General Info

• Caffeine (1,3,7-trimethylxanthine) is found in coffee, tea, soft drink, energy drinks, and chocolate ^[1]
• Caffeine, like cocaine, LSD, cannabis and more are psychoactive drugs, which alter brain function, mood and behaviour of ‘users’ ^[2]
• Caffeine enhances and promotes the use of other addictive substances including alcohol and nicotine ^{[3, 4, 5]}
• On average, 1 cup of coffee contains ~100 mg of caffeine ^[6]
• 1 can of energy drink contains 80 mg of caffeine ^[7]
• 1 cup of tea contains 50 mg of caffeine ^[7]
• 1 can of soft drink (coca cola) contains 50 mg caffeine ^[7]
• 100g bar of milk chocolate contains 20 mg of caffeine ^[7]
• Shockingly, ∼60% of pregnant women consume caffeine ^[8]

How Caffeine Impacts Male Fertility

Caffeine consumption in males increases the levels of reproductive hormones – including testosterone and sex hormone binding globulin – which in high amounts damages sperm DNA, interferes with the process of sperm production, and reduces all parameters of sperm health including the size and shape of sperm, the number of sperm, and the ability of sperm to move properly to reach the egg. This will result in infertility ^[9]

How Caffeine Impacts Female Fertility

• Caffeine affects female reproductive hormones which inhibits ovulation, causes irregular menstrual cycles, and leads to infertility ^[10]
• Consuming 200 mg or more of caffeine per day (2-3 cups of coffee) reduces oestradiol concentrations. This may affect ovulation and the ability to get pregnant ^[11]
• Consuming just 2-50mg of caffeine per day (less than half a cup of coffee) increases the risk of not becoming pregnant and increases the risk of miscarriage ^[12]
• Women who consume no coffee are twice as likely to become pregnant compared to women who moderately consume coffee ^[13,14]
• Even if undergoing IVF, caffeine must be ceased. Caffeine decreases the number of eggs retrieved through IVF which lessens the chance of conceiving ^[15]

Adverse Pregnancy Outcomes

• Caffeine crosses the placenta into the fetus and has a prolonged metabolism of around a 15 hour half life. This means that if a mother has 200mg caffeine at 9am (equivalent to a double shot of coffee), she would still have 100mg in her system at midnight, and would not completely clear the caffeine until 3pm the next day ^[16].
  Since the half life of caffeine in newborn is ~100 hours, that is a whopping 8 days a newborn is technically affected by one single cup of coffee! ^[17]
• The baby’s liver is unable to metabolise this amount of caffeine and faces an increased risk of being born with a low birth weight – that is, weighing less than 2.5 kg ^[18]
• In fact, increments of 100 mg caffeine per day (1 cup coffee or 2 cups of tea) increases the risk of your baby having a low birth weight by 7% ^[18]
• Low birth weight increases the risk a prospective child developing disease later in life – including obesity, diabetes mellitus, and high blood pressure ^[19]
• Caffeine consumption during pregnancy increases the risk of a prospective child becoming obese by 87% ^[20]
• Caffeine disturbs the uterine lining which prevents the implantation of a fertilized egg, therefore resulting in miscarriage ^[21]
• Consuming 100 mg of caffeine per day (1 cup coffee) increases the risk of miscarriage by 14% ^[18]
• Consuming more than 200 mg of caffeine per day (2 cups coffee) increases the risk of miscarriage by 31% ^[22]
• Caffeine consumption increases the risk of stillbirth by 19% ^[18]
• Women who consume more than 4 cups of coffee per day increase the risk of stillbirth by almost 80% ^[23]
• Maternal caffeine consumption may predispose a child to cognitive difficulties, including lowered IQ ^[24]
• Caffeine consumption during pregnancy affects hormone levels in the developing brain (frontal cortex and hypothalamus), which can lead to behavioural problems ^[8]
• Caffeine exposure in utero can inhibit the prospective child’s chance of conceiving in their adult life. This occurs as caffeine consumption during pregnancy decreases testosterone levels in male offspring. This hormonal shift decreases the weight of male reproductive organs, and decreases sperm size and shape, number, and ability to swim. Ultimately, increasing a child risk of infertility as an adult, even before birth^[25]
• Maternal caffeine consumption can reduce the size and shape of male offspring sperm by 25%, the number of male offspring sperm by 25%, and the ability of male offspring sperm to move properly by 13% ^[26]

References:
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482951/
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3181622/
[3] https://www.ncbi.nlm.nih.gov/pubmed/25593148
[4] https://www.ncbi.nlm.nih.gov/pubmed/29707859
[5] https://www.ncbi.nlm.nih.gov/pubmed/16330600
[6] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5733907/
[7] http://www.foodstandards.gov.au/consumer/generalissues/Pages/Caffeine.aspx
[8] https://www.ncbi.nlm.nih.gov/pubmed/28555252
[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482951/
[10] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5632691/
[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3260075/
[12] https://www.ncbi.nlm.nih.gov/pubmed/12093834
[13] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5007064/
[14] https://www.sciencedirect.com/science/article/pii/S0140673688909336
[15] https://www.ncbi.nlm.nih.gov/pubmed/21119578/
[16] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4400202/
[17] http://www.academicjournals.org/journal/AJPP/article-full-text-pdf/67DE98728415
[18] https://www.ncbi.nlm.nih.gov/pubmed/25179792/
[19] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4507998/
[20] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4389720/
[21] https://www.ncbi.nlm.nih.gov/pubmed/29276412
[22] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4196566/
[23] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3717046/
[24]https://www.researchgate.net/publication/284279227_Maternal_Caffeine_Intake_During_Pregnancy_and_Child_Cognition_and_Behavior_at_4_and_7_Years_of_Age
[25] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548072/
[26] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4181836/