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Lack of zinc harms your fertility

- and has a long-term effect on the maturation of a woman’s eggs

Lack of zinc harms your fertilityIt is well established that zinc is important for the maturation of the eggs in the fallopian tube during a woman’s menstrual cycle. However, a new American study has shown that zinc is involved in even earlier stages of the maturation of the eggs. A zinc deficiency therefore reduces the chance of the eggs being fertilized and dividing later on, which they are supposed to during pregnancy. Lack of zinc is rather common and may harm your fertility for several months to come.

Around one in ten couples in the United States is childless. In Denmark, it is one in seven couples. For many women, it is a race against time, as their biological clock keeps ticking away. There may be a number of reasons why a woman is unable to conceive. Complications during her ovulation is one of the best known reasons why a woman cannot get pregnant. However, scientists from Pennsylvania State University in the United States have now discovered that a zinc deficiency may be harmful to the eggs during the early part of their maturation. This may have long-term consequences for a woman’s ability to conceive.
Apparently, zinc deficiencies are rather common. For one, sugar, inorganic iron supplements, and birth control pills can impair the uptake of zinc in the body. Secondly, it may be difficult to get enough zinc from a vegetarian or vegan diet. The lack of zinc harms not only a woman’s fertility but even other enzyme processes that depend on zinc.

Under normal circumstances, eight out of 10 women conceive within the first year of having unprotected sex. Couples who try to conceive for more than one or two years without luck are considered childless.

A woman’s eggs must be fully matured and in top-notch condition when she ovulates

The presence of micronutrients such as zinc and selenium are essential for fertility. At birth, a girl’s ovaries contain around two million eggs, while only around 400 eggs reach maturity after her puberty. Each immature egg is surrounded by a wreath of cells called the follicle. During the first half of a woman’s menstrual cycle, the pituitary hormone FSH (Follicle-Stimulating Hormone) stimulates several of these follicles to mature the eggs. Normally, only one egg follicle reaches complete maturity. FSH also stimulates the follicles to step up their production of estrogen, which causes a swelling of the uterus, which enables it to receive a fertilized egg.
After 14 days, the production of FSH decreases, while the production of LH (Luteinizing Hormone) goes up. This hormone causes the mature follicle to burst and expel the mature egg, which is then intercepted by the fallopian tube. A few days later, it reaches the uterus. After ovulation, cells start to grow inside the ruptured follicle sac. They eventually become what is known as the corpus luteum – or the yellow body. At this point, the body starts to produce progesterone, the hormone that enables the fertilized egg to attach to the uterus and helps the pregnancy proceed. At the same time, there is a thickening of the uterine mucosa.
If, however, the egg is not fertilized, the mucosa is rejected, and the menstrual period begins. Needless to say, the woman’s egg must be fully matured and in excellent condition, but there are other factors that can prevent the immature egg cell from developing normally before the egg is released during ovulation and is ready to be fertilized by a sperm cell.

The first time ever that researchers test egg quality in the early stages

Previous studies of female fertility have focused on the large egg follicles and their ability to mature under the influence of follicle-stimulating hormone from the pituitary gland. More and more evidence points to zinc as being of vital importance for egg quality a long time before the egg matures. In other words, the size of the egg follicles alone is not a useful parameter for egg quality. In the new study from Pennsylvania State University, James Hester and his team of scientists looked at the smaller pre-follicles, which have to grow for around 90 days before they are ready for ovulation. Earlier studies have shown that zinc levels are determining for the development of egg follicles during the 14-day period prior to ovulation. However, it is the first time that scientists test egg quality during the early stages of development, which unfold several months before ovulation.

Zinc is primarily found in liver, meat, fish, shellfish, dairy products, seeds, kernels, and beans. Zinc from animal sources is absorbed a lot better than zinc from plant sources.

Early egg defects were observed, even when zinc was supplied

James Hester and his research team collected immature egg follicles from mice, which they then matured in two different cell cultures with either adequate amounts of zinc or too little zinc.
The researchers then compared the egg follicle maturation in the two different cell cultures. At the same time, they exposed the egg follicles to various hormonal influences to emulate the natural maturation of egg follicles.
The scientists found that lack of zinc in the early part of the egg follicles’ maturation resulted in:

  • Disturbances in the development of follicle cells in the cell culture
  • Smaller egg zinc at the early stage of maturation
  • Cell marker problems
  • Impaired ability of the eggs to divide (meiosis), which is a vital step before successful fertilization
  • The observed defects prevailed even after adding more zinc to the cell culture.

Even marginal zinc deficiencies can affect the quality of eggs

Animal studies have shown that zinc is important for fertility and fetal development, but the new study is the first to show that zinc is essential for the quality of eggs several months prior to ovulation and for fertilization to happen. According to WHO, 17 percent of the global population is deficient in zinc. This does not include borderline zinc deficiency, where people get zinc from the diet but not enough to reach the officially recommended intake of 10 mg (also known as the reference intake level or RI).
Because zinc is a trace element that is involved in around 300 different enzyme processes, a marginal zinc deficiency can easily disturb those enzyme processes that deal with maturation of egg follicles and fertility in general. As mentioned earlier, too much sugar, inorganic iron supplements, and birth control pills impair the body’s uptake of zinc, and it is difficult to get enough zinc if you are a vegetarian or vegan.

Deficiencies and poor utilization of zinc may be a result of

  • poor diet and lack of animal protein
  • too much sugar
  • large consumption of iron and calcium
  • excessive sweating
  • alcohol and alcohol-related liver ailments
  • gluten intolerance (celiac disease)
  • irritable bowel and Crohn’s disease
  • birth control pills and diuretics
  • prolonged use of antibiotics (tetracycline)

Measuring zinc levels and using supplements

It is easy and inexpensive to measure zinc levels in plasma. A detected zinc deficiency is corrected with zinc supplements, depending on the deficiency level and the patient’s diet. Borderline zinc deficiency can be treated with 15-30 mg of zinc supplementation daily. Moderate to severe zinc deficiency requires daily supplementation with up to 45 mg of zinc (no longer than four months). When treating a zinc deficiency, it is important to continue supplementing for some time after the zinc concentration has been normalized, as most of our zinc is concentrated in various tissues and not in the blood.


Preconception zinc deficiency could spell bad news for fertility. American Physiological Society April 2018


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