Do you know what helps bees to remember which plants they would like to visit again? Yes, that's right, the answer is caffeine. According to scientists, who are definitely some of my favourite people, bees like to return to flowers which produce caffeine containing nectar. If you think that's an interesting fact, you can read all about it here, I suspect you are going to enjoy this blog post. Although caffeine is a relatively simple molecule (see it's structure below), it does have some pretty impressive properties and there is considerable debate about the impact of caffeine on pregnancy. The World Health Organisation recommends that pregnant women not exceed a daily caffeine intake of 200-300 mg. However, in constrast, a recent Cochrane Review concluded that there was insufficient evidence to determine whether restricting caffeine consumption improves pregnancy outcomes (see here). But I am sure you're not so interested in bees or pregnant ladies; what you really want to know is: will caffeine make your IVF cycle less likely to succeed? Well, you're in good company because so do I.
Let's go together now and take the third step on our research journey or, as I have affectionately called it, Operation Big Belly. As you may remember, we looked at the evidence that diet can impact an IVF cycle here, whether a drink or two will reduce your chances of having an IVF baby here, and, as usual, just a reminder that the ground rules can be found here.
So then, caffeine and IVF. Well, once again, I have spent a considerable amount of time searching on-line databases to provide you with the all the latest information. And, as usual, I have found very little data on the impact of lifestyle on IVF success. This time I was looking specifically for caffeine data and, frustratingly, I haven't found a larger data set than I dug up for the effect of diet or alcohol on IVF cycles. In fact, I have managed to only scrape together two studies. Still, two studies are better that none and it does give us something to get our teeth into.
The earliest study, led by Hillary Klonoff-Cohen, was conducted between 1993 and 1998 in Southern California. During the clinical trial, 221 couples, undergoing IVF or gamete intra-fallopian transfer (GIFT), were recruited to determine if there was a link between caffeine consumption and IVF outcome. The authors reported that, for women consuming caffeine from coffee, tea, soft drinks, cocoa drinks, or chocolate, the risk of miscarriage, not becoming pregnant and not achieving a live birth was significantly increased. There was, however, much better news for the boys: male caffeine consumption did not negatively affect sperm, embryo transfer rates, the chance of getting pregnant or pregnancy outcomes. But, and this is quite a big but, men's caffeine intake did correlate well with an increase in the number of multiples. So if you don't want to have twins......
You might not like the findings from that first study, and who could blame you, neither do I. But, let's remember, it is a very small study and only a lone study. Perhaps more recent data will give us better news.
The second study we are going to take a look at was conducted in the slightly more exotic location of Saudi Arabia. This time 619 women took part and all of them went through their first IVF cycle between 2002 and 2003. Unlike the majority of the studies we have examined, this study has something special; the lifestyle results are not only based on questionnaires completed by the patients but, in addition, the actual concentration of caffeine was measured in blood and, more excitingly, in follicular fluid. The study authors concluded that they could find no association between coffee and tea consumption, or the level of caffeine in serum, and pregnancy rates (yay, some good news at last). However, they did find a negative correlation, albeit a weak one, between tea drinking and the number of good embryos - the more tea you drink the fewer the good embryos. And there was also a link between high caffeine consumption and miscarriage. Sadly, the study didn't continue to assess the women for the next nine months, so we can't tell if caffeine would have impacted the live birth rate in those women.
So, let's sum up, we have one study that shows caffeine does negatively effect IVF cycles and one that indicates it probably doesn't. Oh, if only we had more data. Hang on, what's this? Ah, I am about to break Operation Big Belly's ground rules; I have found one more relevant study that was reported at a scientific meeting but has not been formally published. However, the meeting abstract and the subsequent press release are available on-line.
The study was a large one - this time we're in Denmark - and was presented last year to the European Society of Human Reproduction and Embryology (ESHRE). The researchers followed nearly 4000 women before and after their IVF cycles to find out if drinking coffee would result in lower pregnancy or live birth rates. Once all the data were collected, the investigators found that having up to four cups of coffee per day didn't really make any difference to the IVF outcome (yay, again), but having five or more coffees reduced the pregnancy rate by a whopping 50 percent and the live birth rate by, an equally staggering, 40 percent. Oh.
It seems that, at the moment with a very limited data set, heavy coffee consumption can reduce your chances of taking home a baby after IVF. Although, of course, it is possible that future larger studies, which I hope that some smart research group is working on right now, will show that caffeine doesn't really cause less women to become pregnant or babies to be born.
So, that's caffeine dealt with. What's coming up next? Well, in case you haven't figured it out already, the first phase of Operation Big Belly is dealing with consumption: we have looked at food, alcohol and caffeine. As I am not planning to tackle illegal drugs, the only thing left to look at is cigarette smoking. Ahhh, the evil weed. Until next time....
Thanks for this post. So helpful!
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