Diet and the Reproductive System

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15 Factors That Affect a Woman's Fertility
Abstract This article reviews nutrition-related issues affecting women and their reproductive health. Publications that focused on reproductive performance and specific lifestyle factors were reviewed. Other potential confounding variables such as frequency of intercourse were not considered. Therefore, it is best for any woman of childbearing age to be especially careful to get enough folic acid each day. These results are particularly significant as the women required ART treatment because of male factor infertility and therefore reflected a relatively normal population with few of them requiring stimulation. Thiamine is an important part of your nervous system. When a plaque becomes very advanced, it can completely stop blood from passing through, which is what happens in a heart attack.

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An OR of 1. A study of couples from 10 European countries also found a strong association between female smoking and subfecundity Bolumar et al. A systematic review reported that 12 out of 13 studies demonstrated a negative effect of female smoking on conception Hughes and Brennan, Republished from Augood et al. A meta-analysis of nine studies found an OR of 0.

Another meta-analysis reported that almost twice as many IVF cycles were needed to achieve pregnancy for smokers compared with non-smokers Feichtinger et al. These effects were observed against a cycle-specific pregnancy rate of Similarly, a study of women undergoing IVF found that smokers did not respond as well to stimulation as non-smokers, fertilization was lower and none of the regular smokers became pregnant Crha et al.

The risk increased with each year of smoking. A recent review of lifestyle habits and IVF concluded that there was compelling evidence of the negative effect of smoking on IVF outcome Klonoff-Cohen, There is also emerging evidence of adverse effects on reproduction associated with passive smoking.

A recent study of women undergoing IVF found that fertilization rates were similar for smokers, passive smokers and non-smokers, whereas pregnancy rates were significantly decreased for smokers Smoking has been shown to adversely affect the chance of pregnancy from ART, with results of studies suggesting that smokers require nearly twice as many IVF cycles to conceive as non-smokers Feichtinger et al.

Obesity is associated with a range of adverse health consequences. Widely recognized are the increased risks of cardiovascular disease, diabetes and some cancers.

Obesity and low body weight can impact on reproductive function by causing hormone imbalances and ovulatory dysfunction. The effect of adolescent BMI at age 18 as a predictor of ovulatory infertility was examined.

Compared to women with a BMI of 20— The risk of infertility with increasing BMI was apparent for women with and without polycystic ovarian disease. Relative risk of infertility by BMI at age Republished from Rich-Edwards et al. Supporting these findings is a study that investigated lifestyle factors in pregnant women. Another large study of women from five European countries Bolumar et al. Obesity has been shown to decrease the probability of pregnancy for women undergoing ART.

A large Australian study of women who underwent ART found that pregnancy rates were halved for very obese women in comparison with women with a normal BMI Wang et al. Further evidence was found in a study of women undergoing IVF. After adjusting for age and the number and quality of embryos, the chance of pregnancy was halved for overweight women OR 0. The distribution of body fat also impacts on reproductive performance but the mechanism for this effect is unclear Norman et al.

A prospective study of apparently normal women undergoing donor insemination Zaadstra et al. These results are particularly significant as the women required ART treatment because of male factor infertility and therefore reflected a relatively normal population with few of them requiring stimulation.

This contrasts with women with a normal BMI of The lower rate in the obese group was mainly due to an increased risk of early pregnancy loss. High BMI in women has also been associated with other adverse pregnancy outcomes such as gestational diabetes and hypertension Michlin et al. The evidence for the effects of weight on reproduction from observational studies has given rise to a number of significant intervention studies. Lifestyle modification programmes that include exercise have been shown to assist women to lose weight, improve their fitness, increase psychological well-being and improve reproductive functioning Clark et al.

The women in this study attended a weekly programme for 6 months that included an exercise component and education relating to diet and psychological issues associated with being overweight.

Although the number of women taking part in the study was relatively low, the positive effects of participating in the programme were outstanding.

On average, the women lost Of the 67 women who completed the study, Eating a healthy diet consisting of appropriate composition and caloric intake is fundamental to maintaining a state of optimum physical and psychological health.

