Running While Breastfeeding: The Art of Balancing Energy Management and Milk Production

Introduction

Many Taiwanese mother runners face a practical dilemma after choosing to breastfeed: “Will running affect my milk supply? Will my baby still drink my milk after exercise? Do I even have the energy to run right now?” Running while breastfeeding does require additional management strategies, but as long as you understand the physiological mechanisms and prepare properly, you can absolutely do both well.

Energy Demands During Breastfeeding

Breastfeeding is one of the periods of highest energy demand in a woman’s life:

• Baseline lactation cost: Producing 100 mL of breast milk requires approximately 67 kcal
• Average daily milk production: 750–1000 mL, equivalent to an additional 500–700 kcal/day
• Plus running expenditure: At approximately 60 kcal per km, running 40 km per week adds roughly 2400 kcal/week

Important warning: If breastfeeding runners do not correspondingly increase their dietary intake, they can easily fall into the RED-S (Relative Energy Deficiency in Sport) trap, leading to decreased milk supply, increased fatigue, delayed return of menstruation, and other issues.

Changes in Breast Milk After Exercise: A Scientific Clarification

"It’s common to hear that ‘milk tastes sour after a run, so the baby won’t drink it,’ but research offers a more nuanced conclusion:

Practical recommendations:

• If doing low-to-moderate intensity running, nursing before or after exercise is fine
• If doing high-intensity intervals, rest briefly after finishing before nursing, or express milk from before the run to feed the baby

Practical Challenges of Running While Breastfeeding

1. Breast Fullness and Discomfort

• Accumulated milk makes the breasts heavy, causing uncomfortable bouncing while running
• Solution: Schedule runs after nursing or pumping, when the breasts are lighter; choose high-support sports bras (see Part 11 of this series for details)

2. Joint Stability

• Relaxin continues to be secreted during breastfeeding, and ligament laxity may persist for several months after weaning
• Pay special attention to ankle stability and surface selection

3. Fatigue Accumulation from Sleep Deprivation

• Fragmented sleep from newborn care has a major impact on training recovery
• HRV (heart rate variability) drops significantly with insufficient sleep
• Recommendation: Use HRV or subjective fatigue (Borg RPE) as the daily guide for training intensity; “whether to run today” matters more than “how much to run”

4. Dehydration Risk

Lactation itself requires an additional 500–700 mL of fluid per day, and combined with sweat loss from running, the risk of dehydration rises substantially. Dehydration not only affects exercise performance but may also affect milk supply.

• Fluid target: Breastfeeding runners are advised to drink 3–3.5 L per day
• Drink 300–500 mL 30 minutes before running
• Replenish 150–200 mL every 20 minutes
• After running, replace sweat losses (every 1 kg of body weight lost ≈ requires 1000 mL)

Dietary Strategies for Breastfeeding Runners

Key Areas to Increase in Your Diet

• Do not diet: Breastfeeding is not the time for weight loss; your body needs adequate energy to maintain milk production
• High-quality protein: 1.6–2.0 g per kg of body weight per day, to support muscle repair and lactation
• Complex carbohydrates: Sweet potatoes, brown rice, oats, to stabilize blood sugar and prolactin levels
• Omega-3 fatty acids: Fish oil or deep-sea fish, beneficial for infant brain development; supplementation by nursing mothers can be passed through breast milk
• Calcium and vitamin D: Calcium needs are high during breastfeeding, and it is prioritized for milk production; if intake is insufficient, it will be drawn from the mother’s bones

Practical Tips

• Change “nurse after running” to “run after nursing”: Run when the breasts are emptiest and most comfortable
• Don’t push to return to pre-pregnancy weight by 6 months postpartum: Moderate body fat stores during breastfeeding are a normal protective mechanism
• Communicate with family about running time: The fatigue of caring for a newborn combined with run training requires partner and family support
• Shorter, more frequent runs are more suitable than longer, less frequent ones: Easy runs of 3–5 km, 4–5 times per week, are easier to schedule and recover from than one long run per week

Conclusion

Running while breastfeeding is absolutely feasible, but you need to put “your body’s needs” ahead of “training goals.” When you are simultaneously nourishing a new life and maintaining your own running habit, you are already doing something truly remarkable. Give yourself a little more patience and give your body a little more fuel—you can do both very well.

Related Reading

• Nutrition for Pregnant and Postpartum Athletes: A Complete Fueling Map from Pregnancy, Postpartum Recovery to Breastfeeding
• Dietary Analysis for Road Running: Methods to Track Food Intake and Identify Energy Gaps
• Fluid Loss and Running Performance: Quantifying the Impact of Losing 1% of Body Weight
• Dietary Planning for Marathon Training: Dynamic Adjustments Between Training Load and Calorie Intake