Topic of the Month

Micronutrients and men’s sexual health

January 1, 2012

Sexual health is of particular importance to a man: not only when he wants to start a family, but during all phases of his life. And while sexuality’s functions differ from man to man, in almost all societies there is a connection between a man’s success and his sexual health. This applies to most aspects of a man’s life as his body’s functionality and performance must be just as good sexually as it is in his working life and in sports. Hence, sexual health affects a man’s quality of life and his self-esteem. A balanced, micronutrient-rich diet plays an important part in maintaining sexual and reproductive health.

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In the phase of life between ages 20 and 50, reproductive health is generally the main concern because it corresponds directly to the possibility of fatherhood i.e. starting a family. A man’s awareness of his body’s vulnerability grows as he experiences his first problems, usually starting around age 40. One example of such a problem is realizing that constant stress negatively affects the libido and sexuality. Moreover, between ages 40 and 50, the production of sexual hormones falls by 30 to 80% in comparison to adolescence. Above all, this can impinge on fertility (sperm quality, erectile functions and libido) and prostate health.  

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Reproductive health

Reproductive health includes a satisfactory sex life that does not represent a hazard to health or the ability to reproduce. The male erection is a pre-condition for penetration during sexual intercourse that is intended to lead to reproduction. An erection is brought about by an increased influx of blood through the deep artery of the penis and concomitant blockage of venous drainage via the deep vein of the penis in the corpora cavernosa. Blood pressure in the penis rises to around ten times the arterial blood pressure in the rest of the body. Hence, healthy blood vessels are of crucial importance for proper erectile function. The focus here is on the endothelium, a thin layer of cells that line the inner wall of the blood vessels. Endothelial cells are the main protagonists in the regulation of blood flow, blood pressure and coagulation. There are indications that raised levels of oxidized LDL cholesterol, trigly-cerides and homocysteine in the blood may increase the risk of endothelial dysfunction (1). Consequently, if micronutrients with antioxidant effects are able to maintain a normal vascular tone by reducing vascular oxidative stress, this could be generally important for preventing vascular diseases and, more specifically, for preventing erectile function disorders.

Several studies have described the benefit of antioxidant vitamins C and E for improving general endothelial function in both healthy subjects (2) and in high risk groups (3, 4). Trials have also indicated that these vitamins could prevent endothelial dysfunction caused by raised levels of homocysteine in the blood (5). One recent study furnished evidence that vascular endothelial function could be dependent on vitamin D status: low blood levels of vitamin D were associated with vascular endothelial inflammation (6). Further-more, it has been demonstrated that food supplements with vitamin D can improve vascular endothelial function (7).

Additionally, blood flow is regulated by nitric oxide (NO), which causes blood vessels in the body to expand and thus lowers blood pressure. NO also relaxes the blood vessels in the penis, allowing the corpus caver-nosum to fill with blood in response to sexual arousal. Studies have shown that omega-3 fatty acids can stimulate endothelial release of NO. Moreover, antioxidants can increase NO production and delay NO breakdown. There are also indications that folic acidvitamin Cvitamin E and calcium can support the biochemical processes leading to NO release. Certain food supplements could therefore favorably influence erectile function (8).

Another important feature of reproductive health is male fertility. Healthy and motile sperm is essential for this. Sperm contain a large number of mitochondria that provide energy, but that can also cause oxidative stress in these cells. It is imperative that sperm cells be protected against oxidative damage: it is postulated that 30 to 80% of male subfertility cases are due to the damaging effects of lifestyle-related oxidative stress (9, 10). Supporting the body’s own antioxidant protection through food supplements containing the relevant micronutrients can improve sperm quality in affected men (11, 12). Vitamin E (13) and coenzyme Q10 (14, 15) have been identified as particularly effective antioxidants for the protection of sperm; the former can even protect against the DNA damage that occurs when frozen sperm is thawed (16). Food supplementation with coenzyme Q10 and lycopene was also associated with improved sperm quality (17). Furthermore, there are indications that increasing the intake of selenium, an antioxidant trace element that appears to protect the proteins in the sperm cell membrane against oxidative damage, could increase the quantity and the quality of sperm (18). A sufficient supply of zinc and folate, which is involved in spermatogenesis, also appears to be important (19). Thus researchers found a link between increased DNA damage and a low concentration of folate in semen (20). Moreover, a variation (polymorphism) in the methylentetrahydrofolate reductase (MTHFR) gene, which has a central function in folate metabolism, could be the cause of an increased risk of idiopathic male infertility (21).

