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Oxidative stress and Fertility

Oxidative stress is the term for the potential damage that all living cells have to control, simply because sugars, fats and proteins are “burnt” to provide the energy and warmth cells need to function and stay alive.

When things burn, they release chemicals, and we’re pretty familiar with this idea; engines and fires usually give off carbon dioxide and heat. The process is dangerous, which is why it’s best to light fires in safe, specially designed places that can control the process. However, if there are problems with the burning process, the fire can spread or create carbon monoxide and other chemicals that kill people.

The same principles apply when fuel is broken down in our cells in the presence of oxygen to release energy (the oxidation process). Although oxidation in cells is absolutely essential for life, the scientific view is that the damage from by-products (particularly to the DNA and RNA in cells) is the biggest factor in the ageing process.

That burning energy from food affects lifespans is supported in that one of the few ways known to extend lifespan is to massively restrict calorie intake. Eating less reduces the calories burnt and the body’s exposure to less oxidative stress, but it may feel close to starving!

Free Radicals

Oxidative stress doesn’t just speed up the ageing process, it can challenge fertility and is particularly a problem when: i

  • There are many free radicals” or other types of reactive oxygen species (ROS) that damage cells
  • The ability to repair the damage they cause is low

Healthy bodies have a relative balance between oxidative stress levels and their body’s repair system. Because oxidation in cells is unavoidable (but damaging if uncontrolled), we’ve evolved ways to prevent or reduce free radicals. These involve enzymes and antioxidants that are part of a constant repair process that maintain the health of our cells.

Because the DNA carries the “code” for how cells function and organs perform, any damage to it is very bad news. The DNA in cells influence how long they live, and short-lived animals have significantly more oxidative damage in their cells:

  • Humans have 10,000 to 11,500 incidents of oxidative damage per cell each day (lifespan 67-78 years)
  • Rats have 74,000 to 100,000 incidents of oxidative damage per cell each day (lifespan 2-5 years) ii iii

Some people have genetic conditions (such as the ERCC3 gene) that reduce their ability to repair DNA, and their lives are shorter because of this.

Age and oxidative stress

For all of us, oxidative stress becomes more important as we get older, simply because:

  • The amount of oxidative stress from free radicals increases with age iv
  • Our ability to repair the breaks in the DNA reduces as we get older v

This combination of factors (increased oxidative damage to cells and a less effective repair system) is an important part of why:

  1. Fewer eggs survive to reach the last stages of folliculogenesis in older women
  2. The accelerated fall in women’s ovarian reserve after the age of 35 (eggs and age)
  3. The higher rates of sperm DNA fragmentation seen in older men

Just how much oxidative stress a person’s eggs or sperm are exposed to depends on their lifestyle choices (smoking, drugs, diet, alcohol etc) and their constitutional ability to tolerate and repair the damage. The lifestyle choices that parents make don’t just affect their health and fertility; it affects the fertility health of their children. Girls of parents with high oxidative stress levels form fewer eggs as they grow in the womb and have less fertile years as adults, and boys of women who drink during pregnancy are less fertile in their 20’s. vi vii

Men and women

Egg and sperm cells are especially vulnerable to oxidative damage as they have single (rather than double) strands of DNA, which makes them less stable or able to repair any damage they have. Women have a set number of eggs upon reaching puberty, and each month a new batch is recruited towards ovulation in a process that takes about 13 months. Very few of the tens of thousands of eggs survive the recruitment process and reach the ovulation stage. This is principally because the follicles that surround each egg must grow and develop dramatically during the recruitment process. Growth requires a lot of energy (and oxidation), which being so close to the delicate egg cell can cause a lot of harm.

Sperm only take about 90 days to fully mature, but usually, only a few percent are viable, which is why so many are needed. Healthy sperm samples have lower oxidative stress levels and higher antioxidant levels. In fact, testing semen for antioxidant levels is a more accurate way to predict fertility than counting the number of viable sperm in it! viii

Low levels of antioxidants are linked to a number of important female fertility conditions: ix

Just supplementing with antioxidant omega-3 fatty acids can extend a woman’s childbearing years and improve egg quality, even when it’s only done for a short time. x

Improve oxidative stress levels

Test to see how oxidative stress is affecting your health and fertility:

  1. Test your oxidative stress levels
  2. Test your nutritional need to ensure your body has the right levels of antioxidants

You can also pro-actively support your fertility and the health of eggs and sperm by:

  1. Reducing lifestyle choices that increase oxidative stress
  2. Adding lifestyle choices that lower oxidative stress:
    • Follow the advice for your Personal Fertility Profile (PFP)
    • Follow the advice for any health condition you have
    • Supplement with sensible antioxidants
    • Get enough sleep
    • Choose a therapy that improves fertility and reduces oxidative stress, such as herbal medicine xi


Photo by Marek Piwnicki on Unsplash