Mary Daniels shares her experience navigating the changes of training and nutrition during pregnancy. Every pregnancy is different, and what matters most is adaptability.
We talk a lot about fueling, recovery, and supplements for endurance athletes. Today we wanted to share something a little different.
Mary Daniels (formerly Denholm) is a pro runner, ultrarunner, and coach. She's also 39, based in Boulder, and just weeks away from welcoming her first daughter. We sat down with her to talk about what training and nutrition through pregnancy actually look like for a high-level endurance athlete.
The first thing she said? Every pregnancy is different. She's coached about 20 women through it, and no two experiences look the same. So take everything here as one athlete's story, not a prescription.
Training through pregnancy
Mary entered pregnancy running 100 to 120 miles a week. By the first trimester, she was at 60 to 70. Still running six to seven days a week, still doing interval work, but no tempo, no doubles, nothing sustained at threshold.
"Tempo never felt good pregnant, so I just did not do it."
Her doctors confirmed it: sustained threshold (or higher) efforts are what to avoid. Short hard intervals are fine, as long as recovery follows. What mattered most was adaptability.
By the second trimester, she switched to uphill intervals only. Less jostling, better recovery, easier on the joints as her center of gravity shifted. She also started wearing a pregnancy support belt around 18 to 20 weeks; her advice is to get one earlier than you think you need it.
Third trimester, she moved to running by time instead of distance. What used to be an eight-mile run became five. She stayed on trails, avoided technical terrain, and kept everything easy.
She finished pregnancy at over 2,000 miles and over 250,000 feet of vert.
Fueling — more than you'd expect
One of the biggest surprises was how much she needed to eat.
During long runs in her first and second trimester, Mary was taking in 120 to 150g of carbs per hour, well above her usual 100. She rotated through different gels constantly to avoid palate fatigue, and never finished a pregnant long run feeling empty.
"I honestly just think it's because my body is so busy growing this life too."
Day to day, she ate every two hours. First trimester had its brown food days — salt and vinegar chips, bagels, one very specific crispy chicken sandwich craving she couldn't explain. Her advice: get in the calories and eat often to cut down on nausea. Do your best. If your body wants something, listen to it.
Supplements She Trusted
Mary kept her routine pretty simple:
Thorne Prenatal — her daily foundation to support her pregnancy.
Thorne Advanced Iron Complex — she entered pregnancy with high ferritin and credits it for her energy levels throughout. Her advice: don't wait until you're pregnant to address iron. The baby takes everything, and if your ferritin is already low going in, it can be more challenging to increase your iron levels.
Momentous Plant-Based Chocolate Protein — a shake after every run. She trusts their third-party testing, and getting 20g of protein helped her recover effectively.
Dream Shot — she loves it, but paused it during pregnancy because of the ashwagandha. It's on her list to come back to postpartum.
What's Next
Her baby is due in June. Mary isn't signed up for anything, and she's okay with that. She's targeting CCC in August 2027 as her goal race, and hopes to race again around six months postpartum, but she's leaving room for eight if that's what her body needs.
"You have to treat it like coming back from an injury. Be patient, don't force a timeline."
We are wishing Mary a safe delivery and are excited to see her run into motherhood.
