Do all types of sugar affect fertility equally? Are artificial sweeteners a sperm-safe alternative? And what about natural sugars like those found in fruits and vegetables? We’ll explore what the research says about added sugars and male fertility.
What the research says about added sugars and male fertility
Decreased sperm quality accounts for around 25% of infertility cases across the globe, and dietary patterns may play a big role. From sperm motility to testicular function, many aspects of male fertility may be impacted by the consumption of excess sugars. Here is what the research says:
Sugar and semen parameters
Sperm quality depends on a number of factors, including volume, sperm count, motility (the forward movement of sperm), and morphology (the shape of sperm). In a comprehensive systematic review of over 1,944 articles and observational studies, researchers found a correlation between diets rich in sugar-sweetened beverages and impaired motility. Poor sperm motility means that sperm aren’t swimming or are swimming improperly, which can impede their ability to successfully reach and fertilize an egg.
Another 2014 study added evidence for this correlation between sugar intake and lower motility, while noting that other parameters, such as reproductive hormone levels, remained unaffected. Researchers found that sugar-sweetened beverages had the ability to increase insulin resistance, which then increased oxidative stress, negatively influencing sperm motility. In addition, conditions characterized by insulin resistance, such as type 2 diabetes, have also been related to lower sperm motility.
Sugar intake also correlates with excess weight, which is associated with lower semen parameters such as low sperm count. While the association between obesity and sperm parameters remains a controversial topic, studies show that excess weight and obesity were associated with an increased prevalence of abnormally low sperm count. Their data shows that high BMI affects sperm production, though it remains unclear whether weight loss can reverse this effect.
Sugar and testicular function
The primary function of the testes to produce and store sperm and semen. They’re also vital for creating testosterone and other male hormones called androgens. When testicular function is compromised, so is the quality and volume of semen.
In one recent Danish study, researchers compared the diets of 2,935 men who were unaware of their fertility status. They found that those participants who adhered to a Western diet — high in total calories, meat, cheese, added fats and sugars — had lower sperm counts than those who followed generally healthy or vegetarian diets. Using ultrasonography, researchers found a direct negative effect on the testicles, causing smaller testicular volume.
What about artificial or alternative sweeteners?
Artificial sweeteners have become increasingly popular as an alternative to sugar, classified by the FDA as GRAS (generally recognized as safe). There is significantly less research on the effect of artificial or alternative sweeteners on male fertility. However, animal studies suggest that they may not be safer for male fertility than actual sugar.
Aspartame and male fertility
An artificial sweetener sold under popular brand names such as NutraSweet and Equal, aspartame has been in use in the U.S. since the early 1980s as a way to lower one's intake of added sugars. Though it is the most commonly consumed artificial sweetener, there is evidence from animal studies that aspartame can have a negative impact on many different facets of male fertility.
In one study of 36 adult male mice, those given aspartame experienced notable changes in their sperm quality, including lower sperm parameters, reduced testosterone levels, and even decreased testicular tissue. The rats given the highest dose of aspartame had lower sperm motility and a lower sperm survival rate. Higher doses of aspartame also correlated with abnormally shaped sperm and sperm DNA fragmentation. Interestingly, though aspartame is often sold as a weight-loss product, researchers in this study found that high doses were linked with weight gain.
Stevia and male fertility
A natural sweetener native to South America, stevia is a widely used product that has almost zero calories. That’s because stevia is about 250 times sweeter than sugar, so you need only a tiny amount to attain the same sweetening power. Stevia is often used by those looking to lose weight or prevent their blood sugar from spiking.
One study showed that when male rats were given stevia over a course of 60 days, they did experience weight loss — specifically in their testes. Stevia was also associated with decreased sperm count and lowered testosterone levels, presenting a possible correlation between the alternative sweetener and impaired male fertility.
Sucralose and male fertility
The most common sucralose product is Splenda, marketed as a no-calorie sweetener that’s “made from real sugar” — using a chemical process that tweaks its structure.
When it comes to the effects of sucralose on male fertility, thus far, researchers have found no connection between the artificial sweetener and impaired fertility. One animal study showed that sucralose corresponded with lower food consumption and reduced weight gain in rats, and their sperm production remained uncompromised.
What about natural sugars from fruits and vegetables?
Sugar is present in almost all fruits and vegetables, where it’s found in the form of glucose and fructose. But the natural sugars in fruits and vegetables are not typically a health concern, because they come alongside fiber and crucial vitamins. In fact, fruits and vegetables are some of the most important superfoods for male fertility.
As shown in the Danish study that compared Western diets with generally healthy or vegetarian-like diets, a higher intake of fruits and vegetables is associated with improved semen parameters. Another study of men who had sperm analyzed at a fertility clinic showed that those who ate higher amounts of fruits and vegetables as part of a Mediterranean diet had higher sperm concentrations and better sperm motility compared to men who ate less of these foods.
This is thought to be because plant-based whole foods are high in vitamins like folate and antioxidants such as vitamin C, selenium, and lycopene, micronutrients that have all been linked to higher sperm concentrations in systematic studies. Learn more about male fertility supplements.