Assessing the influence of preconception diet on female fertility: a systematic scoping review of observational studies

Body Composition and Dietary Intake of Women Attending an Infertility Clinic-Polish Observational Study

BACKGROUND AND OBJECTIVES

We aimed to assess the body composition and dietary intake of female patients attending one of the Polish infertility clinics. Additionally, we evaluated if there were any relationships between dietary intake and body composition parameters.

METHODS

The study involved 51 women who met the inclusion criteria. For the nutritional assessment, we used 3-day dietary records. Weight, height, waist and hip circumferences, and body composition were assessed. The participants were divided into three groups, with low (I, n = 12), normal (II, n = 27), and high (III, n = 12) fat tissue content, and then compared in terms of dietary intake.

RESULTS

The lowest protein intake per kilogram of body weight was observed in group III (p < 0.001). In group I, we reported the highest consumption of plant protein in general (p = 0.03) and per kg of body weight (p < 0.001). Higher protein intake per kg body mass was associated with lower values of BMI (r = -0.681; p < 0.001), fat mass (r = -0.641; p < 0.001), waist-hip ratio (r = -0.391; p = 0.005), and abdominal fat index (r = -0.653; p < 0.001).

CONCLUSIONS

Our findings suggest that targeted nutritional counseling focused on optimizing protein intake and emphasizing plant-based sources may improve body composition and potentially support fertility outcomes in women undergoing infertility treatment.

Metabolic Mechanisms Underlying the Association Between the Profertility Diet and In Vitro Fertilization End Points

BACKGROUND

The profertility diet is a dietary pattern composed of nutrients and foods most consistently associated with in vitro fertilization (IVF) end points in women.

OBJECTIVES

We examined the potential biological mechanisms underlying the association between adherence to a profertility diet and IVF end points using high-resolution metabolomics.

METHODS

Among 120 women who underwent an autologous oocyte IVF cycle (2007-2015) in Northeast United States, we collected a serum sample during controlled ovarian stimulation and a follicular fluid sample on the day of oocyte retrieval. Women completed a food frequency questionnaire upon enrollment into the study to examine adherence to the profertility diet pattern. Liquid chromatography with high-resolution mass spectrometry was used for untargeted metabolomic analysis of biospecimens. We identified metabolic features (and enriched biological pathways) associated with the profertility diet and 2 IVF end points, live birth and clinical pregnancy, via a meet-in-the-middle approach.

RESULTS

In the follicular fluid metabolome, vitamin D-3 metabolism was associated with adherence to the profertility diet pattern and live birth. Additionally, vitamin D-3 metabolism, vitamin B-6 metabolism, and bile acid biosynthesis were associated with both adherence to the profertility diet pattern and clinical pregnancy. In the serum metabolome, only tryptophan metabolism was associated with adherence to the profertility diet pattern and live birth. We confirmed the chemical identity of a metabolite with level 1 evidence, 4-pyridoxate, which was higher in the serum and follicular fluid among women with stronger adherence to the profertility diet pattern and among women with a live birth.

CONCLUSIONS

The beneficial association between adherence to the profertility diet and IVF outcomes may be mediated through vitamin D-3 metabolism, vitamin B-6 metabolism, and bile acid biosynthesis in the follicular fluid and tryptophan metabolism in the serum. These results provide new insight in the important biological pathways underlying a dietary pattern providing optimal fertility benefits to women.

Barriers and enablers to a healthy lifestyle in people with infertility: a mixed-methods systematic review

BACKGROUND

While there is a recognized role of optimizing lifestyle (diet and physical activity) behaviours in the management of infertility, the best practice remains unknown and factors influencing the lifestyle of people with infertility are not well understood.

OBJECTIVE AND RATIONALE

This systematic review evaluated barriers and enablers to a healthy lifestyle in people with infertility, from the perspectives of people with infertility and health professionals, in order to inform optimal behavioural change strategies.

