Women's Sports Nutrition: Hormones, Cycles, and Supplements

Sports nutrition isn't one-size-fits-all—women's needs differ due to hormones. Female athletes experience unique physiological demands influenced by fluctuating ovarian hormones—primarily estrogen and progesterone—across the menstrual cycle. These fluctuations affect metabolism, substrate utilization, recovery, bone health, and nutrient requirements.

Low energy availability (LEA), common in endurance and aesthetic sports, can disrupt menstrual function, leading to Relative Energy Deficiency in Sport (RED-S) and increased injury risk. Evidence from the International Society of Sports Nutrition (ISSN) position stand and recent reviews emphasizes personalized nutrition: ensuring adequate energy, carbs, protein, and key micronutrients like iron, calcium, and magnesium while syncing intake to cycle phases where possible.

Hormonal Fluctuations and the Menstrual Cycle

The menstrual cycle averages 28 days, divided into follicular (days 1–14, estrogen rising) and luteal (days 15–28, progesterone dominant) phases, with ovulation around day 14. Estrogen promotes carb oxidation, glycogen storage, and vascular function, while progesterone increases basal metabolic rate (BMR) by 5–10% and shifts toward fat utilization.

In eumenorrheic (regularly menstruating) women, performance metrics like VO2 max show minimal cycle-phase differences in most studies, but endurance may dip slightly in the late luteal phase due to higher inflammation and fluid retention. Oral contraceptive (OC) users experience suppressed natural fluctuations, with synthetic hormones altering metabolism—active pill weeks mimic follicular phase benefits, while placebo weeks may increase fatigue.

LEA exacerbates issues: 94% of elite female trail runners in a 2025 study had low EA (<30 kcal/kg FFM/day), linked to amenorrhea and poor bone health. Amenorrheic athletes often consume more simple carbs and protein but inadequate calcium and iron, highlighting the need for balanced fueling.

Iron and Calcium Focus

Iron

Iron is critical for oxygen transport via hemoglobin; deficiencies reduce VO2 max by up to 15%. Female athletes lose iron through menstruation (average 1–2 mg/day), sweat, GI losses, and footstrike hemolysis. RDI is 18 mg/day, but athletes need 20–30 mg due to demands.

Hepcidin (iron regulator) rises post-ovulation with progesterone, limiting absorption; estrogen suppresses hepcidin in the follicular phase for better uptake. Studies show 15–35% of female athletes are iron-deficient vs. 3–11% in males. Screen every 6 months (more frequently if LEA/amenorrhea). Sources: heme iron (meat) absorbs better, but pair plant sources (spinach, lentils) with vitamin C for 2–3x improved absorption. Avoid calcium and tea near iron meals.

Calcium

Calcium supports bone density; estrogen aids absorption and retention. The IOC recommends 1,500 mg/day for athletes (vs. 1,000 mg general population), spread in doses under 500 mg. Amenorrheic women risk 4x higher stress fractures due to low estrogen. Dairy, alternatives, leafy greens, and fortified foods help; use supplements (citrate or carbonate) if dietary intake falls short.

Magnesium

Magnesium aids muscle relaxation, energy production, and cramp reduction; luteal phase declines increase deficiency risk (studies show a 4.6% drop mid-luteal). RDA is 310–320 mg; athletes should aim higher (400 mg) from nuts, seeds, and whole grains.

Cycle-Syncing Nutrition

While evidence is emerging, tailoring macros and micros to your cycle phase can offer an edge:

Follicular Phase (Estrogen-Dominant)

Higher carb tolerance and better glycogen storage. Focus on 6–10 g/kg carbs for endurance; emphasize iron-rich foods during this phase when absorption is optimal.

Luteal Phase (Progesterone-Dominant)

5–10% higher BMR means increased caloric needs. Increase protein to the upper range (1.4–2.2 g/kg) to counter catabolism. Boost complex carbs and magnesium for mood and cramp management.

The ISSN recommends 0.32–0.38 g/kg high-quality protein peri-workout, with amounts at the higher end during the luteal phase. For OC users: active pill weeks mimic follicular benefits; placebo weeks may need extra recovery focus. Use tracking apps (Clue, Flo) and adjust 10–20% carbs/protein based on phase and energy levels.

Top Supplements for Female Athletes

Iron

Ferrous bisglycinate (gentle on stomach), 18–65 mg if deficient; pair with vitamin C. Highly efficacious per ISSN.

Calcium

500–1,000 mg/day if dietary intake is low; take with vitamin D for enhanced absorption.

Magnesium

300–400 mg (glycinate or citrate form); reduces cramps, supports sleep and recovery.

Creatine

3–5 g/day; benefits muscle, bone health, and mood (especially post-menopausal). One of the most evidence-backed supplements for female athletes.

Vitamin D

2,000–4,000 IU if deficient; aids calcium uptake and immune function.

Evidence is strongest for iron and creatine in females. Avoid over-supplementing—test levels first with regular bloodwork.

Implementation and Monitoring

Prioritize energy balance (>30 kcal/kg FFM). Track intake with apps like MyFitnessPal. Get bloodwork for ferritin, hemoglobin, and vitamin D every 3–6 months. If amenorrheic, increase energy 300–500 kcal/day to restore menses.

Consult a sports dietitian for personalization—cycle-syncing combined with proper supplementation can boost performance 5–10% while safeguarding long-term health.