Effect of Diet on Sperm

• Introduction to nutrition and sperm
• Obesity
• Metabolic imbalances, metabolic syndrome and non-insulin dependent (type 2) diabetes mellitus
  • Non-insulin dependent diabetes mellitus
  • Dyslipidemia
  • Hypertension
• Dietary nutrients

 

• Nutritional and dietary measures to protect sperm
  • Maintaining a healthy weight
  • Eating a healthy, well balanced diet

 

Introduction to nutrition and sperm

A healthy male produces millions of sperm each day although only a few of these sperm will ever go on to fertilise a human egg and create an embryo. Despite the vast quantity of sperm produced by a healthy man, the number of sperm which actually fulfil their fertilising potential is therefore extremely small. Even when a man is producing sperm at a healthy capacity and his partner is fertile, it is not uncommon for couples to take up to a year to conceive.

Some men produce sperm which is sub-optimal, either in quantity or quality. These men will typically take longer to conceive and are more likely to require the assistance of artificial reproduction techniques to do so. While some men may experience sub-optimal sperm production because of a genetic or birth trait, for example deletions on the Y chromosome or history of cryptorchidism, in many cases sperm production declines over time as a result of exposure to a range of risk factors.

The types and quantity of food a man eats affects his sperm production. Unhealthy eating patterns, including excessive total calorie intake and excessive fat and sugar intake, are associated with sub-optimal sperm production and/or infertility in men.

Obesity

Fertility gradually declines as weight increases above normal levels (i.e. Body Mass Index (BMI) >25kg/m² ). BMI increases if an individual consumes more energy than they expend each day (in terms of total calorie intake), and is particularly likely to increase when individuals consume large amounts of fat and sugar. Thus obesity related infertility is primarily related to poor dietary habits. While further research is needed to examine the exact ways in which obesity impairs fertility in men, there is considerable evidence that the association exists, and that the more a man’s weight increases, the more his sperm production and fertility declines.

Evidence shows that obese men have lower concentrations of testosterone and sex-hormone binding globulin, both important hormones in the sperm production cycle. Studies have also demonstrated that obesity negatively affects semen quality. For example, one study showed that overweight (BMI >25kg/m²) and obese (BMI >30kg/m²) men had significantly lower concentrations of morphologically normal and motile sperm than normal weight (BMI <25kg/m²) men. It also found that men with a BMI >25kg/m² had significantly higher concentrations of sperm with chromatin defragmentation (i.e. abnormalities in the genetic information contained in chromosomes). Another study found that poor semen quality was associated with sedentary occupation and that semen quality worsened as BMI increased.

Several ways that obesity might impair fertility in men have been identified. Obesity in men is associated with a changed hormonal environment characterised by elevated oestrogen and reduced testosterone levels. As sperm production is highly dependent on testosterone, low levels of this hormone are likely to impair sperm production.

Obesity is also associated with increased oxidative stress in the testicles. Oxidative stress is stress induced by increased numbers of molecules containing free oxygen. These molecules are highly reactive and can easily catalyse chemical reactions with other, usually stable molecules. While oxidative stress does not impair sperm production, reactions catalysed by free radical molecules (i.e. those containing unstable oxygen species) can damage healthy sperm following production.

Excessive fat in the thigh and pubic region resulting from obesity, may have an insulating effect on the testicles. This causes the temperature of the scrotum and testicles to increase. Increased scrotal temperature is also thought to negatively influence sperm production.

Metabolic imbalances, metabolic syndrome and non-insulin dependent (type 2) diabetes mellitus

A number of studies have revealed associations between individual metabolic disturbances and various indicators of reduced male fertility and/or poor semen parameters. Metabolic syndrome (a pre-diabetes condition characterised by several metabolic abnormalities occurring simultaneously) and/or type 2 diabetes mellitus are also associated with impaired fertility in men. These metabolic conditions are all associated with poor dietary habits. Obesity also typically occurs with metabolic syndrome and type 2 diabetes (see above for effect of obesity on sperm).

