Does Cucumber Contain Selenium? The Surprising Nutritional Fact

January 8, 2026 •

3 min read

Composed of over 95% water, the refreshing cucumber is celebrated for its hydrating properties and mild flavor. However, when it comes to the mineral selenium, the truth is that a cucumber's contribution is negligible at best.

Quick Summary

Cucumbers contain only a trace, nutritionally insignificant amount of selenium. They are not a meaningful dietary source for this essential mineral, which is found in much higher concentrations in foods like Brazil nuts, seafood, and certain meats.

Key Points

Insignificant Selenium Source: Cucumbers contain only trace amounts of selenium, making them a negligible source for meeting your daily nutritional needs.
Rich Sources Exist: Excellent dietary sources of selenium include Brazil nuts, seafood, meat, and eggs, which provide much more significant quantities.
Soil Affects Content: The selenium level in plant-based foods, including cucumbers, can fluctuate depending on the mineral content of the soil where they are grown.
Essential Mineral: Selenium is a powerful antioxidant vital for thyroid health, immune function, and protecting cells from damage.
Hydration Benefits: Cucumbers' primary nutritional value comes from their high water content and other vitamins like Vitamin K, not selenium.
Balance is Key: Maintaining a balanced intake of selenium through a varied diet is crucial to avoid both deficiency and toxicity.

The Trace Amount of Selenium in Cucumbers

While most foods contain at least some trace elements, including selenium, the quantity in a cucumber is so minimal that it is not considered a significant source. The perception that all vegetables contribute substantially to mineral intake can be misleading, especially with produce like cucumbers that are primarily composed of water.

Nutritional data from sources like the University of Rochester Medical Center and University Hospitals confirm this. A medium-sized peeled cucumber, weighing approximately 200 grams, contains a mere 0.2 micrograms (mcg) of selenium. Considering the Recommended Dietary Allowance (RDA) for selenium for adults is 55 mcg per day, you would need to consume hundreds of cucumbers to meet your daily needs, an impractical and unenviable task.

The Role of Soil in Plant Selenium Content

It is worth noting that the selenium content in plant-based foods can vary widely based on the soil composition in which they are grown. In areas with selenium-rich soil, produce may contain higher levels of the mineral. However, this is still unlikely to make a typically low-selenium vegetable like a cucumber a major source. The vast transport and distribution network for food in modern supply chains also means that the origin of a vegetable may vary, making any precise estimation of its selenium content difficult.

Why Selenium is Crucial for Your Health

Selenium is a powerful antioxidant that protects cells from damage caused by free radicals. This trace mineral is integral to many bodily functions, acting as a cofactor for enzymes involved in DNA synthesis, reproduction, and metabolism. Its role is particularly vital for the health and proper function of the thyroid gland, which contains a higher concentration of selenium than any other organ in the body. A deficiency can impact thyroid hormone metabolism and weaken the immune system.

The Dangers of Inadequate or Excessive Selenium

Maintaining a balanced intake is key, as both deficiency and toxicity can pose health risks. Selenium deficiency is rare in North America due to adequate soil levels in many regions, but it can occur in areas with poor soil content. Severe deficiency has been linked to conditions like Keshan disease, a type of cardiomyopathy.

On the other hand, excessive intake, often from over-supplementation or overconsumption of very rich sources like Brazil nuts, can be toxic. Signs of toxicity can include hair loss, brittle nails, nausea, and a garlic-like odor on the breath.

Top Dietary Sources for This Essential Mineral

If you are looking to increase your selenium intake, there are many food options that are far more potent than cucumbers. A varied diet that includes a mix of protein and grains is the most reliable way to meet your daily needs.

Here are some of the best dietary sources of selenium:

Brazil Nuts: The single richest source. Just one nut can provide more than the daily recommended intake, though concentrations can vary greatly.
Seafood: Excellent sources include yellowfin tuna, halibut, sardines, oysters, and shrimp.
Meats and Poultry: Beef, chicken breast, and turkey are good contributors to selenium intake.
Organ Meats: Beef liver, in particular, is a potent source.
Dairy: Cottage cheese and yogurt contain moderate amounts.
Grains and Beans: Whole-wheat pasta, brown rice, lentils, and baked beans all provide some selenium.

Nutritional Comparison: Cucumber vs. Selenium-Rich Foods

To put the meager selenium content of a cucumber into perspective, the table below compares its nutritional value to some common, selenium-rich food items based on approximate quantities.


Food Item	Approximate Serving Size	Selenium Content	RDA Contribution (Adults)	Notes
Cucumber (peeled, raw)	1 medium (200g)	~0.2 mcg	<1%	Mainly water; great for hydration.
Brazil Nuts	1 ounce (6-8 nuts)	~544 mcg	~989%	Extremely high; caution with overconsumption.
Yellowfin Tuna (cooked)	3 ounces	92 mcg	~167%	Excellent source of protein and selenium.
Chicken Breast (roasted)	3 ounces	22 mcg	~40%	A common, reliable source.
Hard-Boiled Egg	1 large	15 mcg	~27%	A versatile and easy source.
Brown Rice (cooked)	1 cup	12 mcg	~22%	A plant-based option.

Conclusion: Cucumbers Offer Other Benefits

In summary, while the question "does cucumber contain selenium?" can be answered with a qualified yes—in miniscule quantities—it is important to recognize that this vegetable is not a viable source for meeting your daily requirements. Cucumbers are primarily valuable for their high water content, which aids in hydration, and for providing other vitamins and minerals like Vitamin K and potassium. For adequate selenium intake, it is far more effective to focus on a balanced diet rich in proteins, seafood, and nuts, which are demonstrably superior sources.

For more information on selenium, visit the NIH Office of Dietary Supplements.

Frequently Asked Questions

Yes, cucumbers contain very small, trace amounts of selenium, but the quantity is so low that it is not considered a meaningful dietary source for the mineral.

Foods rich in selenium include Brazil nuts, yellowfin tuna, sardines, poultry, beef, and eggs. Grains like brown rice and whole-wheat pasta also contribute to intake.

A single medium-sized cucumber (around 200g) contains approximately 0.2 micrograms (mcg) of selenium, which is less than 1% of the adult daily recommended intake.

Yes, cucumbers are primarily known for their high water content, which promotes hydration. They also contain other nutrients, including Vitamin K and potassium.

A selenium deficiency is not caused by eating cucumbers, but rather by not consuming enough selenium-rich foods. Relying on cucumbers as a primary food source would not provide sufficient selenium.

Excessive selenium intake, or selenium toxicity, is rare but can cause symptoms like hair loss, brittle nails, fatigue, nausea, and a garlic-like breath odor.

To naturally increase your selenium intake, incorporate more nuts (especially Brazil nuts), seafood, meat, poultry, and eggs into your diet. A varied diet is the best approach.