SEARCH METHODS

Ovid MEDLINE(R), PsycINFO, EMBASE, EBM Reviews, and CINAHL were searched from inception to 28 August 2023. Eligible studies were qualitative and quantitative primary studies that explored barriers and/or enablers to lifestyle for infertility management. Quality assessment was performed using the Centre for Evidence-Based Management Critical Appraisal of a Survey Tool and the Critical Appraisal Skills Programme Qualitative Checklist. Data were analysed by thematic analysis with themes mapped to the Capability, Opportunity, Motivation and Behaviour (COM-B) model and Theoretical Domains Framework (TDF).

OUTCOMES

After screening 12 326 abstracts and 99 full-texts, 27 studies were included (12 quantitative, 6 qualitative and 9 mixed-methods) with 22 studies of women with infertility (n = 2524), 11 studies of men with infertility (n = 1407), and 6 studies of health professionals (n = 372). We identified barriers and enablers relating to capability (e.g. strategies for behaviour change), opportunity (e.g. limited time, resources, and money), and motivation (e.g. interplay between lifestyle and emotional state). Based on the identified themes, suggested intervention components to integrate into lifestyle management of infertility include facilitating development of self-management skills to support lifestyle change (e.g. self-monitoring, action planning, and goal setting) and incorporating mental health strategies (e.g. providing information about the benefits of healthy lifestyle behaviours for mental health and encouraging patients to reframe healthy lifestyle behaviours as self-care strategies).

WIDER IMPLICATIONS

The findings have identified important factors that influence lifestyle management in people with infertility and have suggested relevant intervention components to consider when designing interventions. Given the paucity of qualitative studies identified, more research is needed to further understand the complex and interacting factors that shape lifestyle during the fertility journey.

Association of ambient PM2.5 and its components with in vitro fertilization outcomes: The modifying role of maternal dietary patterns

Despite the associations of dietary patterns and air pollution with human reproductive health have been demonstrated, the interaction of maternal preconception diet and PM2.5 and its components exposure on in vitro fertilization (IVF) treatment outcomes has not been investigated. A total of 2688 couples from an ongoing prospective cohort were included. Principle component analysis with varimax rotation was performed to determine dietary patterns. One-year and 85-day average PM2.5 and its components exposure levels before oocyte retrieval were estimated. Generalized linear regression models were conducted to assess the association of dietary patterns and PM2.5 and its components exposure with IVF outcomes. Interactive effects of dietary patterns on the association between PM2.5 and its components and IVF outcomes were evaluated by stratified analyses based on different dietary patterns. A positive association between the "Fruits-Vegetables-Dairy" pattern and normal fertilization (p-trend = 0.009), Day 3 available embryos (p-trend = 0.048), and top-quality embryos (p-trend = 0.041) was detected. Conversely, women with higher adherence to the "Puffed food-Bakery-Candy" pattern were less likely to achieve Day 3 available embryos (p-trend = 0.042) and top-quality embryos (p-trend = 0.030), clinical pregnancy (p-trend = 0.049), and live birth (p-trend = 0.020). Additionally, increased intake of animal organs and seafood improved the odds of live birth (p-trend = 0.048). Exposure to PM2.5, SO42-, organic matter (OM), and black carbon (BC) had adverse effects on embryo development and pregnancy outcomes. Furthermore, our findings indicated that the effects of PM2.5 components exposure on normal fertilization and embryo quality were modified by the "Grains-Tubers-Legumes". Moreover, moderate intake of animal organs and seafood appeared to attenuate the effect of NO3- and NH4+ on the risk of early abortion. Our findings provide human evidence of the interaction between dietary patterns and PM2.5 exposure on IVF outcomes during preconception, implicating the potential for dietary interventions in infertile women to improve reproductive outcomes under conditions of unavoidable ambient air-pollutant exposure.

Association between tea, coffee and caffeine consumption and risk of female infertility: a cross-sectional study

OBJECTIVES

To explore the association between tea, coffee, and caffeine consumption and the risk of female infertility.

METHODS

We analyzed data from 2099 females aged 18 to 44 years, participating in the National Health and Nutrition Examination Survey (NHANES) 2013-2018. We used generalized linear models (GLM) and generalized additive model (GAM) to investigate the dose-response relationship between the tea, coffee, and caffeine consumption and infertility, adjusting for potential confounders.

