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Scientists examine the association between preconception maternal beverage intake and IVF outcomes, in the journal Fertility and Sterility.
Prof. Geraldine Hartshorne, Head of Clinical Faculty, Warwick Medical School, University of Warwick, said:
“For optimal fertility, being healthy is important. This includes not smoking, limiting drinking of alcohol, maintaining a healthy weight and having adequate exercise, sleep and a balanced diet that includes all food groups.
“It is exceptionally difficult to design studies that test lifestyle choices properly, because all of the choices are interlinked. For example, the decision to drink a sugary soda, which has more calories than a diet version, may be related to either gaining weight or expending more energy through exercise to stay lean. The choice of a sweet drink may also reflect a person’s other food choices and perhaps the overall balance of different types of carbohydrates, proteins, fats, vitamins, fibre and so on. Consequently, many different factors and individual differences that are not measured can greatly influence the results.
“This study has attempted to isolate sugary and caffeinated drink consumption from the rest of a person’s lifestyle in order to measure its association with IVF success. The authors found some association between sugary drinks and lower outcomes, however, the evidence is not very strong.”
Dr Jane Stewart, Secretary of the British Fertility Society and Consultant Gynaecologist at Newcastle Fertility Centre, said:
“This paper adds useful information to the discussion around diet and wellbeing in relation to fertility. Relating to live birth outcome the specific group concerned comprised 37 women drinking between 1.1 and 10 cups of soda per day. That is a very wide range and for those drinking large amounts might also reflect their overall eating habits that weren’t explored.
“The paper does not tell us that drinking occasional fizzy drinks will reduce IVF outcome for an individual.
“Interestingly caffeine (which is often cited as a problem) again did not appear to be a concern in this study.”
Dr Raj Mathur, member of the British Fertility Society, Consultant Gynaecologist at St Mary’s Hospital, Manchester, and Honorary Senior Lecturer at the University of Manchester, said:
“This is a well-designed prospective study with good patient numbers. It shows a correlation between the intake of sugared soda drinks and lower number of eggs retrieved at IVF as well as a lower chance of clinical pregnancy and live birth.
“The authors have not carried out any work on the mechanisms why this might be the case, although they provide some interesting and plausible hypotheses.
“One weakness of the paper is that patients may not recall accurately their beverage consumption. A further issue is that a large proportion of patients were not infertile, but having IVF for Pre-implantation Genetic Diagnosis to avoid genetic disease in the offspring; this may limit the generalisability of their data.
“However, the study does identify a potential correctable factor that may be reducing some patients’ chance of IVF success and should be taken note of by clinicians.”
Dr Ali Abbara, Senior Clinical Lecturer in Endocrinology, Imperial College London, and member of the Society for Endocrinology, said:
“This interesting study suggests that drinking too many sugary soda drinks may be associated with poorer outcomes following IVF treatment. These types of studies are very difficult to do and are prone to misinterpretation. People who drink sugary drinks may also have other detrimental habits for their health, such as a generally poor diet or smoking. They may also have a partner who also drinks sugary soft drinks, or have other unidentified risk behaviours, which could be the true reason for these findings.
“Although the researchers have tried very hard to collect this kind of information and correct for it in their statistical analysis, it can sometimes be difficult to do this fully. Whilst we still cannot be sure that sugary drinks are themselves to blame for the worse outcomes seen in this study, avoidance of sugary drinks is likely to be good for a woman’s health in general.”
Prof. Darren Griffin, Professor of Genetics, University of Kent, said:
“This is an Israeli-US collaborative study with a prospective design aimed to look at the effect of commonly taken drinks on IVF outcomes.
“The main outcome measures were IVF success (eggs retrieved, mature eggs retrieved, fertilisation, number of good quality embryos) looking mostly at caffeine and sugar (in fizzy drinks) intake. Put simply, the message is that (at least in the patient population that they studied) people that had a higher intake of sugared drinks fared worse, but there was nothing really to report in terms of caffeine intake.
“Given that the resultant health message would be ‘avoid sugary drinks during IVF’ and given that this is a reasonably good health message generally, it is probably worth making patients aware of it. The results are statistically significant but, perhaps more importantly, more than on average 1 fewer (mature) oocyte retrieved and, again on average, half a fertilised egg/good quality embryo less is a sufficiently large number to communicate to patients. At this stage, it is not certain that the sugar itself is the problem however the data is sufficiently notable to warrant further studies – a prospective randomised study in which patients are given unmarked cans (sugared and diet) might be the next way forward, perhaps applied in multiple centres.
“In the meantime, this study certainly gives food for thought, it seems unlikely that switching to water rather than sugary soda would have any detriment so I see no harm in recommending it to patients. The authors are clearly aware of the limitations of their study and how future studies might be addressed.”
Dr Ian Johnson, Nutrition researcher and Emeritus Fellow, Quadram Institute Bioscience, said:
“This is an interesting finding, but as is often the case, the observed association may just indicate that some other unmeasured factor in the diets or lifestyles of patients consuming high levels of sugary soda is the real cause of the impaired IVF. The authors propose some plausible mechanisms for an effect of sugar, but these could only be tested by further research. In the mean time it will certainly do no harm if women avoid sugary soft drinks whilst undergoing IVF treatment, but this study on its own is not strong enough to suggest that advice.”
Prof. Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said:
“This paper, like many others, simply reports an association and it cannot prove high sugary drink intake causes problems with IVF success. To do so would require a randomised trial. The more likely reality is that high sugary drink intake is associated with inferior IVF success by being a marker for an adverse lifestyle which could include poorer diets in general, and lower activity levels as well as other aspects like degree of smoking. Thus the claims by authors that “sugared beverages… may be a bigger threat to reproductive success….” is way too strong and proper trials need to address this. That noted, getting people to take less sugar-rich drinks is always welcome in general, especially if replaced by diet drinks or best by water, but not on the basis of this study alone.”
* ‘Association between preconception maternal beverage intake and in vitro fertilization outcomes’ by Ronit Machtinger et al. was published in Fertility and Sterility.
Declared interests
Dr Raj Mathur: “I should declare that I am an NHS Consultant and have a private practice, but am not aware of any relevant conflicts of interest in relation to this article.”
Prof. Darren Griffin: “No COI to declare.”
Dr Ian Johnson: “No declared interests.”
None others received.