Antioxidants, Oxidative Stress and your Fertility – part Two

In Part One of this article, we’ve explained what ROS are and what role antioxidants play when it comes to male fertility. There is still much speculation about exactly which tablets (or combination of tablets) are best to take to most effectively improve sperm quality. Here we will go through some of the options available for men who want to try and boost the quality of their sperm with antioxidant supplements.


Carnitine is a molecule that carries fat (an energy source) around cells so that they can burn the fat to get the energy they need to function. Sperm cells need a lot of energy because their journey to the egg is so long and difficult. And sperm that don’t have this energy aren’t going to be very good swimmers and they aren’t going to stand a chance at fertilising an egg. As an added bonus, carnitine is also an antioxidant – it ‘scavenges’ ROS to stop them causing any damage in cells.

Research has shown that taking antioxidant supplements in the form of L-carnitine and/or acetyl-L-carnitine can help to improve a man’s sperm quality. In one study, men with a low sperm quality took 2 grams (g) of L-carnitine and 1g of acetyl-L-carnitine a day for 6 months. Compared to men with a similarly low sperm quality who had not been taking the antioxidants, the men who had been taking carnitine had improved sperm concentration, movement and physical characteristics after taking the supplements. And whereas men who weren’t taking the tablets only experienced a partner pregnancy rate of 1.7%, men who had been taking the supplements ended up conceiving with their partner at a rate of 21.8%.

Vitamin C

Vitamin C also has antioxidant capabilities and has been shown to help improve the sperm quality of men with damaged sperm. One research study looked at the effect that vitamin C supplements had on 120 Indian men who had a low sperm quality because of exposure to lead at work. The researchers gave the men 1g of vitamin C for five days a week for three months. After this treatment, the researchers found that sperm movement and total sperm count had increased and the number of sperm with abnormal characteristics had dropped.

Coenzyme Q10 (CoQ10)

CoQ10 is an antioxidant which also plays an important role in helping sperm cells get energy. CoQ10 supplements are known to improve sperm quality. A team of researchers carried out a study with 212 infertile men. Half of the men were given 300 milligrams (mg) of CoQ10 in a tablet once a day for 26 weeks and the other half of the men were given a placebo treatment (they were still given a daily tablet but it did not contain any active ingredient). After the treatment, the men who had been given the CoQ10 supplement had an improved number of sperm, improved sperm movement and an increase in the number of sperm with normal physical characteristics. And the longer the men were given the supplements, the higher these increases were.

Another study also showed that CoQ10 can help boost pregnancy rates. The researchers gave daily doses of 60mg of CoQ10 to 17 patients who had experienced low fertilization rates after intracytoplasmic sperm injection (ICSI), which is a type of in-vitro fertilisation (IVF). These patients took the supplements for 103 days, on average, before their next ICSI treatment. Remarkably, pregnancy rates went from around 10.3% in their previous ICSI cycles to around 26.3% after the CoQ10 treatment!

Fish for lunch
Photo credit: Migle Seikyte / Foter / CC BY-SA

Omega-3 fatty acids

These molecules are a type of fat and they are found in either fish or plants. Although they’re not considered to be one of the most beneficial antioxidants, they certainly help to reduce the levels of ROS and therefore have antioxidant qualities. Omega-3 fatty acids also help sperm cells to bind to egg cells so that a living embryo can be produced.

One study involving 238 infertile men was carried out to examine the effect of omega-3 fatty acid supplements. Half of the patients were given omega-3 fatty acids in the form of 1.84g of EPA and DHA in a tablet each day for eight months. The other half of men were given a placebo treatment for the same amount of time. In the men who had taken the omega-3 fatty acid tablets, the researchers found that total sperm count and sperm cell concentration was improved. What’s more, another study found that couples undergoing IVF or ICSI treatments could increase their probability of pregnancy by sticking to a Mediterranean style diet – which includes many foods rich in omega-3 fatty acids.

Vitamin E

Vitamin E also helps sperm bind to eggs and helps stop ROS from damaging sperm DNA. According to one study, men who take vitamin E in a supplement form of 1g a day for three months (in combination with a 1g supplement of vitamin C for the same time) can improve the quality of their sperm DNA. In a different research study, 38 men with a low quality of sperm DNA who had undergone one failed treatment of ICSI were given 1g of vitamin C and 1g of vitamin E for two months. The researchers found that in 76% of cases, the treatment led to a decrease in the amount of damaged sperm DNA. When another ICSI treatment was performed, there was a marked improvement in the men’s partners’ pregnancy rates.

N-acetylcysteine (NAC)

NAC is a type of amino acid – which are natural and essential molecules produced in the body. The molecule acts as a direct antioxidant and it also improves existing antioxidant systems in cells. NAC can also help to reduce the viscosity of ejaculated semen, which is a bonus, as it makes it easier for sperm to reach an egg. NAC can also prevent sperm from being damaged by toxic chemicals. Some research shows that infertile men can benefit from improved sperm volume, movement and viscosity by taking 600mg of NAC in a supplement each day for three months. Further studies also show that taking 600mg of NAC a day for 26 weeks (both by itself and with selenium supplements) can help men to raise their testosterone levels.


