How does the menstrual cycle affect blood sugar levels?
Hormonal fluctuations of estrogen and progesterone during the menstrual cycle have an impact on glucose metabolism and insulin sensitivity.
The menstrual cycle is separated into the follicular phase (pre-ovulation) and the luteal phase (post-ovulation). The follicular phase is characterized by low progesterone and a short rise and fall of estrogen, and the luteal phase demonstrates rising estrogen and progesterone, with a drop in both before menstruation due to lack of fertilized egg.
Hormonal fluctuations during the menstrual cycle. Source
During the menstrual cycle, the body engages in energetically intense processes like ovulation and building up the uterine lining to receive a fertilized egg. Sex hormones like estrogen and progesterone appear to play a role in energy metabolism, insulin sensitivity, and how glucose is processed in the body. In general, estrogens seem to promote insulin sensitivity, and progesterone promotes insulin resistance.
"In general, estrogens seem to promote insulin sensitivity, and progesterone promotes insulin resistance."
Research has shown that glucose concentrations in the luteal phase (post-ovulation) are significantly higher than in the follicular phase. Concordantly, in some studies, there is an increase in insulin resistance in healthy women during the luteal phase of the menstrual cycle (when the progesterone-to-estrogen ratio is high) in comparison to the follicular (pre-ovulation) phase (when the estrogen-to-progesterone ratio is high). This suggests that the reduction in insulin sensitivity during the luteal phase depends on the increased level of progesterone.
Estradiol (estrogen) improves the expression of insulin signaling molecules in skeletal muscle. Estrogens exert beneficial metabolic effects by lowering body-fat and improving insulin sensitivity in females. Insulin sensitivity is higher in the follicular phase and decreased in the luteal phase.
In some studies, fasting insulin rises before ovulation. It reaches a maximum during the luteal phase, indicating relative insulin resistance during the luteal phase of the cycle in agreement with studies showing lower insulin sensitivity in the luteal phase using glucose tolerance tests.
Based on this literature, given relative insulin resistance during the luteal phase (post-ovulation), it seems reasonable to focus on minimizing glucose (and insulin) stimulating foods during this time to minimize the glycemic impact of this phase.
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