It is also important in preventing diseases such as obesity, cardiovascular disease, diabetes, osteoporosis and some cancers. Diet mediates body weight and composition and should be considered fundamental to reproduction. However, although a link has been demonstrated between maternal nutritional status and adverse pregnancy outcomes Fall et al.

Early pregnancy is a vulnerable period for embryo and fetal development and the environment at the time of conception can impact on the developing embryo and subsequent long-term health of the child Chapin et al.

Studies directly relating dietary components to the chance of conceiving are sparse in humans. However, there is strong evidence that a well-balanced healthy diet is beneficial for general well-being and optimum body functioning Sanders, and it has been suggested that diet before pregnancy may influence fetal well-being Moore and Davies, Therefore, reproductive performance should be positively influenced by the consumption of a healthy varied diet.

Regular exercise affects an individual's general health and well-being and probably provides some protection from obesity, cardiovascular disease, hypertension, diabetes, osteoporosis and psychological stress.

Research in relation to physical fitness and reproduction is primarily focused on athletes rather than women who have a moderate level of fitness. However, there was no association with moderate exercise. This is in contrast to the Clark et al. The women in this study underwent a 6-month lifestyle modification programme that included a weekly group fitness component and at least two further exercise sessions per week.

In addition to losing weight, each participant's fitness level improved. Exercise increases insulin sensitivity, which improves ovarian function and the chance of conception Norman and Clark, Exercise during pregnancy has also been reported to increase maternal well-being Morris and Johnson, The overall physical, emotional and increased general well-being benefits of being physically fit are well documented Berlin and Colditz, ; Sandvik et al.

However, there is a need for further research regarding the effects that moderate and low-level exercise may have on reproductive performance. It is reasonable to assume that the general health benefits associated with moderate levels of exercise and the consumption of a well-balanced diet would also apply to fertility. These lifestyle practices should therefore be recommended to couples attempting pregnancy. Further research is needed to clarify the effect that exercise may play on reproductive performance.

The above evidence associated with age, smoking and weight shows that there is strong substantiation of an adverse association between these lifestyle factors and the risk of impaired fertility.

Other lifestyle factors such as psychological stress, caffeine and alcohol consumption and environmental pollutants may impact on reproductive health and adversely affect fertility.

However, so far, the evidence is limited and not consistent across studies. Psychological stress may reduce female reproductive performance in various ways. The autonomic nervous system, the endocrine and immune systems have all been implicated Hjollund et al. Given that infertility and ART treatment are associated with stress Hammarberg et al. A randomized controlled trial compared a cognitive behavioural group, a support group and a control in women attempting to conceive for 1—2 years both naturally and from ART treatment Domar et al.

Women were randomized into one of three groups: The first intervention group was a cognitive behavioural group where participants were taught relaxation and cognitive restructuring techniques. They were also given information about nutrition and exercise. In light of the evidence above, providing this type of information may be a potential confounder of a direct effect on psychological factors. The second intervention group was a support group.

Participants were encouraged to discuss issues such as infertility treatment and their emotional feelings, followed by a more structured information session on a topic such as the impact of infertility on self-esteem.

The women also met with a psychologist twice during the year of follow-up for testing of stress levels. An observational study Hjollund et al. Couples were followed for six menstrual cycles. Decreased conception was associated with women who reported being most stressed The effects seen in the general population carry over to women undergoing ART treatment where there is also some evidence of a negative effect of increased levels of stress and IVF success Thiering et al.

A randomized controlled trial of 60 couples attending a Turkish Hospital for their first IVF treatment Terzioglu, found a statistically significant association between providing counselling and support to couples and increased pregnancy rates. A nurse who worked closely with the couples throughout the most stressful periods provided the intervention.

The nurse gave couples detailed information about their treatment, made daily contact with the couple from the commencement of stimulation until embryo transfer and was present at oocyte collection and embryo transfer.