Non-insulin dependent diabetes mellitus

Non-insulin dependent (type 2) diabetes mellitus, is a condition typically induced by poor dietary habits. It is associated with hypogonadism, a rare but important cause of male infertility characterised by an imbalanced hormonal environment and breakdown in the pathway which transmits signals between the brain’s hypothalamus and the man’s reproductive system. While hypogonadism typically comes after type 2 diabetes (and therefore cannot be caused by it), scientists believe that both conditions may be caused by insulin resistance. Insulin resistance results from type 2 diabetes and is one of the metabolic imbalances which characterises metabolic syndrome.

Dyslipidaemia

Dyslipidaemia (increased concentrations of lipids, including cholestrerol in the blood) is another metabolic imbalance characteristic of metabolic syndrome. Evidence of the associations between dyslipidemia and male fertility to date suggests that high cholesterol is associated subfertility in men. One study reported a very high prevalence of dyslipidaemia (65%) amongst infertile men. In addition, a laboratory study in which rats were fed either a high or anti-cholesterol diet showed a reduction in the fertilising capacity of male rats following the high cholesterol diet.

Hypertension

Available evidence suggests that high blood pressure (hypertension) is associated with reduced testosterone, which is likely to affect sperm production.

 

Dietary nutrients

It has been hypothesised that increased intake of antioxidant nutrients may increase male fertility. This is because sperm quality is negatively affected by increasing concentrations of reactive oxygen species in the semen, and antioxidants reduce the concentrations of these molecules.

The results of one laboratory study in which rats were fed anti-oxidant supplements, support this hypothesis. Rats receiving the antioxidant supplements were more likely to mate and experienced increased testicular size and concentrations of morphologically normal sperm, compared to those which did not received antioxidant supplements. However, there remains insufficient evidence of the effect of antioxidants on the fertility of human males, to recommend antioxidant supplementation as a therapeutic intervention.

Nutritional and dietary measures to protect sperm

There are many measures related to diet, alcohol and other drugs which an individual can undertake to protect the health of their sperm. Essentially men need to maintain a healthy weight and eat a healthy, balanced diet.

Maintaining a healthy weight

Maintaining a healthy weight (i.e. BMI between 20-25kg/m²) is an important step in ensuring optimal sperm production, as obesity is associated with reduced sperm production. To maintain a healthy weight, men should ensure that their total calorie intake matches energy expenditure by:

• Reducing total calorie intake: for example by limiting fat and sugar, reducing fast food consumption, eating freshly prepared meals and snacking on fruit or nuts instead of chips and biscuits. Individuals may find it helpful to monitor their calorie intake using a calorie counter;
• Increase daily exercise: to at least 30 minutes per day, for example by integrating exercise into day to day activities like walking to work or bike riding with children;

Eat a healthy well balanced diet

A well balanced diet is one: which is high in fibre, fruits and vegetables and low in fats and sugars. Studies have shown that diet composition affects the metabolism independently of total calorie intake. Eating a range of healthy foods has a protective effect in relation to metabolic syndrome, even amongst obese individuals.

For more tips on losing or maintaining weight, see weight loss.

More information

For more information on nutrition, including information on types and composition of food, nutrition and people, conditions related to nutrition, and diets and recipes, as well as some useful videos and tools, see Nutrition.

For more information on sperm health and male fertility, see Sperm Health

References

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2. McLachlan, R.I. de Krester, D.M. Male Infertility: The Case for Continued Research. MJA, 2001;174:116-7.
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4. Osuna, J.A. Gomex-Perez, R. Arata-Bellabarba, G. Villaroel, V. Relationship between BMI, total testosterone, sex-hormone binding globulin, leptin, insulin and insulin resistance in obese men. Arch Androl, 2005;52(5):355-61.
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