The fertility benefits of Brazil nuts stem from their selenium content, a mineral that can improve sperm quality, protect against oxidative damage, and boost the production of thyroid hormones, which are essential for fertility . A scientific review suggests that moderate intake of selenium mineral can improve reproductive efficiency in both men and women 
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Effects of Brazil nuts on men Fertility
A study published in the journal Fertility and Sterility found that men with higher levels of selenium in their sperm had better sperm quality than men with lower levels of selenium .
Also, a result from one study on 143 men 18–53 years carried out at the Andrology Centre of Tartu University Hospital from May 2009 to March 2010, suggests that antioxidant depletion and deficiency of selenium and zinc can lead to lower sperm quality which causes male infertility .
This means dietary supplementation of micronutrients like selenium can improve male fertility. There is more evidence supporting the fertility benefits of Brazil nuts which is attributed to its selenium content that has been linked with improved fertility [5, 6, 7].
Effects of Brazil nuts on Female fertility
A recent systematic review on the influence of selenium in female fertility, suggests that intake of selenium-rich food like Brazil nuts can improve women’s reproductive efficiency and reduce the risk of miscarriage .
Another study found that women with higher levels of selenium in their blood were more likely to get pregnant than women with lower levels of selenium .
5 Fertility benefits of Brazil nuts
Brazil nuts are loaded with both micro and macronutrients that can boost reproductive efficiency in both men and women. Here are some of the fertility benefits of Brazil nuts:
- Protects against oxidative damage
- Fights inflammation
- Improves sperm quality
- Can Increase chances of conception
- May lower the risk of miscarriage
Some of the essential nutrients in Brazil nuts that are important for fertility, are selenium, vitamin E, magnesium, and zinc.
- Vitamin E is an antioxidant that helps protect cells from damage.
- Magnesium is involved in the production of sex hormones.
- Zinc is important for sperm production.
Protects against oxidative damage.
Oxidative stress has been proven detrimental to fertility and reproductive health as it may lower the quality of reproductive gametes resulting in infertility.
Improves sperm quality
Here is another evidence that Brazil may improve sperm quality and testosterone production in men.
A 26-week study of 468 men found that taking 200 micrograms (mcg) of selenium daily along with 600 milligrams (mg) of N-acetylcysteine increased testosterone production, sperm count, and sperm quality compared to a placebo group .
Another study of 690 men found that taking 200 mcg of selenium daily along with 400 international units (IU) of vitamin E for 100 days improved sperm motility and appearance in 53% of participants, and 11% of men were able to get their partners pregnant .
This means intake of Brazil nuts may improve sperm quality in infertile men due e the presence of Selenium, but high intake may hurt motility.
Can Increase chances of conception
However, experts have also warned against excessive intake of selenium-rich food due to the potential downside of high selenium in our system 
May lower the risk of miscarriage
Selenium is an antioxidant that helps protect cells from damage. This can help to protect against miscarriage, which is often caused by cell damage.
A supporting study revealed that a sufficient amount of selenium present both in couples will offer them better reproductive health and for pregnant women, it boosts fetal development .
The Side Effects of Brazil nuts for fertility
It is important to note that Brazil nuts are also high in calories and fat. Therefore, it is important to consume them in moderation.
For instance, selenium which is abundant in Brazil nuts can be both beneficial in moderate amounts and detrimental In high amounts .
The recommended daily intake of selenium is 55 micrograms for men and 40 micrograms for women. A single Brazil nut contains about 95 micrograms of selenium.
This means excessive intake can lead to selenium overdose, which can cause hair and nail loss or brittleness, nausea, diarrhea, skin rashes, mottled teeth, fatigue, irritability, and nervous system abnormalities .
High in calories and fat
Brazil nuts are high in calories and fat. Therefore, it is important to consume them in moderation.
Can interfere with thyroid function
May increase the risk of diabetes
Some studies have found that too much selenium, particularly from supplements, may lead to high blood sugar resulting in a higher risk of diabetes [38, 39]. While some studies suggest it may increase the risk of cancer .
May cause allergic reactions
Brazil nuts can cause allergic reactions in some people. Symptoms of an allergic reaction can include hives, itching, and swelling.
Overall, Brazil nuts are a good source of nutrients that are important for fertility. However, it is important to consume them in moderation and to be aware of the potential downsides.
If you are considering taking Brazil nuts to improve your fertility, it is best to talk to your doctor first. They can help you determine if Brazil nuts are right for you and can advise you on how to take them safely.
JC is passionate about finding the impact of foods (feeding habits) on human fertility and reproductive health and a way to improve fertility.