Ah, caffeine—the magical elixir that fuels our mornings, powers our workouts, and helps us survive the mid-afternoon slump. But have you ever wondered what it’s actually doing to your hormones? If you’re dealing with irregular cycles, mood swings, or stubborn weight gain, your daily cup (or three) of coffee might be playing a bigger role than you think.

We’re not here to tell you to quit your beloved brew, but understanding how caffeine affects your body can help you make more informed choices. So, let’s dive into the science behind caffeine and hormones—especially oestrogen, cortisol, insulin, and thyroid function.

Caffeine and Cortisol: A Stressful Relationship

Cortisol, often called the “stress hormone,” plays a key role in regulating metabolism, immune function, and blood sugar levels. Caffeine can cause a surge in cortisol, mimicking the body’s natural stress response. This isn’t necessarily bad—short-term, it can boost alertness and energy. However, if you’re already dealing with high stress, frequent caffeine consumption may keep your body in a constant state of “fight or flight,” leading to:

• Increased anxiety and jitters
• Sleep disturbances
• Blood sugar imbalances
• Adrenal fatigue (especially in women with already taxed adrenal glands)

If you’re drinking coffee on an empty stomach first thing in the morning, you’re spiking cortisol without any food to help buffer the response. Consider pairing your coffee with a protein-rich breakfast to minimize the stress effect.

Oestrogen, PMS, and Fertility: Does Caffeine Play a Role?

Research suggests that caffeine metabolism varies based on genetics and even ethnicity, but one thing is clear: caffeine influences oestrogen levels, particularly in women. A study published in the American Journal of Clinical Nutrition found that caffeine increases oestrogen levels in some women while decreasing it in others.

For those struggling with oestrogen dominance—symptoms like heavy periods, bloating, and breast tenderness—caffeine may exacerbate the issue. Additionally, high caffeine intake has been linked to delayed conception and an increased risk of miscarriage, making it something to monitor if you’re trying to conceive.

When it comes to fertility, research shows that more than 200mg (about 2 cups of coffee) per day can increase the risk of miscarriage and can delay the time to pregnancy. 3 cups of coffee per day (by both men and women) may increase the risk of miscarriage by 74%.  Some studies suggest that caffeine could delay ovulation or increase the time it takes to fall pregnant. This may be due to the fact that caffeine can deplete the body of crucial vitamins and minerals needed for hormone balance (like b vitamins and magnesium). And it affects male fertility too. Excessive caffeine intake can cause DNA damage to sperm which can lead to chromosomal abnormalities and an increased risk of miscarriage.

Caffeine and Blood Sugar: The Hidden Impact on Insulin

Caffeine affects insulin sensitivity, meaning it can make it harder for your body to regulate blood sugar. If you’re prone to sugar crashes, cravings, or even PCOS, caffeine may be making things worse by:

• Increasing blood sugar spikes and crashes
• Contributing to insulin resistance over time
• Leading to increased hunger and sugar cravings

Pairing coffee with healthy fats (like a splash of coconut milk) and protein can help blunt these effects.

Thyroid Function: Could Coffee Be Slowing You Down?

If you have hypothyroidism or Hashimoto’s, caffeine may interfere with thyroid hormone absorption—especially if you drink it close to taking your medication. It can also contribute to nutrient depletion (iron and magnesium, for example), which are essential for thyroid function. If you’re dealing with sluggish metabolism, fatigue, or thinning hair, caffeine might not be helping.

So, How Much is Too Much?

The answer depends on your unique body, genetics, and hormone balance. But here are some general guidelines:

• If you have adrenal fatigue, hormone imbalances, or fertility concerns, consider limiting caffeine to 100-150 mg per day (about one small cup of coffee) or switching to lower-caffeine options like matcha.
• If you’re generally healthy, up to 300-400 mg per day (about 2-3 cups of coffee) is considered safe, but timing matters—avoid caffeine late in the day to protect sleep and cortisol rhythms.
• Listen to your body! If caffeine makes you anxious, disrupts your cycle, or worsens PMS, consider cutting back.

Smarter Swaps and Practical Tips

If you’re not ready to quit caffeine but want to support hormone balance, try these:

• Swap coffee for matcha—it has caffeine but also L-theanine, which promotes calm focus. Koyu, Clearsprings, Solaris are a few of my fav brands)
• Try herbal adaptogens like maca or ashwagandha to support stress resilience. (London Nootropics have a love range)
• Opt for decaf or half-caf options if you’re sensitive.
• Make sure to drink coffee with food, not on an empty stomach, to reduce cortisol spikes.

Final Thoughts

Caffeine isn’t the enemy, but understanding its impact on your hormones can help you make better choices for your body. If you feel amazing with your daily cup of coffee, great! But if you’re struggling with hormonal imbalances, anxiety, or sleep issues, experimenting with your caffeine intake might be the missing piece of the puzzle.

What’s your relationship with caffeine? Have you noticed any changes when you cut back?

I’d love to hear from you,

Noeleenxx