RESULTS

A non-linear relationship was detected between tea consumption and infertility and the inflection point was 2 cups/day. On the right side of the inflection point, we did not detect a significant association. However, on the left side, we found a negative relationship between tea consumption and infertility (OR: 0.73; 95% CI: 0.57 to 0.93; P = 0.0122). Meanwhile, our study found no significant association between coffee (0.96, 0.81 to 1.13, P = 0.6189) or caffeine consumption (1.15, 0.93 to 1.42, P = 0.2148) and female infertility.

CONCLUSIONS

Tea consumption was non-linearly associated with infertility, whereas no significant associations were found between coffee, caffeine consumption and infertility.

Nutritional and exercise interventions to improve conception in women suffering from obesity and distinct nosological entities

Infertility among women, particularly those living with obesity, presents a multifaceted challenge with implications for reproductive health worldwide. Lifestyle interventions, mainly focusing on weight loss, have emerged as promising strategies to improve fertility outcomes in this population. This review aims to explore the effectiveness of various lifestyle interventions, encompassing dietary modifications and exercise regimens, in enhancing fertility outcomes among women with obesity and associated conditions such as polycystic ovary syndrome, congenital adrenal hyperplasia, type 2 diabetes mellitus, premenopause, hypothyroidism and eating disorders. Methodology of study search encompass a broad spectrum, ranging from interventions targeting weight management through slow or rapid weight loss to dietary approaches emphasizing whole food groups, specific nutrients, and dietary patterns like low-carbohydrate or ketogenic diets, as well as the Mediterranean diet. By synthesizing existing findings and recommendations, this review contributes to the understanding of lifestyle interventions in addressing infertility, with an emphasis on the population of women of reproductive age with excess weight and known or unknown infertility issues, while promoting their integration into clinical practice to optimize reproductive health and overall well-being.

Assessing the influence of preconception diet on male fertility: a systematic scoping review

BACKGROUND

The last decade has seen increased research on the relationship between diet and male fertility, but there are no clearly defined nutritional recommendations for men in the preconception period to support clinical fertility outcomes.

OBJECTIVE AND RATIONALE

The purpose of this scoping review is to examine the extent and range of research undertaken to evaluate the effect(s) of diet in the preconception period on male clinical fertility and reproductive outcomes.

SEARCH METHODS

Four electronic databases (MEDLINE and EMBASE via Ovid, CAB Direct, and CINAHL via EBSCO) were searched from inception to July 2023 for randomized controlled trials (RCTs) and observational studies (prospective/retrospective, case-control, and cross-sectional). Intervention studies in male participants or couples aiming to achieve dietary or nutritional change, or non-intervention studies examining dietary or nutritional components (whole diets, dietary patterns, food groups or individual foods) in the preconception period were included. Controls were defined as any comparison group for RCTs, and any/no comparison for observational studies. Primary outcomes of interest included the effect(s) of male preconception diet on clinical outcomes such as conception (natural or via ART), pregnancy rates and live birth rates. Secondary outcomes included time to conception and sperm parameters.

OUTCOMES

A total of 37 studies were eligible, including one RCT and 36 observational studies (prospective, cross-sectional, and case-control studies; four studies in non-ART populations) published between 2008 and 2023. Eight reported clinical outcomes, 26 reported on secondary outcomes, and three reported on both. The RCT did not assess clinical outcomes but found that tomato juice may benefit sperm motility. In observational studies, some evidence suggested that increasing fish or reducing sugar-sweetened beverages, processed meat or total fat may improve fecundability. Evidence for other clinical outcomes, such as pregnancy rates or live birth rates, showed no relationship with cereals, soy and dairy, and inconsistent relationships with consuming red meat or a 'healthy diet' pattern. For improved sperm parameters, limited evidence supported increasing fish, fats/fatty acids, carbohydrates and dairy, and reducing processed meat, while the evidence for fruits, vegetables, cereals, legumes, eggs, red meat and protein was inconsistent. Healthy diet patterns in general were shown to improve sperm health.

