though, the added protein won’t speed up glycogen recovery further.
Healthy Fats and Omega-3s
Dietary fat supports muscle health in ways that go beyond just providing calories. Omega-3 fatty acids, specifically EPA and DHA found in fatty fish, are incorporated into muscle cell membranes, where they enhance the rate of muscle protein synthesis and reduce the expression of factors that drive muscle protein breakdown. They also serve as raw materials for compounds that resolve inflammation, which helps explain why omega-3 intake is linked to reduced muscle soreness after exercise.
These fats simultaneously inhibit pro-inflammatory gene activity and promote the production of specialized molecules called resolvins and protectins. The net effect is faster recovery and better preservation of muscle tissue, particularly during periods of inactivity or immobilization when muscles tend to waste quickly.
Calcium: The Contraction Trigger
Every single muscle contraction depends on calcium. When your brain sends a signal to move, calcium ions flood into the muscle cell and bind to a regulatory protein called troponin. This physically shifts another protein, tropomyosin, out of the way, exposing the binding sites that allow your muscle’s contractile filaments to slide past each other and generate force. Without calcium, those binding sites stay blocked and the muscle can’t contract at all. Calcium is not optional for muscle function; it is the switch that turns contraction on.
Magnesium: The Relaxation Partner
If calcium triggers contraction, magnesium helps muscles relax. Magnesium regulates the transport of calcium and potassium across cell membranes and controls neuron excitability, which determines how readily your nerves fire signals to your muscles. When magnesium levels drop, nerves become overexcitable and muscles can contract involuntarily.
Early signs of magnesium deficiency include muscle spasms, weakness, and fatigue. As deficiency worsens, symptoms progress to persistent cramps, numbness, and tingling. Severe depletion can cause tetany, a state of continuous, painful muscle contraction, along with dangerous heart rhythm abnormalities. Because magnesium homeostasis is tightly linked to sodium, potassium, and calcium balance, a shortage tends to disrupt your entire electrolyte system.
Iron: Oxygen Delivery to Muscle Cells
Iron sits at the center of two critical oxygen-carrying proteins: hemoglobin in your blood and myoglobin inside your muscle fibers. Hemoglobin shuttles oxygen from your lungs to your muscles; myoglobin stores it within the muscle cell and delivers it to the mitochondria, where it’s used to produce energy aerobically. Without adequate iron, both systems falter, and your muscles lose aerobic capacity.
Research on how the body prioritizes iron is revealing. When demand for red blood cell production spikes (as it does at high altitude), the body pulls iron away from muscle tissue. One study found that muscle myoglobin expression dropped by 35%, stored iron fell by 37%, and iron transport proteins decreased by 50% as the body redirected iron toward making more hemoglobin. This illustrates how tightly iron supply and muscle oxygen availability are connected, and why chronically low iron intake hits endurance performance hard.
Vitamin D and Muscle Size
Vitamin D deficiency is consistently associated with reduced muscle mass and weaker force production. Supplementing vitamin D in deficient individuals enhances muscle function and increases the cross-sectional area of individual muscle fibers, particularly in older adults and athletes. The mechanism appears to involve the vitamin D receptor, a protein expressed inside muscle cells. In lab studies, overexpressing this receptor caused muscle fibers to accumulate more protein and RNA, resulting in measurable hypertrophy. In humans, increases in vitamin D receptor gene expression after long-term resistance training correlated with gains in lean mass.
The practical takeaway: maintaining adequate vitamin D levels supports your muscles’ ability to grow in response to training. Deficiency undermines that process, and it’s remarkably common, especially in people who spend limited time outdoors or live at higher latitudes.
B Vitamins and Nerve-Muscle Communication
Your muscles can only function if the nerves controlling them are intact, and vitamin B12 plays a direct role in maintaining that connection. B12 promotes the survival of nerve cells and maintains myelin sheaths, the insulating layer around nerves that allows electrical signals to travel quickly and accurately to your muscle fibers. Without adequate B12, myelin degrades, nerve signals slow down, and muscles lose the precise input they need to contract effectively. Over time, this leads to peripheral neuropathy, characterized by weakness, numbness, and eventually permanent nerve degeneration.
Animal research has shown that B12 accelerates reinnervation of skeletal muscles after nerve damage and promotes regeneration of degenerating nerve terminals. For people getting enough B12 through diet, supplementation offers no extra benefit. But deficiency, which is more common in older adults and those eating little or no animal products, directly compromises the nerve pathways that control muscle movement.
Water: The Overlooked Performance Factor
Dehydration impairs muscle performance at every level. Losing just a small percentage of body water consistently reduces strength by about 2%, power output by about 3%, and high-intensity endurance by roughly 10%. These effects appear to stem from changes in the force-generating capacity of muscle fibers themselves, not just from feeling thirsty or overheated. Adequate fluid intake supports blood volume, nutrient delivery, waste removal, and the electrolyte balance that calcium and magnesium depend on to regulate contraction.
For most people, drinking enough water throughout the day and increasing intake around exercise is sufficient. The exact amount varies with body size, climate, and activity level, but the performance data makes it clear that even mild dehydration carries a measurable cost.