Standard care was provided to the control group. Three standard psychological tests were used to collect data at the beginning of the treatment cycle and 4—5 days after embryo transfer.

Effects of counselling and support on ART pregnancy rates. Republished from Terzioglu with permission. There have been several observational studies to assess stress levels and associations with treatment outcome. An association between stress levels prior to a treatment cycle and treatment outcomes was found Klonoff-Cohen et al.

This study examined the effect of different types of stress on a range of outcome measures including oocytes retrieved, fertilization, pregnancy and live birth. Stress was assessed using standardized psychological tests that were administered prior to treatment and during treatment.

The chance of pregnancy and live birth delivery was decreased with increasing stress measures. The number of oocytes fertilized also decreased with increased stress. A prospective study conducted in Belgium of 98 women undergoing IVF used standardized psychometric questionnaires administered prior to commencement of the treatment cycle to assess depression and coping skills Demyttenaere et al. The study found an increase in negative emotions in the group that did not become pregnant.

A recent study of Danish couples Boivin and Schmidt, examined the effects of infertility-related stress on men and women and pregnancy after 1 year.

The data were controlled for potential confounders of age and length of infertility. A small increase in stress in women was associated with poorer treatment outcome, but not for men. Overall stress scores for women in the no success group were The small difference in means and wide scatter of the data may illustrate the difficulty of quantifying stress.

A Dutch study attempted to use biochemical markers of stress during IVF treatment as well as reported stress Smeenk et al. Higher levels of adrenalin were found at stressful time points in treatment oocyte retrieval and embryo transfer in women who did not become pregnant, compared with those who did become pregnant who also showed higher levels of noradrenalin at the time of embryo transfer. This study was blighted by missing data including the loss of urine samples. Several other studies have found stress to reduce pregnancy rates following ART treatment Thiering et al.

Distribution of waiting time to first pregnancy TTP in months by coffee drinking habits and caffeine intake of women from Denmark, Germany, Italy, Poland and Spain, August to February Republished from Bolumar et al. Other studies have found no relationship between the psychological status of women and the outcome of ART treatment Harlow et al. On balance, reported studies support an association between increased levels of psychological stress and impaired reproductive performance.

The level of precision in determining a cause — effect relationship is low because the major measurements of stress are subjective and there is lack of consensus in defining and measuring stress levels. The stimulant properties of caffeine have led to its widespread use as a beverage coffee, tea and soft drinks and some foods such as chocolate. Its consumption has been reported to prolong the time to pregnancy; although the mechanism for this is unclear, caffeine may affect female reproduction by targeting ovulation and corpus luteal function through alterations to hormone levels Klonoff-Cohen et al.

The consumption of caffeine has been associated with reduced fecundity in the general population. A prospective study of women attempting pregnancy found strong evidence of a reduced chance of pregnancy with increasing caffeine consumption Wilcox et al. The women were reviewed at enrolment and again at 3 and 6 months and their consumption of coffee, tea and soft drinks were recorded. The frequency of interviews allowed accurate recall of their caffeine consumption. Daily information was also recorded regarding menstrual bleeding and intercourse until a pregnancy was confirmed.

The data were adjusted for variables of age, frequency of intercourse, smoking, weight and age at menarche. Women who consumed less than one cup of coffee were twice as likely to become pregnant compared with the moderate coffee drinkers, with the risk of failing to become pregnant increasing with higher consumption. Most other studies rely on the collection of retrospective data after the period of caffeine consumption leaving them open to recall bias.

After adjusting for potential confounders of age, smoking, the use of contraceptives and country, the risk of delayed conception with large amounts of caffeine consumption remained. A study of pregnant women relied on interviews about their consumption of tea, coffee and cola between the time of conception and the date of interview Hatch and Bracken, The assumption was made that pre-pregnancy levels of caffeine consumption were consistent with levels during pregnancy.

However, with the achievement of pregnancy, women change many habits and caffeine consumption during pregnancy may not be the same as levels at the time of conception.