WIDER IMPLICATIONS

Specific dietary recommendations for improving male fertility are precluded by the lack of reporting on clinical pregnancy outcomes, heterogeneity of the available literature and the paucity of RCTs to determine causation or to rule out reverse causation. There may be some benefit from increasing fish, adopting a healthy dietary pattern, and reducing consumption of sugar-sweetened beverages and processed meat, but it is unclear whether these benefits extend beyond sperm parameters to improve clinical fertility. More studies exploring whole diets rather than singular foods or nutritional components in the context of male fertility are encouraged, particularly by means of RCTs where feasible. Further assessment of core fertility outcomes is warranted and requires careful planning in high-quality prospective studies and RCTs. These studies can lay the groundwork for targeted dietary guidelines and enhance the prospects of successful fertility outcomes for men in the preconception period. Systematic search of preconception diet suggests that increasing fish and reducing sugary drinks, processed meats and total fat may improve male fertility, while consuming healthy diets, fish, fats/fatty acids, carbohydrates and dairy and reducing processed meat can improve sperm health.

Food, nutrition, and fertility: from soil to fork

Food and nutrition-related factors, including foods and nutrients consumed, dietary patterns, use of dietary supplements, adiposity, and exposure to food-related environmental contaminants, have the potential to impact semen quality and male and female fertility; obstetric, fetal, and birth outcomes; and the health of future generations, but gaps in evidence remain. On 9 November 2022, Tufts University's Friedman School of Nutrition Science and Policy and the school's Food and Nutrition Innovation Institute hosted a 1-d meeting to explore the evidence and evidence gaps regarding the relationships between food, nutrition, and fertility. Topics addressed included male fertility, female fertility and gestation, and intergenerational effects. This meeting report summarizes the presentations and deliberations from the meeting. Regarding male fertility, a positive association exists with a healthy dietary pattern, with high-quality evidence for semen quality and lower quality evidence for clinical outcomes. Folic acid and zinc supplementation have been found to not impact male fertility. In females, body weight status and other nutrition-related factors are linked to nearly half of all ovulation disorders, a leading cause of female infertility. Females with obesity have worse fertility treatment, pregnancy-related, and birth outcomes. Environmental contaminants found in food, water, or its packaging, including lead, perfluorinated alkyl substances, phthalates, and phenols, adversely impact female reproductive outcomes. Epigenetic research has found that maternal and paternal dietary-related factors can impact outcomes for future generations. Priority evidence gaps identified by meeting participants relate to the effects of nutrition and dietary patterns on fertility, gaps in communication regarding fertility optimization through changes in nutritional and environmental exposures, and interventions impacting germ cell mechanisms through dietary effects. Participants developed research proposals to address the priority evidence gaps. The workshop findings serve as a foundation for future prioritization of scientific research to address evidence gaps related to food, nutrition, and fertility.

Dietary Strategies to Reduce Triglycerides in Women of Reproductive Age: A Simulation Modelling Study

Many women of reproductive age have poor diet quality and are at higher risk of chronic diseases such as diabetes. Triglycerides are a critical risk factor for chronic diseases, and although they can be influenced by diet, there are minimal dietary intervention studies identifying key foods/food groups that reduce triglycerides. We performed data simulation modelling to estimate the potential reductions in fasting triglycerides that could be achieved by different dietary strategies in reproductive age women. The model was created using data from the 2011-2013 Australian Health Survey and incorporated various factors such as demographics, nutrient intake, and plasma biomarkers. Multiple linear regression analysis was conducted to estimate triglyceride levels, considering nutrient intake and pre-determined covariates. Dietary scenarios were developed, reducing the consumption of processed/ultra-processed foods, while increasing the intake of minimally processed foods like fruits, vegetables, fish, and nuts. A total of 606 women were included. Reducing processed foods by 50% plus increasing intakes of fruits (75-225 g/day), vegetables (75-225 g/day), or nuts (10-40 g/day) decreased triglycerides by up to 4.3%. Additionally, incorporating 80 g/day of omega 3 fish (>800 mg long-chain omega 3/100 g) decreased triglycerides by 8.2%. The clinical relevance of lowering triglycerides for cardiometabolic disease management should be tested in dietary intervention studies in women.