Human reproduction is a complex biological process that occurs from the union of two cells or gametes, the female one, the oocyte or egg cell, and the male one, the spermatozoon (fertilisation). Fertilisation gives birth to the zygote, the cell from which the embryo will be derived, which will develop over the course of pregnancy until delivery. The various steps of reproduction are strongly influenced by lifestyle and, particularly in the area of nutrition, by energy and nutrient intake. Oocytes and spermatozoa must, in fact, develop in a healthy, nutrient-rich environment capable of meeting the metabolic needs of gametes and guaranteeing optimum maturation, quality and competence. The same applies to the intrauterine environment for the proper development of the foetus up to the ‘baby in arms’.
The ability of an individual and/or couple to reproduce is defined as fertility. In contrast, infertility is defined by the World Health Organisation (WHO) as the absence of conception after 12/24 months of regular unprotected targeted sexual intercourse. More than 80-85% of couples conceive within a year. Half of the couples who do not conceive in the first year do so in the second. Approximately 60,000 couples experience reproductive difficulties each year; we speak of male (40%), female (40%) or couple (20%) infertility.
Among the major causes of infertility are
- sexually transmitted disease infections
- gynaecological or andrological pathologies
- socio-economic factors, especially late childbearing
- environmental factors (esposoma)/lifestyle
- unbalanced diet
- suboptimal body weight and body fat mass
- chronic stress
- drug use and alcohol abuse
- poor sleep hygiene
- exposure to environmental contaminants
- immunological factors and alterations in the composition of the microbiota (population of microorganisms)
Diet. Focusing on the link between diet and fertility, it should be specified that the scientific literature loudly reports, especially in recent years, that a healthy lifestyle and correct eating habits show a direct correlation with increased reproductive capacity, both male and female, while an incorrect diet, the main cause of overweight and obesity, significantly impacts fertility, negatively affecting various steps of reproduction, such as the ovulation process in women, but also the molecular composition of the spermatozoon in men. Particular attention must be paid to the quality of food, in order to favour not only the right intake of nutrients, but also the missed/reduced introduction of pollutants (antibiotics, growth hormones, pesticides, mercury, bisphenols, plastics), as substances capable of mimicking hormonal action (endocrine disruptors), to which the spermatozoon is particularly ‘sensitive’.
A healthy diet influences fertility in that it can help establish conditions in the body that maximise the reproductive capacity of the couple seeking pregnancy, the main ones being
- adequate body weight and optimal body composition (fat mass and fat topography)
- regulation of blood glucose/insulin balance
- hormone balance;
- modulation of inflammation.
Maintaining an adequate body weight and especially ideal fat mass percentages is crucial in light of the contribution of (visceral) fat to the body’s inflammatory state (chronic low-grade inflammation). Proinflammatory molecules produced by fat mass interfere with the signalling of insulin, the hormone that regulates the amount of glucose in the blood (blood sugar). Insulin influences, through complex mechanisms, the levels of circulating hormones, both in women (impact on ovulation, for example) and in men. There is, therefore, a very close link between sugar, altered hormone production, inflammation and oxidative stress.
Unbalanced diets, rich in saturated fats, refined sugars and endocrine disruptors, characterised by processed and ultra-processed foods and low in fibre and bioactive compounds (having beneficial properties), promote inflammation, oxidation and cellular ageing, with consequent biochemical effects on reproduction, from the periconceptional phase to pregnancy outcomes.
A balanced diet based on vegetables, low-refined cereals with a low glycaemic index and naturally low in gluten, fruit, pulses, fish and extra virgin olive oil, combined with a moderate intake of dairy products and low consumption of refined sugars and red meat, is the nutritional pattern whose nutritional patterns are opposed to those mentioned above of the Western diet and are able to provide the body with essential bioactive molecules such as, for example, omega-3 fatty acids, vitamin A, B vitamins, zinc, iron, magnesium, selenium, antioxidants (e.g. CoQ10, alpha lipoic acid, vitamin C, vitamin E, resveratrol), vitamin D.
In conclusion, personalised nutrition in the context of infertility can be a valuable support in counteracting inflammation, oxidation and ageing and, thus, improve reproductive health, both in the case of natural pregnancy and in the case of the use of medically assisted procreation techniques (PMA), as a factor that can reduce the time to pregnancy and maximise the response to specific treatments.