Vitamin A plays a key role in spermatogenesis. One study showed that aging men, men with an increasing body mass index and smokers have lower vitamin A and vitamin E concentrations, and that this, in turn, is associated with reduced semen quality (22).

Vitamin D, too, obviously influences male semen cells. The results of one study showed that higher vitamin D levels were associated with better sperm motility and an increase in intercellular calcium concentration (23). Furthermore, there are indications that a lack of vitamin D could be linked to impaired function of the testes which produce sperm and the male sex hormone testosterone (24, 25).

An adequate intake of long-chain omega-3 fatty acids (PUFAs) also seems to be essential for good sperm quality: the membranes of healthy sperm are plentifully supplied with PUFA. Since these fatty acids are very vulnerable to oxidative stress, they need antioxidants to protect them against damage (26). A lower concentration of PUFAs has been observed in the sperm of infertile men.

Further studies are needed to more accurately investigate the influence of micronutrients on male reproduc-tive health. Vitamins A, E, D and folic acid, as well as PUFAs, are generally among the micronutrients that are often difficult to adequately obtain from average dietary habits.

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Prostate health

The prostate lies just below the opening of the bladder and surrounds the urethra like a ring. This gland produces a secretion that makes up the main component of seminal fluid and is chiefly responsible for the transportation of semen cells. On the one hand, prostate health can be impaired by a benign enlargement (benign prostatic hyperplasia, or BPH), typically caused by male sex hormones starting around age 45 but it could also be a malignant enlargement (cancer). While BPH leads to typical problems with urination, prostate cancer does not initially cause any problems. That is why cancer screening and regular health checks are very important. The pathogenesis and causes of prostate cancer have not yet been fully investigated. Prostate health may be affected by hereditary predisposition, male sex hormones and various lifestyle factors, e.g. diet.
 
Alcohol abuse and an above average consumption of fat are thought to be factors that contribute to the development of prostate cancer. Conversely, several nutrients appear to be involved in the maintenance of prostate health. For the prevention of diseases, it is particularly important to protect the cell membranes and DNA of prostatic tissue against damage from oxidative stress. In one study involving prostate cancer patients, higher blood levels of prostate-specific antigen (PSA) – a marker for excessive prostate growth – were measured in patients with exhausted antioxidant reserves (27). Studies provided indications that antioxidant vitamins, especially vitamin E, could protect the cells of the prostate against malignant growths (28). It was demonstrated that low levels of vitamin E and a lack of zinc and selenium are associated with an rise in PSA values and could therefore represent risk factors for the development of prostate cancer (29). Vitamin A plays a key role in the regulation of cell growth and cell differentiation. Results from a case-control study indicate that higher serum concentrations of vitamin A (retinol) are associated with a reduced risk of developing aggressive prostate cancer (30).

Epidemiological studies have shown that ample consumption of foods containing tomato or soy may be linked to a reduced risk for prostate cancer. Supplementation with lycopene, which is apparently involved in various metabolic pathways connected with the development of prostate cancer, caused blood levels of PSA to fall (31, 32).

A sufficient supply of B-complex vitamins could also have a positive effect on prostate health. B-complex vitamins fulfill important tasks in metabolic processes that provide the crucial precursors for DNA methy-lation, DNA repair mechanisms and nucleotide synthesis, and hence are the guarantee of proper cell division (33). It was possible to show that a high intake of vitamin B6 might improve survival rates for prostate cancer patients diagnosed with a localized tumor that had not yet metastasized (34). Another trial provided indications that a high intake of folic acid could be associated with a reduced risk of developing prostate cancer (35).

Additionally, research is delivering more and more insights indicating vitamin D’s significant role in prostate health. Prostate cells contain vitamin D receptors (VDR) and enzymes important for vitamin D metabolism. In-vitro and in-vivo experiments were able to demonstrate that vitamin D may influence various metabolic pathways in prostate cells and may thus influence their division (36). Consequently, vitamin D could represent an effective therapeutic approach for prostate cancer (37). Large-scale observational studies have established that a high blood level of vitamin D could be associated with a positive prognosis for the non-fatal progression of prostate cancer (38). An overview showed that prostate cancer patients often suffer from vitamin D deficiency (39). Other studies linked high VDR expression in prostate tumors with a reduced risk for mortality (40). Experts have calculated that raising serum 25(OH) D levels from 40 to 60 nanograms per milliliter could cut the mortality rate for prostate cancer in half (41). However, the amount of available data concerning the influence of micronutrients on prostate and other types of cancer is still insufficient and requires more studies for further clarification.

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