Hello Runner,
Welcome back to your weekly moment of endurance nutrition!
Happy Weekend!
How are you?
I'm fine, but I've had a tough week.
I can’t quite explain why, but this past week I was extremely irritable. At least I realized I wasn’t feeling well, so I took some time for myself. I needed to listen to myself and find some peace.
I kept up with my workouts, but I took it easier with my running and focused on mobility exercises and yoga instead. That really helped.
We all go through rough patches and tough times; what matters is recognizing when we’re not doing well and taking care of ourselves.
Even though it was tough, I worked REALLY HARD this week, and I have some news that you’ll hear about soon.
Today, I’ll be talking about the nutritional recommendations for women engaged in endurance sports during their menstrual period. I will explain whether these recommendations change throughout the phases of the menstrual cycle.
The menstrual cycle is not just a reproductive event; it is a monthly hormonal fluctuation that directly affects how a woman’s body burns carbs and fat, how much protein she needs, how thirsty she is, how warm her run is, and how quickly she bounces back after a hard session.
→ Understanding this means you can stop guessing and start responding to what your body is already signalling.
The cycle is most helpfully broken down into two main phases: the follicular phase (day one of bleeding through to ovulation, roughly days 1-14) and the luteal phase (post-ovulation through to the day before your next period, roughly days 15-28). Within those two broad phases, you have four distinct hormonal environments, each with its own metabolic fingerprint.
And each one asks for slightly different nutritional awareness, especially when you are running or training hard.
The research in this area is growing, but it is also still catching up. For many years, female athletes were simply excluded from sports science studies altogether, or tested once with no regard for cycle phase. But recent work from bodies including the IOC and ACSM is changing this.
The thing is that women don’t need to follow a rigid phase-based protocol, but understanding the mechanisms gives them better tools to interpret their own experience and make smarter day-to-day choices.
Importantly, symptoms (e.g., cramps, fatigue, GI distress) often matter more than the hormonal phase alone in guiding nutrition decisions.
Let's see what happens in each cycle and what to prioritize.
Phase 1: Your Period (Early Follicular Phase)
This is when hormones are lowest, and metabolism is actually more “stable.”
What runners often feel:
- Fatigue, cramps, low motivation
- Slower recovery
- Sometimes reduced appetite
How to fuel:
Prioritize iron (non-negotiable)
You lose iron through menstrual bleeding, and endurance running increases your risk further
Low iron = reduced oxygen delivery = slower runs
Runner tip:
Add iron-rich foods this week:
Lean red meat, eggs, lentils, spinach
Pair with vitamin C (e.g., citrus) for better absorption
Read my last email about Iron to get all the recommendations.
Keep carbs consistent
Your body uses carbohydrates more efficiently in this phase
Stick with your normal fueling (especially before and after runs)
The ISSN recommends 5-7g of carbs per kilogram of body weight daily for moderate-to-hard endurance training
Reduce inflammation & symptoms
Omega-3s (salmon, mackerel, sardines, chia seeds, flaxseeds)
Turmeric + black pepper
Stay hydrated, even if you don’t feel like it
Follicular Phase (Post-Menstruation → Ovulation)
Hormones (especially estrogen) rise, and many runners feel their best here (peak performance).
What runners often feel:
- Enhanced mood
- Motivation
- Coordination and better neuromuscular function
What’s happening:
Better insulin sensitivity
Higher carbohydrate use
Stronger high-intensity performance potential
How to fuel:
Lean into carbs!
Your body is primed to use glycogen efficiently
Great time for:
Speed workouts
Long runs with quality segments
Keep protein steady
~1.4–2.0 g/kg/day supports recovery and adaptation
Ovulation: Peak Performance Window
This is often when you feel strongest, fastest, and most powerful.
→ No special diet needed. But remember to fuel well, hydrate normally, and take advantage of the momentum!
Phase 2: Luteal Phase (Post-Ovulation → Pre-Menstruation)
After ovulation, progesterone and estrogen rise. And this is where nutrition matters most.
What runners often notice:
- Higher effort at the same pace
- Increased body temperature
- More cravings
- Appetite increases
- Slight drop in endurance (~small but noticeable)
Runner tip:
Eat a little more: Add ~100–300 kcal/day
Especially from carbs + protein
Ignoring this = higher risk of fatigue and underperformance.
Time your carbs strategically
Your body shifts toward using more fat and less carbohydrate.
→That sounds good, but for performance, it might not be.
Fix it:
Prioritize carbs before and during runs
Training lasting longer than 90 min or at high intensity, target 40-50g of carbs per hour
Slightly increase protein
There’s evidence of increased protein breakdown in this phase.
Aim for:
~1.6–2.0 g/kg/day
Think about 20-25g of high-quality protein post-run recovery
Hydrate smarter
Progesterone increases:
Core temperature
Sweat rate
Sodium loss
Runner tip:
Monitor hydration more closely
Don’t rely on thirst alone
Add electrolytes (especially sodium) around longer (>90 minutes) training sessions.
Manage cravings
Cravings are biologically driven.
Instead of restriction, choose complex carbs: whole grains (oats, quinoa, brown rice), legumes (lentils, black beans, chickpeas), starchy vegetables (sweet potatoes, potatoes, corn), and fiber-rich fruits.
Support energy metabolism
At this phase, magnesium requirements may increase to support muscle and nerve function, bone density, metabolism, and sleep quality.
Good sources include whole grains, legumes, nuts, seeds, dark chocolate, and dark leafy greens.
The Most Important Thing Most Runners Miss
Across all phases:
→ Low Energy Availability (LEA) is the real performance killer
Studies consistently show that many female endurance runners:
Undereat (especially carbs and total calories)
Have low iron intake
Risk of menstrual dysfunction and RED-S
About Relative Energy Deficiency in Sport (REDs)→ the IOC's updated 2023 consensus statement is clear: energy availability below 45 kcal per kilogram of fat-free mass per day disrupts hormonal function, impairs performance, compromises bone health, and derails long-term runners’ health.
This impacts performance far more than the cycle phase itself.
The menstrual cycle isn’t a limitation.
We, female runners, cannot ignore it, but we need to understand our bodies and adapt to it.
Track your cycle, note how you feel, and experiment with intentional nutritional shifts that can make a real difference to how you train, recover, and race.
Over time, patterns emerge, and that’s where performance gains live.
Product of the Week
This week's Product of the Week is the Kuik's Coconut and Pineapple Hydrating Drink.
This drink caught my eye because I’d never seen a low-carb drink sweetened with stevia and monk fruit, which are natural sweeteners.
I thought it was an interesting option because it’s light, tasty, and has a very summery (with summer just around the corner) coconut-pineapple flavor. Plus, it contains some electrolytes that help with hydration.
Kuik is a Spanish sports supplement brand made especially by women, and they make some really interesting products.
The only catch is that since it’s still a small brand, they only ship to Spain and the Balearic Islands. But it’s worth trying.
Track of the Week 🎧️
This week's Track of the Week is a song with a great beat to listen to while running. This song screams summer, another one for the hot-weather playlist.
I’ve chosen I Adore You Feat. Daecolm by HUGEL, Topic, Arash, Daecolm
Any questions or something you would like to share, drop me an email
Wishing you a great weekend and week ahead!
Here’s to health and good runs⚡️
Ana Paula Alonso