Bitter greens are peppers-flavored greens that come from the mustard plant (Brassica juncea L.) (1).
Also known as brown mustard, herb mustard, Indian mustard, and Chinese mustard, mustard greens are members of the Brassica vegetable family. This genus also includes kale, collard greens, broccoli and cauliflower (2, 3).
There are several varieties that are usually green in color and have a strong bitter, spicy flavor.
To make them more beautiful, these leafy greens are usually enjoyed boiled, steamed, fried or even pickled.
This article provides a complete overview of mustard, including its nutrition, benefits and uses.
Nutritional profile
Mustard is one of the most nutritious foods you can eat, because it is low in calories, yet rich in fiber and micronutrients (4).
One cup (56 grams) of chopped raw mustard provides (4):
- Calories: 15
- Proteins: 2 grams
- Fat: less than 1 gram
- Carbohydrates: 3 grams
- Fiber: 2 grams
- Sugar: 1 gram
- Vitamin A: 9% daily value (DV)
- Vitamin B6 (pyridoxine): 6% DV
- Vitamin C: 44% DV
- Vitamin E: 8% DV
- Vitamin K: 120% DV
- Copper: 10% DV
In addition, mustard greens contain 4–5% DV for calcium, iron, potassium, riboflavin (vitamin B2), magnesium, and thiamin (vitamin B1), as well as small amounts of zinc, selenium, phosphorus, niacin (vitamin B3), and folate (4).
Compared to raw mustard, one cup (140 grams) of cooked mustard has much higher levels of vitamin A (96% DV), vitamin K (690% DV), and copper (22.7% DV). However, it is lower in vitamins C and E. (5).
Pickled mustard greens, often called takana in Japanese and Chinese cuisine, are similar in calories, carbohydrates and fiber to raw mustard. But they lose some nutrients during the sour taste, especially vitamin C (6).
However, one study found that acidic acid is an effective method for retaining important plant compounds with antioxidant properties (7).
Health benefits of mustard
Currently, there is limited research on the specific benefits of eating mustard.
However, individual nutrients found in mustard greens—and Brassica vegetables in general—are linked to numerous health benefits.
It is rich in antioxidants that fight disease
Antioxidants are natural plant compounds that help protect against oxidative stress caused by excess free radicals (8).
Free radicals are unstable molecules that can damage your cells. Research shows that over time, this damage can lead to serious, chronic conditions, such as heart disease, cancer, and Alzheimer's disease (8, 9).
Although the levels of specific antioxidants vary between different varieties of mustard, these leafy greens are generally a rich source of antioxidants such as flavonoids, beta carotene, lutein, and vitamins C and E (1, 3, 4, 10).
In addition, red varieties are rich in anthocyanins, red-purple pigments found in fruits and vegetables that are associated with a reduced risk of heart disease, cancer and type 2 diabetes (1, 11).
Overall, including mustard in your diet may help protect against oxidative stress-related diseases.
An excellent source of vitamin K
Both raw and cooked mustard greens are a phenomenal source of vitamin K, providing 120% and 690% of the DV per cup (56 grams and 140 grams), respectively.4, 5).
Vitamin K is best known for its vital role in helping blood clot. It has also been shown to be essential for heart and bone health (12).
In fact, inadequate vitamin K is associated with an increased risk of heart disease and osteoporosis, a condition that results in reduced bone strength and an increased risk of fractures (13, 14).
Recent studies have also suggested a link between vitamin K deficiency and brain health. Inadequate vitamin K may be associated with an increased risk of impaired brain function, dementia, and Alzheimer's disease. However, more research is needed (15, 16).
Can it increase immunity?
Bitter greens can also be good for your immune system.
Just one cup (56 grams raw, 140 grams cooked) provides more than a third of your daily vitamin C needs (4, 5).
Vitamin C is a water-soluble vitamin that is essential for a strong immune system. Research shows that getting enough vitamin C in your diet can weaken your immune system, making you more susceptible to getting sick (17).
Additionally, the vitamin A in mustard greens also supports your immune response. It does this by promoting the growth and distribution of T-cells, which are a type of white blood cell needed to help fight potential infections (18, 19).
May benefit heart health
Mustard greens may also be good for your heart.
They are full of antioxidants such as flavonoids and beta carotene, which are associated with a reduced risk of developing and dying from heart disease (20, 21, 22).
One review of eight studies found that a high intake of brassica leafy green vegetables was associated with a significant 15% reduced risk of heart disease (23).
As with other Brassica vegetables, mustard greens contain compounds that help bind bile acids in your digestive system. This is important, because preventing the reabsorption of bile acids leads to lower cholesterol levels (24).
According to one test tube study, mustard greens vapors significantly increase the binding effect of bile acids. This suggests that mustard seeds may have greater cholesterol-lowering potential compared to eating them raw (25).
It can be good for eye health
Antioxidants in mustard include lutein and zeaxanthin, which have been shown to have beneficial effects on eye health (1, 4, 26, 27).
These two compounds in particular help protect the retina from oxidative damage and remove potentially harmful blue light (26, 27).
As a result, research shows that eating foods rich in lutein and zeaxanthin can help protect against age-related macular degeneration, the world's leading cause of blindness (26).
It can have an anti-cancer effect
In addition to powerful antioxidants, which can have an anti-cancer effect, bitter greens are high in a group of beneficial plant compounds called glucosinolates (1).
In test-tube tests, glucosinolates have been shown to help protect cells from DNA damage and prevent the growth of cancer cells. However, these benefits have not been studied in humans (28).
Similarly, a test-tube test of mustard leaf extract found protective effects against colon and lung cancer. However, human studies are needed (29).
As for human research, observational studies have shown a link between total intake of Brassica vegetables—but not bitter greens—and a reduced risk of certain types of cancer, including stomach, colorectal, and ovarian cancer (30, 31, 32, 33).
How to prepare and eat mustard greens
There are many ways to enjoy mustards.
Raw mustard greens are often added to other mixed greens to give salads a peppery, spicy flavor boost. Some even enjoy using them in smoothies and green juices.
While boiled mustard greens make a delicious side dish to serve with roasted chicken or baked fish, they also work well in soups, stews, and casseroles.
To balance their sharp flavor, these spicy greens are often cooked with fatty sources, such as olive oil or butter, as well as acidic liquids, such as vinegar or lemon juice.
You can pickle mustard greens using a mixture of sugar, salt, vinegar, chili and garlic.
Regardless of how you use them, mustard greens are best stored in the refrigerator and then washed immediately before use.
Potential disadvantages
Although research is limited, mustard is generally considered very healthy and safe. However, they can cause side effects in some people.
As mustard greens are rich in vitamin K – a vitamin that helps blood clot – eating them could interfere with blood-aging drugs.
Therefore, individuals taking blood thinners such as warfarin should consult their physician before incorporating large amounts of these leafy greens into their diet (34).
In addition, mustard greens contain oxalates, which may increase the risk of kidney stones in some individuals if consumed in large amounts. If you are prone to oxalate kidney stones, you may want to limit bitter greens in your diet (35).
Bottom line
Mustard greens represent the pepper leaves of the mustard plant and are incredibly nutritious.
They are particularly rich in vitamin K, vitamin C and plant compounds that can have antioxidant and anticarcinogenic effects. In addition, including mustard in your diet can be beneficial for heart, eye and immune health.
With its peppery, spicy taste, mustard greens are a delicious addition to salads, soups or porridges. They can also be steamed and brushed with olive oil, garlic and lemon juice for a simple side dish.