Zinc is one of the most potent antioxidants and so has a high potential to improve sperm quality. Men with low amounts of zinc tend to have poor quality sperm because of high oxidative stress and also a lower overall volume of sperm.

One study gave infertile men 66mg of zinc sulphate and 5mg of folic acid in a tablet form each day for 26 weeks. After the treatment, the men experienced a 74% increase in total sperm count. A different research study also found that giving infertile men 250mg of zinc twice daily for three months led to an improvement in sperm count, sperm movement and sperm fertilising capacity. The treatment also led to decrease in sperm DNA damage and the number of physically abnormal sperm.

Vitamin D

Vitamin D has antioxidant abilities – but its effect has not yet been directly tested in infertile men. However, it is known that there is a receptor for vitamin D present in all types of tissue in the male reproductive system and low vitamin D levels are associated with poor sperm quality. It has also been found that many young men are deficient in vitamin D. One study found that adding vitamin D to human sperm cells in the lab prompts the development of the ‘acrosome reaction’ – which enables sperm cells to bind to eggs. Adding vitamin D also improved sperm movement. So despite the lack of direct human studies, it is likely that vitamin D has beneficial impacts on sperm quality and so infertile men should consider taking supplements of this antioxidant.


Selenium is an antioxidant which is essential for normal testicle and sperm development and sperm function. One study involving 690 infertile men found that taking supplements of 0.2mg of selenium in combination with vitamin E for at least 100 days led to improved sperm movement or physical characteristics or both of these factors in 52.6% of patients. Also, there was a 10.8% improvement in patients naturally conceiving with their partners after treatment.


This molecule is derived from plants and it is a known, powerful antioxidant. Low levels of lycopene are often found in men suffering with fertility issues. In one study, 30 infertile men were given 2mg of lycopene twice a day for three months. There were huge improvements in sperm quality, with 66% of patients showing an improvement in sperm concentration, 53% showing improved sperm movement and 46% of patients showing an improvement in the physical characteristics of their sperm. The researchers also found that 23% of their patients managed to conceive with their partners after treatment.


Extracts from the Ashwagandha plant have been shown to have antioxidant benefits. Stress is one of the major causes of oxidation and other harmful, sperm-damaging effects in the testes. Ashwagandha is used in traditional medicine practices to treat stress and one study shows these beneficial effects extend to helping improve oxidative stress in the testes. In the study, 60 infertile men were given 5g of Ashwagandha a day for three months. This treatment led to an overall decrease in oxidative stress, increased levels of antioxidants and an improvement in sperm quality. After the treatment, 14% of the men treated successfully conceived with their partners.

Antioxidants and assisted reproduction treatments

Photo credit: snre / Foter / CC BY

It’s estimated that up to 15% of couples now face fertility issues and they are increasingly turning to assisted reproduction treatments to help them try and conceive. As with natural conception, sperm quality plays a big role in determining the likelihood of conception in these treatments. So sperm need to be in top condition if they are going to work. This means it’s just as important we think about ROS in relation to treatments where fertilisation is carried out in a lab.

Sperm used for assisted reproduction treatments such IVF are separated from the seminal fluid in which they’re usually held in inside the body. When they leave this fluid behind, they’re losing out on the protective effect that the natural antioxidants in the fluid provide. What’s worse, some of the processes that are carried out during the handling and preparation of sperm for assisted reproduction techniques (such as freezing and thawing of sperm) can lead to the production of ROS. Without the protective effect of antioxidants, sperm collected for assisted reproduction treatments can easily become damaged.

But a study published last month shows how this can be avoided.

The researchers looked at how adding an antioxidant (in the form of zinc) to sperm during treatments such as IVF affected sperm quality. Sperm were collected from 20 healthy men and then mixed with either just a ROS, just zinc, or a ROS and zinc. Some sperm samples were also mixed with a neutral liquid to check that it was not anything else besides the ROS and antioxidants affecting the sperm. This is known as a control treatment.

The researchers then looked at their samples to check what effect each mixture had produced in the sperm. As expected, mixing sperm with just a ROS led to lower quality sperm than the control group. But when sperm were mixed with a ROS and zinc (the antioxidant), the researchers found that all the sperm characteristics they looked at were improved in comparison to the sperm that had been mixed with just a ROS.

So it appears the increasing number of couples turning to assisted reproduction treatments for help conceiving can also benefit from the beneficial and protective effects of antioxidants.


There are a lot of options available for men hoping to improve their sperm quality and overall fertility by increasing their antioxidant intake. There is a distinct lack of treatments available for men with poor sperm quality. And – as antioxidant supplements and antioxidant rich diets don’t have any negative side effects – men wishing to improve their sperm quality should definitely consider increasing their intake of antioxidants in one way or another. Every little helps when it can seem like the whole world is against a sperm on his mammoth journey to find and fertilise an egg. And often the beneficial effect of antioxidants on sperm quality and pregnancy rate is huge.

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