Thanks to advances in assisted reproductive technology, many couples with fertility problems turn to procedures such as in-vitro fertilization (IVF) to successfully conceive a child. IVF now accounts for about 1-3% of births in the US, equating to roughly 60,000 newborn babies each year.¹ Because IVF comes at a high cost and has a relatively low success rate as women age, many couples are looking to increase the likelihood of success by incorporating dietary and lifestyle strategies.^1,2 In this article, we are going to discuss how the aging process affects a woman’s reproductive capacity, and whether carnitine supplementation can help address age-related fertility changes in a way that supports IVF success. 

The Effects of Aging on Women’s Reproductive Capacity

A woman’s chances of getting pregnant decrease significantly after the age of 35, primarily due to falling hormone levels and the ovaries’ diminished capacity to produce eggs of adequate number and quality.^3,4 What’s more, mitochondrial function in the eggs and ovaries rapidly declines with advanced maternal age.^3,4 As you may recall from biology, mitochondria act as the “powerhouses” of the cell, and are responsible for generating energy in the form of ATP.

Pregnancy is an energy-demanding process that requires a tremendous amount of ATP. As a woman’s mitochondrial function diminishes with age, her ATP production declines, which ultimately lowers her reproductive capacity. And, indeed, impaired mitochondrial function within a woman’s eggs and ovaries has been linked to lower fertilization rates, pregnancy rates, embryo quality, and rates of embryo implantation.^5,6

Why might a decline in mitochondrial function negatively affect a woman’s reproductive cells? 

Mitochondria are called the “powerhouses of the cell” because they break down a variety of nutrients to make sure that the cell has sufficient energy.⁷ Female sex gametes (otherwise known as egg cells or oocytes) represent the largest cell in a woman’s body and contain the highest number of mitochondria per cell.⁴

Mother nature designed oocytes to be jam-packed with mitochondria because these reproductive cells need massive amounts of energy to carry out important reproductive tasks like egg maturation, fertilization, and embryonic development.^8,9 Indeed, many human studies have shown that eggs with higher amounts of mitochondrial energy have a greater potential for normal embryonic development and successful implantation.^10,11

What are some of the ways aging impacts mitochondrial function? 

Women over the age of 35 tend to have abnormal mitochondrial “swelling,” which may reduce their capacity for energy production during the critical stages of egg maturation.^12,13 Aging women also tend to have higher amounts of damaged mitochondria in cells surrounding the egg—yet another factor linked to poor embryo quality and ovary function.^14,15

But wait! Before you start stressing about all of these age-related changes in reproductive function, know that there are things you can do to help neutralize the effects of age-related changes. For example, emerging evidence suggests that certain nutrients, such as omega-3 fatty acids, vitamin D, CoQ10, and carnitine may help promote fertility and successful birth outcomes.^16,17

Does Carnitine Support the Success Rates of IVF?  

Decades of research show that carnitine, a compound found in animal proteins and synthesized in the human body to help support cellular health and energy production, plays a vital role in fertility.¹⁸ Given its important role in energy metabolism, carnitine is required by virtually every cell in the body. Mitochondria also exist in most cells of the body and are heavily dependent on carnitine to make ATP—a source of energy required for the development of oocytes and embryos.¹⁹ Carnitine also supports mitochondrial function by eliminating the buildup of molecules that can become toxic to mitochondria, stabilizing mitochondrial membranes, and helping protect against mitochondrial death.^20,21

Yet another way that carnitine can promote health is by addressing oxidative stress. Similar to the rusting that happens in pipes from oxidation, oxidative stress occurs when there is an imbalance between the free radicals and antioxidants in the body. In addition to other health complications, oxidative stress is known to negatively impact male and female fertility, as well as the success of IVF.²² Fortunately, some research shows that carnitine supplementation can help address oxidative stress.²³

Because carnitine has been shown to have many fertility-supporting qualities, researchers have started to explore how carnitine supplementation could impact fertility.^17,24 A recent study (2018) evaluated the effects of carnitine on embryo quality and birth outcomes by comparing groups of women who had IVF procedures completed with or without carnitine added to the IVF solution.¹⁷ The results showed that women in the carnitine group had higher quality embryos, implantation rates, and pregnancy rates as compared to the group without carnitine. 

Another recent trial evaluated the effects of oral carnitine supplementation in women who had previously failed to conceive using IVF methods.²⁴ In this trial, the women were assigned to take carnitine supplements for an average of three months before repeating their IVF treatment. The results indicated that, after taking carnitine supplements, women were more likely to have healthier embryos, to conceive successfully, and to have successful births than when using IVF without carnitine supplementation. These findings suggest that higher quality embryos are more likely to implant and result in a pregnancy brought to full term–and that carnitine may help facilitate the process. 

Conclusion

In summary, we know that as a woman ages, her mitochondrial function starts to progressively decline, resulting in a loss of capacity to produce enough energy to carry out reproductive functions optimally. This can affect a couple’s chances of conceiving, even with the help of assisted reproductive technology such as IVF. Additionally, it appears a poor carnitine status can impair mitochondrial function, compounding this problem further. 

Fortunately, the latest research shows that carnitine supplementation can promote the success of IVF by supporting embryo quality, embryo attachment to the uterus, pregnancy rates, and successful birth rates. We encourage those seeking fertility-supportive nutritional strategies to consult with their doctor about whether carnitine supplementation may help.