August 18, 2023

expert reaction to study on women’s adherence to healthy dietary patterns and outcomes of infertility treatment

A study published in JAMA Network Open looks at women’s adherence to healthy dietary patterns and outcomes of infertility treatment.

Dr Bassel Wattar, Consultant Obstetrician and Gynaecologist, Epsom and St Helier University Hospitals, said:

Does the press release accurately reflect the science?

“I could not access the press release.”

Is this good quality research?  Are the conclusions backed up by solid data?

“This study used routinely collected observational data on the dietary intake of patients undergoing assisted conception treatments (IVF, ICSI, and IUI). The quality of this type of data is often poor due to high recall bias when completing food frequency questionnaires. It is also important to consider the chance of performance and selection bias when analysing this type of data. While the findings are interesting, the conclusions made are a bit too strong considering the small size of the study (only 612 women which is relatively small compared to other dietary studies) and the high risk of bias.”

How does this work fit with the existing evidence?

“There is substantial evidence highlighting the importance of healthy eating and lifestyle intervention to optimise the outcome of assisted conception treatments among couples with subfertility. The benefits of Mediterranean diet have been translated across different domains in women’s health, however, top quality evidence from randomised trial remains a miss to confirm which type of diet is most effective in this cohort. This study is helpful to guide future research, but it would be too early to translate its findings into clinical practice.”

Have the authors accounted for confounders?

“The authors did use good quality methodology and have performed Multivariable adjusted models to adjust for potential confounders. However, given the retrospective and observational nature of the data, several hidden confounders could have been missed which could significantly impact the validity of this study.”

Are there important limitations to be aware of?

“Primarily there are limitations due to the type, quality, and size of the data. Also, the population selected is slightly of advanced maternal age (35 median). We know the risk of miscarriage is >25% in this population due to reduced oocyte quality. As such, the risk of miscarriage depicted could be entirely due to chance and this sample is not representative of the whole population.”

What are the implications in the real world?

“The study is helpful to highlight the potential benefits of different dietary regimes and lifestyle intervention. At this stage, I would consider these findings only helpful to guide future research and too early to adopt them into clinical practice.”

Is there any over-speculation?

“The reduction in the risk of miscarriage with the AHA diet could be entirely due to chance.”

Is this an association or causation? Could there be other reasons for the association?

“It is an association. We could only establish causation in a well powered large scale multi-centre randomised trial.”

Dr Helen O’Neill, Programme Director, Reproductive Science and Women’s Health, University College London (UCL), said:

“None of the dietary patterns examined were associated with the probability of live birth however the findings suggest that preconception adherence to the AHA diet pattern was

inversely associated with total and clinical pregnancy loss in women who achieved pregnancy during the course of infertility treatment with IUI or IVF. Unfortunately, we don’t seem to have enough data on individuals’ medical history and if any individuals had experienced recurrent pregnancy loss which could have influenced these outcomes. 

“The AHA dietary pattern was richest in fish (a great source of omega-3 fatty acids), whole grains and folic acid which we already know from current research to be important in preconception and because the diets were assessed prior to undergoing treatment this helps to support the importance of preconception adherence to fertility promoting foods, however, the limitation of the study is that they failed to collect the data on what the participants diets were once they were undergoing treatment which could have influenced outcomes.

“In related research this year that looked at the preconception period and miscarriage risk, a recent systematic review and meta-analysis could not define if pre-defined dietary types, such as the Mediterranean Diet or Fertility Diet could also be linked to miscarriage risk. Therefore, it is evident we need further interventional studies to accurately assess the effectiveness of periconception dietary modifications on miscarriage risk as well as research that could accurately estimate how effective a change in diet could be on risk of pregnancy loss. 

“Like many dietary studies, because of the observational nature of the study, it is difficult to determine causality, however, the authors stated that they included and compared the largest number of dietary patterns compared to date, which is promising going forward in future studies when considering other public health recommended diets and their positive effects on fertility in addition to general health. 

“The study also included a predominantly white population which is therefore not reflective of a diverse population.”

Prof Ying Cheong, Professor of Reproductive Medicine and Honorary Consultant in Reproductive Medicine and Surgery, University of Southampton, said:

“For patients with infertility, we have not found the perfect diet to better live birth. The researchers studied women taking 8 types of diets and looked at their fertility treatment outcomes. They confirm the importance of having a healthy preconception diet, one which prioritizes eating fruits and vegetables, and limiting food with high sugars, processed meat and saturated fats, which is associated with a lower likelihood of miscarriages. Interestingly, they did not observe an association with increased live birth with any of these diets.

