What are the dietary requirements for each phase of the menstrual cycle?

Dietary Requirements by Menstrual Cycle Phase

While micro- and macronutrient requirements change across menstrual cycle phases due to hormonal fluctuations, the foundation must be adequate total energy availability of 45 kcal·kg⁻¹ fat-free mass·day⁻¹—optimizing nutrient composition by cycle phase is futile without meeting basic energy needs first. 1

Foundational Principle: Energy Availability First

Before adjusting nutrients by cycle phase, ensure adequate total caloric intake 1:

• Target: 45 kcal·kg⁻¹ fat-free mass·day⁻¹ for optimal health and menstrual function 1, 2
• Inadequate energy availability disrupts menstrual patterns regardless of nutrient composition 2
• This baseline must be met before phase-specific adjustments matter 1

Phase-Specific Dietary Adjustments

Follicular Phase (Days 1-14)

Characterized by rising estrogen and low progesterone 3

Protein Requirements:

• Minimum 1.6 g·kg⁻¹·day⁻¹ during this phase 1
• Distribute evenly throughout the day and after exercise 1
• This should be the primary macronutrient focus when planning daily intake 1

Carbohydrate Strategy:

• Early follicular phase is optimal for muscle glycogen storage when combined with high carbohydrate intake 3
• Gluconeogenesis rates are higher during follicular phase at exercise intensities >50% VO₂max 1
• Carbohydrate intake reaches its lowest point during the periovulatory period, approximately 2 days after ovulation 4

Energy Intake Pattern:

• Total energy intake tends to be lower during follicular phase compared to luteal phase 4, 5
• Weight typically decreases during the periovulatory phase 6

Ovulatory Phase (Around Days 12-14)

Marked by sharp LH surge, peak estrogen and FSH 3

Metabolic Considerations:

• Minimum caloric intake occurs around ovulation (approximately 2 days after) 4
• Fat and total energy intake reach their lowest point during this period 4
• Despite metabolic changes, this phase does not significantly impair exercise performance at low altitudes 3

Luteal Phase (Days 15-28)

High estrogen and progesterone levels 3

Protein Requirements:

• Increase protein intake above 1.6 g·kg⁻¹·day⁻¹ due to higher progesterone-induced protein catabolism 1, 3
• ACSM recommends 1.2-2 g·kg⁻¹·day⁻¹, with the higher end appropriate for luteal phase 1

Carbohydrate Strategy:

• Consume high carbohydrate snack 3-4 hours before exercise to mitigate impaired gluconeogenesis during luteal phase 1
• Women are less reliant on muscle glycogen during luteal phase due to high estrogen levels 1
• Estrogen enhances lipid oxidation and reduces carbohydrate metabolism during exercise 1, 3

Energy and Macronutrient Increases:

• Significant increases occur during luteal phase: 5, 6
  • Total energy: +159 kcal (0.66 MJ) compared to follicular phase 5
  • Protein: +6.1 g 5
  • Carbohydrate: +15.3 g 5
  • Fat: +8.6 g 5
• Caloric intake increases significantly during both periovulatory and luteal phases compared to follicular phase 6

Micronutrient Needs:

• Higher intakes during luteal phase: vitamin D, riboflavin, potassium, phosphorus, and magnesium 5
• Iron, vitamin D, and calcium deficiencies are particularly common and require attention throughout the cycle 1

Practical Weekly Algorithm

Week 1 (Menstruation/Early Follicular):

• Baseline protein: 1.6 g·kg⁻¹·day⁻¹ 1
• Emphasize high carbohydrate intake for glycogen storage 3
• Focus on iron-rich foods due to menstrual blood loss 1

Week 2 (Late Follicular/Ovulation):

• Maintain protein at 1.6 g·kg⁻¹·day⁻¹ 1
• Expect natural decrease in appetite around ovulation 4
• Continue carbohydrate emphasis as gluconeogenesis is still elevated 1

Weeks 3-4 (Luteal Phase):

• Increase protein toward 2 g·kg⁻¹·day⁻¹ to offset catabolism 1, 3
• Add 150-200 kcal daily to meet increased energy needs 5
• Consume pre-exercise carbohydrate snack 3-4 hours before activity 1
• Increase micronutrient-dense foods (vitamin D, riboflavin, potassium, phosphorus, magnesium) 5

Critical Caveats

Avoid These Pitfalls:

• Never restrict total calories below energy availability threshold (45 kcal·kg⁻¹ FFM·day⁻¹) while attempting phase-specific optimization 1, 2
• Severely restricting carbohydrates while increasing protein can disrupt menstrual patterns 2
• Vegetarian diets during caloric restriction carry higher risk of anovulation—7 of 9 women became anovulatory on vegetarian diet versus maintaining ovulation on nonvegetarian diet during weight loss 7
• Dieting (800-1000 kcal/day) can disrupt menstrual cycles even in normal-weight women, causing anovulation and decreased estradiol to menopausal levels 8

Monitoring Indicators:

• Menstrual cycle irregularities signal inadequate energy availability 2
• Cycle length changes or amenorrhea require immediate dietary assessment 1, 8
• Vegan/vegetarian athletes need particular attention to meet protein requirements without specialized guidance 1