Coffee aversion in pregnancy is frequently associated with nausea. Other potential confounding variables such as frequency of intercourse were not considered. A study of women collected information about caffeine consumption coffee, tea and cola during the first month of pregnancy Stanton and Gray, Compared with non-smokers who did not consume caffeine, non-smoking women who drank more than three cups of coffee a day had a 2.

Predictably, smoking reduced the chance of pregnancy, but the effect of caffeine was only found in non-smokers. This study again makes the assumption that levels of consumption remain consistent before and during pregnancy, which may lead to misclassification.

This raises the possibility that caffeine consumption reflects a particular lifestyle that may include a number of confounding factors, of which smoking may be just one.

There are also studies that have found no association between caffeine consumption and fecundity Joesoef et al. Changes were integrated into each menstrual cycle by date of interview and averaged over the cycle. Caffeine consumption has also been associated with other causes of infertility including tubal factors and endometriosis Grodstein et al. A meta-analysis Fernandes et al. However, not all studies have found an association between caffeine consumption and spontaneous abortion Mills et al.

High levels of caffeine consumption during pregnancy has also been associated with an increased risk of stillbirth Wisborg et al. However, the concept of reverse causation due to unrecognized fetal problems may explain why women continued to drink large quantities of coffee during pregnancy. The evidence leans towards an association between the consumption of caffeine particularly at high levels and reproductive performance, although most studies have relied on data being collected retrospectively which is subject to recall bias.

There are fewer studies examining the effect of caffeine on the ART population. The women and their male partners completed questionnaires at different time points during their treatment regarding their caffeine intake and other factors. They were asked about consumption of a range of caffeine containing products: Caffeine consumption during treatment was not related to oocyte retrieval, fertilization, embryo transfer or pregnancy.

There are potential limitations to this study, including the difficulty in accurately recording exact consumption of caffeine and the relatively small numbers of live births. Alcohol is a known teratogen Randall, ; Chaudhuri, and its consumption has been reported to decrease fertility, although the level of consumption associated with risk is unclear. Alcohol consumption at the extreme level is known to be dangerous to the unborn child Astley et al.

The mechanisms by which alcohol could impair conception are unclear but may include an alcohol-induced rise in estrogen, which reduces FSH secretion suppressing folliculogenisis and ovulation. It may also have a direct effect on the maturation of the ovum, ovulation, blastocyst development and implantation Gill, ; Eggert et al.

Moderate levels of alcohol consumption seven to eight drinks per week have been associated with reduced fertility and an increased risk of spontaneous abortion Windham et al. Levels as low as one drink per week have also been associated with reduced conception Hakim et al. The consumption of alcohol has also been shown to have adverse effects on pregnancy outcome and the most vulnerable time for the unborn child is the first few weeks after conception Day et al. Current evidence is inconclusive regarding what dose of alcohol may be safe to consume during pregnancy, making it difficult to predict the risk Mukherjee et al.

A prospective study of healthy women Hakim et al. A diary was also kept of frequency of intercourse, vaginal bleeding and any pregnancy symptoms. Similar results were found in a Danish study of couples attempting their first pregnancy Jensen et al. Alcohol consumption was monitored over six menstrual cycles and records were kept of vaginal bleeding and frequency of intercourse.

The chance of conception decreased with increasing alcohol intake in a dose-related fashion; women consuming one to five drinks per week had a fecundability OR of 0. Alcohol intake for men was not associated with a reduction in fecundability.

A Swedish study followed a cohort of women over 18 years — Eggert et al. Information was collected on rates of attendance to hospital for various reasons including infertility examinations.

During this period, almost all infertility examinations in Sweden were treated in hospitals. A questionnaire at the beginning of the study was used to assess alcohol intake and medical records were reviewed for admissions for infertility. The effect of high or low alcohol use was compared with moderate use. Therefore, this study demonstrated a dose—response relationship between level of alcohol consumption and fertility examinations.

Limitations of the study include the single point collection of data on alcohol consumption prior to the start of the study and no analysis of smoking and lifestyle. Only weak support was provided by a study of randomly selected women and pregnant or recently delivered women from a range of different European countries Olsen et al. Data were collected on alcohol consumption and other lifestyle factors such as smoking, age and frequency of intercourse prior to conception.