“The researchers studied women taking 8 different diets and if any of these are associated with better fertility treatment outcomes. The study was conducted over 12 years including 612 women in the analysis; participants completed a mixture of 1572 fertility treatments (in vitro fertilisation and intrauterine insemination). The major drawback of this study is its observational nature, which means they observed an association but we do not know if these diets directly cause lower miscarriage rate. They have only asked the participants at one time point about their diet, and so it is not possible to deduce if dietary patterns have changed. As it is also conducted in one fertility centre, on fertility patients, the results cannot be generalised to the entire population. Furthermore, diet is only one aspect of health.

“Generally speaking, doctors should be advising women who are trying for a pregnancy to consume a healthy preconception diet. This study provides some evidence that a preconception diet emphasising eating fresh fruits and vegetables, whole grains, fish and shellfish, and nuts and legumes but limiting sugar-sweetened beverages, sodium, processed meat, and saturated fats, is associated with a lower miscarriage rate.

“The observation that women on all the diets apart from those on plant-based diet (PBD) had a lower likelihood of miscarriage is interesting. Many people are now choosing to go on plant-based diet. More research is needed on the impact of PBD on reproduction outcomes.”

Dr Duane Mellor, Registered Dietitian and Senior Lecturer, Aston Medical School, Aston University, said:

“This paper looked at the associated risk between eight different scores which can be used to assess dietary quality and the likelihood of a successful pregnancy following infertility treatment. As such it can only assess a potential association and therefore cannot and does not show any causal link between dietary intake and having a successful pregnancy following fertility treatment.

“It also, as it focuses on couples undergoing treatment for some form of infertility, and therefore it does not provide any information about dietary patterns and human fertility in general.

“As a study using data from a single clinic, it is also very difficult to take any meaning from this study when trying to apply it to different populations. 

“It is also challenging as it only suggests an association of an inverse relationship between American Heart Association (AHA) diet score and risk of a pregnancy loss when both types of infertility treatment are combined. This suggests that women whose reported diet more closely matched the AHA diet more closely had an associated lower risk of pregnancy loss.

“Although they controlled for some variables, including age (noting that women undergoing infertility treatment are likely to be slightly older), BMI and energy intake. It was not able to show an association between any of the dietary pattern scores and type of infertility treatment, possibly as it was only a single clinic study, it did not have a big enough number of participants to see if IVF or Intrauterine insemination might have affected any associated risk of any of the particular dietary patterns. Also, as the researchers chose to test eight different diet scores, it only found a clear association for the AHA score when combining both types of treatment, so although pre-determined diet scores were used, there seemed to be no clear hypothesis or theory that they started with of which diet might be associated with the lowest risk of losing a pregnancy following infertility treatment.

“It is important that women should not feel guilty about any of their individual dietary choices during pregnancy, as it can be difficult to eat healthily especially when struggling with some of the problems associated with pregnancy such as morning sickness. It is also important when planning pregnancy including following infertility treatment that folic acid supplements are taken to reduce the risk of neural tube defects as well as a diet that is varied to include key nutrients during pregnancy including iodine. So, when planning a pregnancy, it is important that both parents should consume a varied diet (including folic acid supplements) based on plenty of vegetables, fruit, nuts, seeds and pulses (beans, peas and lentils), a modest amount of meat, poultry and fish with dairy foods and abstaining from alcohol and foods which may be a risk during pregnancy e.g., unpasteurised dairy products, pate and unwashed salad etc.”

‘Women’s Adherence to Healthy Dietary Patterns and Outcomes of Infertility Treatment’ by Albert Salas-Huetos et al. was published in JAMA Network Open at 16:00 UK Time Friday 18 August 2023.

DOI: 10.1001/jamanetworkopen.2023.29982

Declared interests

Dr Bassel Wattar: “No conflict of interest to disclose.”

Dr Helen O’Neill: “I am CEO and Founder of Hertility Health.”

Prof Ying Cheong: “I am the Medical Director of Complete Fertility.”

Dr Duane Mellor: “No conflicts of interest to declare.”

For all other experts, no reply to our request for DOIs was received.