Cucumber

Health Benefits
(Source: World's Healthiest Foods, George Mateljan)

Broad-Spectrum Nutrient Richness from Cucumbers

Cucumbers have not received as much press as other vegetables in terms of their overall nutrient richness, but this long-beloved food provides us with a unique combination of conventional nutrients and phytonutrients. In terms of conventional nutrients, we are talking about a food that rises high in our WHFoods rating system with two excellents (for vitamin K and the mineral molybdenum), one very good (for the B vitamin, pantothenic acid), and 8 goods (for vitamin C, vitamin B1, and biotin in the vitamin category and for copper, magnesium, manganese, phosphorus, and potassium in the mineral category).

But the nutrient richness of cucumbers may be especially surprising when it comes to phytonutrients. Researchers have now identified 73 different phenolic compounds in cucumbers that are likely to provide us with antioxidant and anti-inflammatory benefits! The bulk of the research on cucumber phytonutrients focuses on three specific categories: flavonoids, lignans, and terpenoids. Below is a summary list of key phytonutrients in these three categories.

Flavonoids

  • apigenin

  • diosmetin

  • fisetin

  • luleolin

  • quercetin

  • kaempferol

  • luteolin

  • naringenin

  • theaflavanoside I

  • vicenin

Lignans

  • pinoresinol

  • lariciresinol

  • secoisolariciresinol

Triterpenes

  • cucurbitacin A

  • cucurbitacin B

  • cucurbitacin C

  • cucurbitacin D

Details about the best-researched health benefits of cucumbers are provided in the paragraphs below.

Antioxidant & Anti-Inflammatory Benefits of Cucumbers

Among all of the phytonutrients listed above, the vast majority have been shown to have antioxidant and/or anti-inflammatory properties either directly or through their influence on enzymes or metabolic pathways. For example, cucumber extracts inhibit the activity of cyclo-oxygenase 2 (COX-2), a well-studied pro-inflammatory enzyme. The activity of antioxidant enzymes - including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH) - has also been show to increase in the bloodstream of participants who consumed cucumber power. Cucumbers also contain fisetin - a flavonoid that has been of special interest to researchers not only because of its antioxidant and anti-inflammatory properties but also because of its potential for risk reduction in the case of certain cancer types. While cucumbers contain fisetin in a lower concentration than onions, strawberries, apples, or grapes, they are still an important source of this flavonoid.

The antioxidant benefits of cucumbers have also been studied in the context of type 2 diabetes. The metabolism of individuals diagnosed with type 2 diabetes can sometimes become subject to changes that involve excessive formation of reactive molecules in certain cells. Reactive oxygen species (ROS) and reactive carbonyl species (RCS) are two such molecules that can be formed in excessive amounts. Several recent studies have shown the ability of cucumbers to help reduce production of ROS and RCS.

While still in its early stages (and mostly based on animal studies), research on cucumbers has been focusing more and more on alleviation of problems related to blood sugar regulation. When our blood sugar levels remain too high over a long period of time, we see increases in ROS and RCS that can damage cell structures and body components. Increased intake of cucumber holds promise as a step for significantly lessening this overproduction of ROS and RCS. Researchers believe that a wide variety of phenolic compounds in cucumbers are likely to be involved in this potential health benefit, including its many flavonoids and terpenoids.

Other Potential Health Benefits from Cucumbers

Most of the research that we have seen on cucumbers and chronic disease risk have focused cardiovascular system problems, type 2 diabetes, and development of cancer. In all three areas, we consider the research to be preliminary, and much of it has been based on animal studies. There are logical theoretical connections between a food like cucumber that is rich in antioxidant and anti-inflammatory phytonutrients and risk of problems in each of the areas described above. In addition, specific phytonutrients in cucumbers have been tested in small-scale human studies and found to provide some of the health benefits described above.

Two examples in the area of cancer research are especially interesting. Scientists now know that cucumber lignans like lariciresinol, pinoresinol, and secoisolariciresinol can be converted by bacteria in our digestive tract into enterolignans like enterodiol and enterolactone. These enterolignans can bind onto estrogen receptors where they can have both pro-estrogenic and anti-estrogenic effects. In some preliminary studies, decreased risk of estrogen-related cancers - including certain cancers of the breast, ovary, uterus, and prostate - has been associated with intake of dietary lignans from a variety of different plant foods, including cucumber.

As a second example, cucumbers contain phytonutrients that are members of the terpenoid family called curcurbitacins. Cucumbers provide us with cucurbitacins A, B, C, D, and E. Researchers have determined that several different signaling pathways (for example, the JAK-STAT and MAPK pathways) associated with cancer cell development and cancer cell survival can be inhibited through the activity of cucurbitacins. Eventually, we hope to see human studies that confirm these risk-reducing benefits of cucumbers when they are consumed in a normal, everyday meal plan.

The cardiovascular benefits of cucumbers seem to involve two basic processes. First is protection of the blood vessel walls and blood constituents from oxygen-related damage. The 73 different phenolic phytonutrients identified in cucumbers - and especially its impressive array of flavonoids - appear to be central in providing this antioxidant protection. Second is the favorable impact of cucumber intake on blood fat levels, especially in individuals who have elevated blood fats. In one recent study, a small group of participants with mildly elevated blood fats consumed dried cucumber seed extracts on a daily basis over a period of six weeks and experienced a number of favorable changes in their blood fat levels. These changes included decreased total cholesterol, decreased LDL cholesterol, decreased triglycerides, and increased HDL cholesterol. We're reminded by this study not only to enjoy cucumbers for the health benefits, but to make sure and include their seeds.

In several recent studies, cucumber have been referred to as an "anti-diabetic" food, although we have yet to see a large-scale human study showing lower risk of type 2 diabetes in study participants who included cucumbers in their meal plans than in study participants who did not include this vegetable. However, what we have seen are studies showing improvement in certain metabolic problems experienced by persons with type 2 diabetes when they consumed cucumber extracts. These metabolic problems were primarily related to oxidative stress and excessive production of reactive oxygen species (ROS). Given their rich supply of antioxidant nutrients, it's not surprising to see cucumber intake resulting in this kind of improvement.

In this category of problems involving blood sugar regulation, it has also been interesting to see animal studies on fisetin - a flavonoid contained in select fruits and vegetables including cucumber. Enzymes that are need to make sugar within our liver cells (called gluconeogenic enzymes) appear to be inhibited in the presence of fisetin, thus suggesting a potential role for fisetin-containing foods (like cucumber) in support of blood sugar regulation.

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