Only at the highest levels of alcohol consumption was an association found between alcohol consumption and decreased fecundity. Other studies have found no effect of alcohol consumption on fertility or the risk of spontaneous abortion Parazzini et al. Both male and female alcohol consumption affected some measures of reproductive performance.

A higher risk of miscarriage was associated with female alcohol consumption 1 week prior to the procedure after adjusting for variables including smoking and age—RR 2. Male alcohol consumption was also significant. In contrast, a study Zaadstra et al. Although adverse effects of any level of alcohol consumption on reproductive performance is highly plausible, studies generally have relied on women or couples recalling their levels and timing of alcohol consumption.

Clearly, the randomized controlled trial to quantify the effect of alcohol consumption on fertility cannot be done. The summation of evidence of associations between psychological stress, caffeine, alcohol consumption and reproductive performance is inconclusive.

Although better evidence is required, it is biologically plausible that these factors may affect reproductive performance. It is therefore prudent to adopt recommendations that address these factors.

Increased psychological stress has been implicated in impaired fertility and the efficacy of ART treatment. Therefore, couples should be assisted to minimize and cope with psychological stress when attempting pregnancy. Some reports regarding the effect of alcohol and caffeine consumption on fertility are conflicting and there is potential for error in the recall of consumption of exact dosage and residual confounding.

The potential for environmental and occupational exposures to chemicals and pollutants to adversely affect fertility is not surprising, as environmental and lifestyle factors are said to be key factors in human disease Czene et al. Certain environmental exposures have been implicated in adverse effects on reproduction.

Adverse effects of radiation on male and female reproduction have been demonstrated in various animal species as well as human beings Kumar, The reproductive system in males and females are sensitive to radiation causing temporary or permanent sterility dependent on dose, duration and dose rate Schieve et al. However, there is a lack of evidence to support an association between exposure to electrical and magnetic fields and fetal loss or adverse pregnancy outcomes Shaw, Exposure to pesticides and solvents has been associated with sperm threshold values below normal Oliva et al.

Supporting these findings is a study of couples undergoing IVF in the Netherlands Tielemans et al. A reduced implantation rate was found in women whose partners worked in occupations with high levels of organic solvent exposure. Men exposed to pesticides and welding have been shown to be at risk for oligozoospermia Wong et al. Certain phthalate metabolites are related to reduction in semen quality Duty et al. In females, cosmetics have been associated with an increased risk of spontaneous abortion John et al.

Other studies have not found an association between occupational exposures and infertility Gracia et al. There is evidence of an adverse effect of some pollutants and chemicals on human reproduction and of an association with exposure to other environmental factors. Although further research is needed to clarify and improve the existing knowledge in this area, couples attempting pregnancy should be individually counselled regarding any potentially harmful occupational exposures. The combined effect of several negative lifestyle factors has been associated with a progressive reduction in fertility.

A cohort of pregnant women were surveyed about their lifestyle and the time taken to conceive Hassan and Killick, The effect of increasing numbers of negative lifestyle variables on the cumulative conception rates within 1 year for a pregnant population. The lines represent the cumulative conception rates for subgroups with different numbers of negative lifestyle variables as follows: Republished from Hassan et al.

There is a large body of evidence relating to the impact of lifestyle on reproductive performance. However, motivating patients to modify their lifestyle can be difficult and challenging. Changing lifestyle behaviours requires time, considerable effort and motivation Rollnick and Heather, A patient-centred approach to counselling and advice has been shown to produce the best outcomes Britt et al.

The provision of evidence-based information relating to the impact of lifestyle and reproductive performance can assist in motivating couples to modify their lifestyle. Motivational interviewing has also been used effectively to assist patients in lifestyle changes Britt et al. A pathway designed around individual aetiology and lifestyle would be planned for each couple. The aim being to provide the most effective and appropriate methods towards reaching the goal of improved reproductive performance, pregnancy and ultimately a healthy child.

