The reproductive timeline

The age of a man or woman is a factor among others that can affect fertility. Many couples choose to delay child-bearing due to the pursuit of education and other factors. Fertility peaks and then decreases over time in both men and women, thus the reproductive timeline may be one aspect to consider when determining the ideal time to start a family. As men age, levels of testosterone begin to decline, resulting in hypogonadism. However, if testosterone is used to treat hypogonadism, it may suppress spermatogenesis. After the age of 40, men may experience significantly more DNA damage in their sperm, as well as decrease in both motility (40%) and viability (less than 50%).

Women’s reproductive timeline is complex. A woman is born with all the oocytes she will ever have, and only 400–500 are actually ovulated. As the number of oocytes decreases, the menstrual cycle of a woman shortens, infertility increases, and menstrual irregularity begins 6–7 years before menopause. Increasing age increases the time of pregnancy for a woman. When a woman is under the age of 30, her chances of conceiving can be as high as 71 percent; when she is over 36, it may only be 41%. The chances of becoming pregnant and being able to keep pregnant are also affected. 

Impacts of diet and exercise

Nutrition

Eating a healthy and varied diet can be an important part of maintaining good overall health. However, some vitamins and food groups may have a greater impact on reproductive health than others. Aspects of a male’s diet may have an impact on its fertility. Consuming a diet rich in carbohydrates, fiber, folate, and lycopene as well as consuming fruit and vegetables correlates with improved semen quality. Lower protein and fat consumption was more beneficial for fertility. Another potential benefit could be antioxidants, which by scavenging reactive oxygen species (ROS) play a pivotal role in the body. A collection of free radicals and non-radical oxygen derivatives are reactive oxygen species or ROS.

Ultimately, a woman’s diet can affect her fertility, especially ovulation. Overall, it has been shown that the substitution of carbohydrates with animal protein is detrimental to ovulatory fertility. Including only one serving of meat was associated with a 32% higher risk of developing ovulatory infertility, particularly if the meat was chicken or turkey. However, a beneficial effect was demonstrated by replacing carbohydrates with vegetable protein. Choosing trans fats in the diet instead of monounsaturated fats has been demonstrated to drastically increase the risk of ovulatory infertility. Consuming trans fats instead of carbohydrates correlated with a 73 percent increase in risk of ovulatory disorder. The use of multivitamins and supplements also has an effect. Women taking multivitamins may experience less ovulatory infertility; women taking six or more tablets had the lowest relative infertility risk followed by women taking three to five and two or less. Women with high “fertility diet” ratings demonstrated by a higher trans-fat monounsaturated ratio, vegetable over animal protein, high-fat over low-fat meat, lower glycemic load, and improved iron and multivitamin intake had lower infertility levels due to ovulation disorders.

Eating disorders and being underweight

Obesity is not the only way that weight can affect fertility. There is also a risk of infertility for men who are underweight. Men who are underweight tend to have lower concentrations of sperm compared to those with normal BMI.

For women, ovarian dysfunction and infertility are associated with being underweight and having extremely low amounts of body fat. Moreover, for women with a BMI below 17.A meta-analysis of 78 studies, which included 1,025,794 participants, the likelihood of ovulatory infertility rises showed that underweight women had an increased risk of preterm birth. Although relatively rare, eating disorders may have a negative effect on menstruation, fertility, and maternal and fetal well-being. It was found that among infertile women suffering from amenorrhea or oligo menorrhea due to eating disorders, 58% had menstrual irregularities. It was found that infertile women seeking intrauterine insemination (IUI) were diagnosed with an eating disorder, suggesting that women with eating disorders history may have a higher risk of infertility.

Psychological effects

Stress, whether physical, social or psychological, is a prominent part of any society. “Men who feel stressed are more likely to have lower sperm concentrations in their ejaculate, and the sperm they have are more likely to be misshapen or have impaired motility,” Stress and depression are thought to reduce testosterone and luteinizing hormone (LH) pulsing, disrupt gonadal function, and ultimately reduce spermatogenesis and sperm parameters. It is not fully understood how stress affects semen quality. It may trigger the release of glucocorticoids called steroid hormones, which may blunt testosterone and sperm production levels in turn. Oxidative stress, which has been shown to have an effect on semen quality and fertility, is another possibility. Whether depression causes low testosterone, or low testosterone can cause depression, it has yet to be determined.

A recent study found that women with high levels of alpha-amylase, a stress-related enzyme, have a harder time getting pregnant. Samples of saliva from 274 women over six menstrual cycles showed that those with the highest concentrations of enzymes during the first cycle were 12% less likely to conceive than those with the lowest concentrations. Alpha-amylase, long known as an enzyme that helps the body digest starch, has only recently been recognized as an indicator of stress, and alpha-amylase is secreted when the nervous system produces compounds known as catecholamine in response to the stress reactions of “fight or flight.” There is early evidence that catecholamine released in response to this type of stress reduce blood flow, delaying the passage of the fertilized egg to the uterus.

Conclusions

Factors of lifestyle, including age when starting a family, nutrition, weight management, exercise, psychological stress, cigarette smoking, use of recreational and prescription drugs, consumption of alcohol and caffeine, environmental and occupational exposure, preventive care and other behaviours are modifiable and can affect fertility.

The evidence suggests that age can play a significant role in determining fertility. Attempting pregnancy for women before the age of 30 and for men before the age of 35 can offer the highest chance of success. Although considering their age is important for one partner, it is when both partners consider together their ages that they may be able to increase their chances of successful pregnancy thoroughly. Adequate nutrition, weight, and exercise can affect fertility. Although no definitive link has been drawn, it may be vital to choose proper nutrition, whether it is to choose supplements or food groups, to improve fertility for both men and women before and during attempts to conceive. To minimize complications and improve fertility outcomes, it is important to understand how lifestyle habits can help or hurt fertility. Through understanding the impact of lifestyle on reproductive health and consciously changing behaviours in the lifestyle, men and women are able to control their own capacity for fertility.