Potential effects of different factors on the reproductive health of men and women. How does lifestyle affect fertility?
"A series of different factors in lifestyle can be altered in order to enhance the overall welfare (...) they play a key role in determining our reproductive health (...)".
Author: Noemi Díaz Arróniz
Infertility is considered a clinical condition, defined (by consensus) by the failure to achieve natural pregnancy after one year of unprotected sexual intercourse (1). It implies serious psychological consequences, and so it results in a stressful experience for infertile couples (2). The prevalence of infertility has increased since 1955, and nowadays it affects at least 15% of couples in reproductive age (1, 2).
A series of different factors in lifestyle can be altered in order to enhance the overall welfare. It is important to remember that these factors are ultimately under our own control, because they play a key role in determining our reproductive health and they can positively or negatively affect fertility (1). The concept "quality of life" (QOL) refers to the well-being of individuals, and it is affected by both individual and social factors (3).
Here we report the potential effects of different lifestyle factors on the reproductive health of men and women. Even though many aspects of life are not subjected to modification, lifestyle itself may be changed for good (1).
1. TIMELINE OF REPRODUCTION: ADVANCED AGE.
Advanced maternal age is a risk factor for fertility, and it has been reported to be directly related to a variety of problems, such as pregnancy loss, obstetric complications, foetal anomalies and different genetic conditions like Down syndrome.
Due to changes in lifestyle, economic factors, social environment, or the will to grow professionally and acquire a proper education level, numerous couples currently choose to delay their parenthood. This implies that the age to father children becomes slowly (but inevitably) higher (1).
Advanced age negatively influences the clinical pregnancy rate after in vitro fertilization (IVF). In particular, this responds to an increased rate of embryo aneuploidies. Several studies have shown a direct relationship between the risk of foetal loss and the age of women older than 35 (5).
It is of no surprise that the current rhythm and lifestyle generates high levels of anxiety, and alterations of the endocrine system can seriously affect fertility (1). Both folliculogenesis and spermatogenesis (production of eggs in the ovaries and sperm in the testes, respectively) are strictly regulated by several hormones, and so any alteration of the hormone balance may have immediate negative effects on the quality of eggs and/or semen (5). It is also worth remembering that the stress caused by the frustration of not achieving pregnancy can directly affect hormone levels and, consequently, impede conception in first place (1).
Taking care of nutrition habits is essential not only for the overall health, but also for reproductive health (7). A balanced diet can help to improve fertility and reproductive potential for both men and women. The lack of specific elements or nutrients may eventually derive in some degree of infertility (2). As an example, it is always recommended to have a regular intake of food rich in antioxidants, such as fruit, vegetables, fibre, carotenoids.... (1). Besides containing antioxidants and essential nutrients, vitamins and folate are found in fruit and vegetables; these substances are involved in DNA and RNA synthesis, and thus play an important role in spermatogenesis by protecting the sperm DNA from free radical damage (7).
Modifying dietary habits can affect ovarian function, which can be correlated with changes in the concentration of circulating hormones including insulin and leptin. These hormones are tightly associated with the initiation and synchronisation of follicle growth, and it seems that its production is regulated, at least partially, by oestrogen secreted by the developing follicle.
It is also advisable to minimise the intake of saturated fats and cholesterol, to avoid excess that might affect the production and balance of sexual steroid hormones like progesterone. Insulin and leptin, in turn, are also associated with the proper initiation of menses; young girls with the wrong levels of certain hormones may see their menarche delayed or even suppressed.
Maintaining a healthy body weight is also essential for the optimal reproductive potential. A reduced index of body fat may impede the regular ovarian cycle in women. Also, obesity is one of the factors with a high impact on fertility, and one of the main causes of adverse effects on the early development of the embryo, too. Numerous studies have demonstrated a direct relationship between excess body mass and the diminished reproductive capacity (1).
On one hand, obesity increases the probability of suffering from miscarriage due to endocrine and metabolic alterations. It affects the quality of eggs and, subsequently, the embryos formed after fertilization (which may also result in severe developmental problems for the neonates). And on the other hand, an excessively low body mass index (BMI) also reduces the chances of pregnancy due to hormone imbalance and the inability to produce specific sexual hormones, which in turn cause abnormal menstrual cycles and obstetric complications (7).
4. TOBACCO AND ALCOHOL
The ingestion of toxic substances like tobacco, alcohol and other drugs has a potentially harmful effect on both oocytes and sperm. In men, consumption of alcohol has been linked with several negative side effects, such as testicular atrophy, decreased libido and reduced sperm count (1, 2). These symptoms are also typically found on those men who present steroid abuse (like in some cases of bodybuilders) (8). Alcohol use during pregnancy is an established cause of foetal alcohol syndrome (FAS). Several studies have recommended that pregnant women should avoid alcohol during pregnancy. In recent years it has consistently been shown that one drink (or more) per day or more increases the risk of spontaneous abortion, intrauterine growth retardation and low birth weight. An increased alcohol intake intake may reduce birth length and head circumference, cause preterm birth, defects in development and cognitive problems (9).
Nicotine abuse, in turn, may impede sperm motility and affect their overall viability. But high consumption of tobacco may also cause genetic alteration in ovocytes and, therefore, in embryos derived from them (2).
Women seeking to get pregnant are normally limited their coffee intake up to no more than 2-3 cups per day. Again, the abuse of caffeine may result in higher probabilities of suffering from a miscarriage (2, 8).
5. ENVIRONMENTAL FACTORS
Exposure to certain chemical substances like pesticides or simply heavy metals may disturb the hormonal balance and negatively impact fertility. This is particularly evident in men; modern lifestyle features including pollution, large urban areas or industry have left their impact on the capacity of producing sperm within the last decades (2).
For instance, direct and continued exposure to heat sources or radiation have a direct effect on sperm DNA fragmentation and motility, which are some of the main features to be assessed in semen analyses. Not surprisingly, the reduced quality of sperm has been documented in men having close and long exposure to mobile devices like laptops and even ovens or saunas (7).
6. PHYSICAL EXERCISE
The regular practice of sports and moderate intensity exercise is beneficial and helpful when it comes to maintain a healthy weight, but also to reduce the levels of stress and anxiety (6). Men who exercise at least three times a week for one hour have been reported to score higher in almost all sperm parameters, compared to men who participated in a more frequent and intense physical activity (1).
Also, and as it has been previously mentioned, the regular consumption of anabolic steroids is an important cause of male infertility, due to the hampered action of testosterone in the testes (1, 7).
Modern lifestyle has been shown to play an important role in fertility. Attempting pregnancy before the age of 30-35 may provide the highest probabilities of success for women. Considering social, professional and personal reasons, it is then advisable to take into account the current possibilities available for fertility preservation while still possible (1).
Because of the impact of nutrition and physical activity on fertility, controlling and maintaining healthy dietary habits (as well as a healthy weight) may provide a way for couples to increase their chances to conceive (1).
As long as there is no pathological cause for infertility, the solution to some related problems may be as simple as to correct certain wrong habits (8). By understanding the impact of lifestyle on reproductive health and by actively modifying specific behaviour patterns, men and women may be capable of controlling their own fertility potential (1).
http://www.who.int/reproductivehealth/topics/infertility/definitions/en/ (september 5, 2017)
http://www.minifiv.es/2017/02/como-afecta-el-estilo-de-vida-a-la-fertilidad/ (september 20, 2017)