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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 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, or the fire can spread or it creates carbon monoxide and other toxic chemicals.

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 one of the few ways known to extend lifespan is to massively restrict calorie intake supports this idea as eating less reduces the calories burnt and the body’s exposure to less oxidative stress, but it may feel like years of being 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, which involve enzymes and antioxidants that are part of a constant repair process that maintains health.

Because DNA carries the “code” for how cells function, and organs perform, any damage to it is very bad news. DNA in cells influences many aspects of life, 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 65-85 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 inevitably 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 reach the last stages of folliculogenesis in older women
  2. Women’s ovarian reserve falls more rapidly after the age of 35 (eggs and age)
  3. Older men have higher rates of sperm DNA fragmentation

How much oxidative stress a person’s eggs or sperm are exposed to varies with 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 while grow ing in the womb and have less fertile years as adults, while boys of women who drank alcohol during their pregnancy are less fertile in their 20’s. vi vii

Men and women

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

Sperm take about 90 days to form and become mature, but usually, only a few percent are viable, which is why many tens of thousands are needed. Healthy sperm samples have low oxidative stress levels and high antioxidant levels, and testing semen for antioxidant levels is a more accurate predictor of fertility than the number of viable sperm. viii 

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

Simply 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

It’s possible to test oxidative stress to gauge its effect on health and fertility:

  1. An oxidative stress test
  2. A nutritional assessment that measures metabolic pathways and the essential antioxidants involved in them

Pro-actively support 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:
    • Following PFP advice
    • Follow the advice for relevant health conditions
    • Supplement with sensible antioxidants
    • Get enough sleep
    • Choose a therapy that raises fertility and reduces oxidative stress, such as herbal medicine xi


Photo by Marek Piwnicki on Unsplash