The pathway would aim to facilitate both immediate and long-term lifestyle changes. Each couple has a common starting point of infertility and a clinical consult incorporating a medical assessment and identification of modifiable lifestyle factors. Comprehensive experimental studies in both humans and animals demonstrate that salt ingestion causes a profound reduction in nitric oxide NO in vascular blood vessels tissues throughout the body, including the penis.

Salt which we get mainly from processed foods and cereals severely reduces NO in blood vessels, including the penis. An erection required for intercourse cannot occur without normal blood concentrations of NO. So any nutritional factor, such as salt, which reduces synthesis and production of NO should be avoided, if your goal is to maintain a fully erect penis during intercourse.

Virtually all contemporary processed foods have high salt contents 14 — another good reason to adopt The Paleo Diet. A caveat to this concept are foods which increase NO production and promote normal erectile function. These are the foods which you should focus upon.

Omega 3 fatty acids stimulate NO release. Additionally antioxidants such as zinc in the form of glutathione boost NO production while preventing its breakdown. As I have indicated time and again, The Paleo Diet is not a diet at all, but rather a lifelong program to maximize health and well being by consuming, natural living foods and avoiding processed foods.

All body tissues be they male or female , including our reproductive organs respond positively when they are provided an environment and milieu consistent with that which shaped our species over millions of years of evolutionary wisdom.

Male reproductive function including ED can improve by eliminating the ubiquitous processed foods in the standard American Diet. You can go a long way in improving your erection and sperm quantity and quality by eliminating refined sugars, high glycemic load carbohydrates, dairy products and salted foods.

With contemporary Paleo Diets, I advise you to avoid processed meats like bacon, sausages, bologna, salami, prosciutto, liverwurst, hot dogs, ham, and the like. All of these meats are incredibly high in salt and typically maintain a fatty acid profile that looks nothing like fresh, unadulterated wild or grass produced meats 59, 60 — to say nothing of the preservatives and additives which are part of these meats. A recent study indicates consumption of processed meats in healthy young men is associated with a lower sperm count.

These fats may increase shelf life of processed foods, yet have been known for more than two decades to have adverse effects upon human health. If you voluntarily decide to eliminate or reduce animal foods from your diet via vegetarian or vegan protocols, you will almost certainly become deficient in vitamin B As I have previously pointed out, B12 deficiencies universally result in elevated homocysteine concentrations throughout the body, including the testicles and ovaries which impair fertility for both men and women.

Infertility and ED are diseases which have increasingly been associated with the same dietary and environmental factors that elicit the chronic diseases of civilization obesity, overweight, cardiovascular disease, type 2 diabetes, hypertension, acne , gout and a number of cancers. The same protective dietary measures The Paleo Diet that reduce or eliminate symptoms of the diseases of civilization almost certainly will promote positive reproductive function in men of all ages.

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Dissociation of the glycaemic and insulinaemic responses to whole and skimmed milk. Br J Nutr ; High intakes of milk, but not meat, increase s-insulin and insulin resistance in 8-year-old boys. Eur J Clin Nutr. Studies on the bioavailability of zinc in humans. Interaction of beef-zinc with iron, calcium and lactose. Calcium and iron absorption: Role of zinc trafficking in male fertility: Zinc levels in seminal plasma are associated with sperm quality in fertile and infertile men.

Impact of seminal trace element and glutathione levels on semen quality of Tunisian infertile men. World Review of Nutrition and Dietetics, The trouble with beans.

Hominoid evolution and the influences on sodium homeostasis. The Hunger for Salt. Springer-Verlag, New York, , pp. The effect of high salt intake on endothelial function: Pathophysiological role of the renin-angiotensin system on erectile dysfunction. Eur J Clin Invest. Evidence that the vasodilator angiotensin- -Mas axis plays an important role in erectile function. An oral formulation of angiotensin- reverses corpus cavernosum damages induced by hypercholesterolemia.

A multifaceted approach to maximize erectile function and vascular health.

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