Coffee is one of the most popular and safest stimulants that we consume. But during pregnancy, and potentially even when planning a pregnancy, it is one ‘legal drug’ where advice for women becomes a little more prescriptive. Alcohol, soft cheeses, raw fish and even raw sprouts are all foods that are best to limit or avoid during pregnancy. So, should coffee be added to the list and if so, how much is a safe amount to drink? That is what I’ll explore in today’s podcast.
Coffee, brew, black gold or go juice. Whatever you call it, coffee is the world's second most popular beverage after tea. It has been estimated that over 2.2 billion cups of coffee are drunk every day.
So just what’s in your daily brew? Coffee contains several useful nutrients, including riboflavin, niacin, magnesium, potassium, and various antioxidants as well as a bunch of other natural plant chemicals. In fact, one estimate has found that the typical Western diet provides more antioxidants from coffee than it does from fruits and vegetables combined.
And then of course, there is the caffeine. Caffeine is the most consumed psychoactive substance in the world – and I’m taking both legal and illegal substances here. Soft drinks, tea and chocolate all contain caffeine, but coffee is the biggest source.
Caffeine is a stimulant. In your brain, it blocks the function of an inhibitory neurotransmitter called adenosine. By blocking adenosine, caffeine increases activity in your brain and releases other neurotransmitters like norepinephrine and dopamine. This reduces tiredness and makes you feel more alert. That all means that caffeine can lead to a short-term boost in brain function, improving mood, reaction time, vigilance and general cognitive function. But any regular coffee drinker knows this already.
There are a surprising number of health benefits now being linked to regular coffee drinking - from a lower risk of developing T2DM through to even helping people struggling with mobility issues from Parkinson’s disease. I won’t go into the full story here but check back into podcast episode number 4 for the full low down on the surprising health benefits of coffee.
But for this podcast, I want to narrow in on one specific question: could your daily ‘coffee addiction’ be harming your chances of conceiving or even harming a developing foetus?
I’ll start with the good news straight off the bat: if you are trying to conceive, then there is no need to go cold turkey for caffeine. But I do need to make a disclaimer that it is certainly wise and recommended to keep your coffee habit down to the equivalent of two cups of coffee per day. Let me explain why.
Cutting back on caffeine is common fertility advice for women who are struggling to conceive or going through IVF. So, are there good grounds for this advice? If you go digging into the scientific research, you’ll find mixed messages. Some studies do find a link between caffeine and a woman's ability to conceive, while others find that it has no impact. But the quality of the research studies are not that great.
A link between caffeine and fertility is plausible because caffeine is known to have effects on ovulation and hormone levels. Another interesting theory is that caffeine can affect how the muscles in the fallopian tubes work. These muscles contract in smooth, rhythmic waves to help the egg on its journey to the uterus. So, caffeine here could disrupt this movement and affect the journey of the egg to its destination.
So, the experts conclude that there just isn't enough evidence to make a definitive conclusion about caffeine and fertility. But it is worth paying heed to the possibility and to keep your coffee habit in check when you’re trying to conceive.
Caffeine and IVF
Advice about caffeine also applies to women undergoing IVF. One recent study from Denmark that looked at nearly 1,700 women undergoing IVF at a large clinic found that women who drank up to 5 cups of coffee had similar fertility success compared to women who drank no coffee. And I’ll link to this study in the show notes. Although previous work from this same group did find that drinking more than five cups of coffee a day was linked to less chance of conception and live birth. So here for women undergoing IVF as well, conservative advice about keeping your coffee drinking to a couple of cups per day seems sensible. https://pubmed.ncbi.nlm.nih.gov/31043232
What about after conception?
That’s the story about conception and caffeine, but once a woman becomes pregnant, the advice about caffeine becomes much stronger - and for good reason. A systematic review and meta-analysis from 2017 which I’ll link to in the show notes found a 37 percent higher risk of miscarriage in women who consumed more than 300 mg of caffeine a day. And the risk of miscarriage more-than doubled with caffeine intakes above 600 mg/day https://pubmed.ncbi.nlm.nih.gov/29276412
Other research has also found that in women having more than 300 mg of caffeine each day is linked to foetal growth restriction, which could result in low birth weight.
And the findings of a major review on the adverse effects of caffeine on healthy adults, pregnant women, adolescents children from 2017 which I’ll link to in the show notes finds that up 300 mg of caffeine a day for pregnant women is considered safe while for non-pregnant adults, the safe limit goes up to 400 mg per day. https://pubmed.ncbi.nlm.nih.gov/28438661
None of this research is new or surprising as a link between caffeine and the risk of miscarriage has been known for some time which is why FSANZ advises that for pregnant and breastfeeding women daily caffeine consumption should not exceed 200mg which errs on the side of caution. This advice mirrored by similar European and US regulatory bodies that advise that during pregnancy no more than 200 mg of caffeine, that’s about 2 cups of coffee, should be drunk per day.
Just why too much caffeine could be an issue during pregnancy is because a woman's ability to metabolise caffeine slows during pregnancy. What's more, caffeine readily passes from the placenta to the growing baby, which has not developed enough to inactivate it. So the drug can accumulate in the baby's body and brain so it could be having a real development effect.
These are current recommendations, and they could be subject to revision in the future as more research becomes available as there are some voices in the medical community who argue that because there is a dose-dependent relationship between caffeine and risk, it portends that even lower doses below 200 mg/day could have an effect during pregnancy. And while it may be hard to quantify this risk from observational studies, it may be better to take a more conservative approach to caffeine recommendations and lower the upper limit of 200 mg. If you want to read the latest commentary around this topic, I’ll link to an article from 2020 in the show notes https://www1.racgp.org.au/newsgp/clinical/experts-conflicted-on-controversial-caffeine-pregn
Where do you find caffeine?
Quite rightly we associate coffee with caffeine, but you do find caffeine in a range of drinks and foods. So, it is good to be aware of where it may lurk if you’re keeping an eye on a 200 mg per day limit.
Sources like tea, cola soft drinks, energy drinks, chocolate and coffee ice cream can all contain caffeine. Caffeine also shows up in herbal products and over-the-counter drugs, including some headache, cold, and allergy remedies. So read labels carefully.
As a rough guide, a can of an energy drink like Red Bull or V has 80 mg of caffeine. Black and green tea have about 50 mg while cola drinks have 35 mg in a 375 mL can. If you enjoy dark chocolate, then you’ll find about 40 mg of caffeine in a 50 gram serve.
Cutting your caffeine habit
If your daily coffee ritual amounts to a lot more than 2 cups a day before you decided to try to conceive, then time is on your side to wind back your habit to make the transition easier and avoid some of the withdrawal symptoms, such as fatigue and headaches.
You might want to start by switching to a drink that’s half regular brew and half decaf. Or reduce the caffeine in homemade hot beverages by watering them down or brewing them for a shorter time. If you love to start your day with a cup of black tea, steeping your tea bag for one minute instead of five cuts the caffeine by as much as half.
Coffee at this stage is not on the avoid list during pregnancy, but it is one that at least for a short time in her life, a woman should make a concerted effort to keep her coffee addiction in check.
So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.
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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.