Higher zinc intake may increase endometriosis risk

Loads of freshly caught fish, a source of zinc, on a counter Too much zinc could be linked to several health issues, including higher endometriosis risk. Duet Postscriptum/Stocksy

Zinc is an essential mineral that supports immune function, hormone balance, and cell growth.
In contrast with previous studies, new research suggests that higher zinc consumption may significantly increase the risk of endometriosis compared to consuming lower amounts.
Experts recommend following current zinc guidelines, ensuring adequate intake without excess, and consulting a professional for guidance as needed.

A recent study suggests a potential link between higher dietary zinc intake and increased risk of endometriosis in American women compared to those with lower zinc consumption.

Zinc is a trace mineral essential for numerous bodily functions, from insulin production to immune system health. It also plays a role in hormone regulation, DNA and protein synthesis, and cell division and growth.

Our bodies cannot store zinc, so we must obtain it through our diet. However, maintaining the right balance is key, as both too much and too little zinc can disrupt human physiology.

Research has begun to explore zinc’s impact on women’s reproductive health, though our understanding is limited, especially regarding conditions like endometriosis.

This chronic condition involves endometrial cell growth outside the uterus, affecting about 6–10% of women of reproductive age. Endometriosis often leads to pain and potential complications like infertility, which impacts up to 50% of those diagnosed.

The findings of this study are published in BMC Public HealthTrusted Source.

“This study provides important insight into the possible physiologic mechanism of zinc’s role in the development of endometriosis,” said Alexandra Filingeri, DCN, RDN, a doctor of clinical nutrition and certified fertility dietitian, who was not involved in the study, to Medical News Today.

Studying dietary zinc intake and endometriosis risk

The current study involved a secondary analysis of data collected from the National Health and Nutrition Examination SurveyTrusted Source conducted between 1999 and 2006, focusing on American women ages 20 to 54.

Participants self-reported their endometriosis diagnosis in a reproductive health questionnaire and documented their dietary zinc consumption by providing 24-hour recalls of their food intake.

Researchers assessed one of these 24-hour recalls to estimate each participant’s usual dietary zinc consumption.

They also considered various factors that could influence the results, including medications and dietary supplement use, age, body mass index, physical activity levels, smoking status, and more.

A total of 4,315 women were included in the final sample, and 331 (7.7%) of them reported being diagnosed with endometriosis.

In terms of demographics, approximately 64% of participants were classified as overweight, 39.4% identified as smokers, and 47% reported using dietary supplements.

The age distribution showed that about 53% were younger than 40, 33% were between 40 and 50, and 14% were older than 50.

The researchers conducted multiple statistical analyses to examine the relationship between zinc intake and the risk of endometriosis while considering these various influencing factors.

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Higher dietary zinc intake may increase endometriosis risk

Women who took dietary supplements, exercised moderately, and lived with a partner or had a higher income tended to consume more zinc in their diets.

Interestingly, the researchers initially hypothesized that higher dietary zinc would lower the risk of endometriosis.

However, they found that higher zinc intake might increase the chance of developing endometriosis.

Women who consumed over 14 milligrams (mg) of zinc daily appeared to have a 60% higher risk of endometriosis compared to those who consumed 8 mg a day or less.

They observed no statistically significant change in endometriosis risk among those consuming 8 to 14 mg of zinc daily.

Additional analysis revealed that lifestyle or demographic factors like smoking, obesity, or race did not seem to influence the link between higher zinc intake and endometriosis risk.

Filingeri highlighted that “this research challenges some of the previous literature discussing zinc’s role in reproductive health,” which has reported lower zinc levels in women with endometriosis.

The authors suggest this difference might be due to how zinc is absorbed and metabolized in studies that look at blood versus urine levels or because earlier studies included smaller sample sizes.

However, Filingeri indicated that one major limitation of this study is its retrospective nature, as it relied on dietary recall rather than monitoring zinc intake over time.

Ultimately, this observational study can’t prove cause and effect, and more research is needed to understand zinc’s role in endometriosis and women’s reproductive health.

How might zinc contribute to endometriosis?

Zinc may play a role in endometriosis by managing the body’s immune responses and reducing oxidative stress, which might contribute to developing endometriosis.

It also helps control enzymes called matrix metalloproteinases (MMPs), which are important for tissue repair and growth.

StudiesTrusted Source suggest women with endometriosis might have higher levels of certain types of these enzymes, specifically MMP-2 and MMP-9.

Eliza Whitaker, MS, RDN, a women’s health dietitian and founder of Nourished Nutrition and Fitness, who was not involved in the study, said that these enzymes might contribute to the spread of endometriotic tissue outside its typical location.

She explained that as these MMPs break down the extracellular matrix (surrounding tissue structure), they promote the release of certain inflammatory molecules and help endometrial cells spread into nearby tissues.

However, she noted, we think this happens when zinc levels are lowTrusted Source.

“Another [potential] mechanism involves a protein that binds zinc after it’s absorbed in the diet, metallothionein,” Whitaker said.

As people age or when they have chronic inflammation, the amount of metallothionein in the body tends to rise. When metallothionein traps zinc, less zinc is available to help certain enzymes work and block MMPs.

Additionally, “while low zinc availability poses a concern, high zinc availability may result in immunosuppression,” added Filingeri.

This is relevant because endometriosis has been linked to immune dysfunctionTrusted Source and chronic inflammation.

Finally, Whitaker pointed out that high zinc may also “influence endometriosisTrusted Source by acting as a metalloestrogen, or a metal [ion] that binds and stimulates estrogen receptors.”

Endometriosis is an estrogen-dependent condition, meaning it relies on estrogen for its growth and progression. Therefore, zinc in high doses might be an endocrine disruptor, upsetting the body’s hormone balance. This may potentially encourage the development and spread of endometriosis.

Essentially, there are many theories, and we have yet to fully grasp the complex relationship between zinc and endometriosis.

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Advice for women on how to consume enough zinc

Zinc needs may vary among women based on factors like dietary habits and health status.

The study suggests that around 8 mg of zinc daily from food could be a suitable target for most non-pregnant women, potentially lowering the risk of endometriosis compared to higher intakes.

This aligns with current National Institutes of Health (NIH) Office of Dietary SupplementsTrusted Source guidelines advising women who are not pregnant to aim for a daily zinc intake of 8 mg. The recommended daily intake for a pregnant person increases to 11 mg of zinc.

To meet your daily goals, obtain zinc from a variety of whole food sourcesTrusted Source, such as:

beef (bottom sirloin, roasted, 3 oz: 3.8 mg zinc)
pumpkin seeds (roasted, 1 oz: 2.2 mg zinc)
turkey breast (cooked, 3 oz: 1.5 mg zinc)
lentils (boiled, half cup: 1.3 mg zinc)
plain Greek yogurt (6 oz: 1 mg zinc)

Oysters are an especially rich source of zinc, containing “anywhere from 28.1 to 32 mgTrusted Source of zinc per 3 oz serving, which is double the 14 milligrams a day referenced in this study,” Whitaker noted.

She cautioned that zinc supplements might cause excessive zinc levels if your diet already provides sufficient amounts.

So, be mindful of your dietary zinc intake and avoid zinc supplements unless recommended by a doctor or registered dietitian.

Whitaker also suggests checking the zinc content in any supplements you take, as you may unknowingly consume it from multiple sources.

Although diet seems to affect the development of endometriosis, it’s not the sole determinant. Genetics, the immune system, gut microbiota, and environmental factors might also play a role.

Talk with your doctor or gynecologist if you have concerns about your risk for this condition.