Editor’s Note: Each month, HerbalEGram highlights a conventional food and
briefly explores its history, traditional uses, nutritional profile, and modern
medicinal research. We also feature a nutritious recipe for an easy-to-prepare
dish with each article to encourage readers to experience the extensive
benefits of these whole foods. With this series, we hope our readers will gain
a new appreciation for the foods they see at the supermarket and frequently
include in their diets.
The basic materials for this
series were compiled by dietetic interns from Texas State University (TSU) in
San Marcos and the University of Texas at Austin (UT) through the American
Botanical Council’s (ABC’s) Dietetic Internship Program, led by ABC Education
Coordinator Jenny Perez.
We would like to acknowledge Jenny Perez, ABC Special Projects Director Gayle
Engels, and ABC Chief Science Officer Stefan Gafner, PhD, for their
contributions to this project.
By Hannah Baumana and Melanie Leslieb
a HerbalGram Associate Editor b ABC Dietetics Intern (TSU, 2015)
Overview
Rutabaga
(Brassica napus subsp. rapifera, Brassicaceae), also known as
“swede” or “Swedish turnip,” is a natural hybrid between cabbage (B. oleracea) and turnip (B. rapa).1 It can also be
found under the subspecies “napobrassica.”
Considered a root vegetable, the rutabaga is actually the enlarged base of the
stem of the plant.2 Most commonly, rutabagas have a pale yellow or
white inner flesh and a darker yellow or purple exterior.
Rutabaga
is a relative newcomer to the world of domesticated crops, with its first mention
in botanical literature appearing in the 17th century.3 The nickname
“swede” comes from the plant’s geographical origin, as it became a fixture in
Swedish agriculture before spreading around the world.4 It was
introduced in North America in the early 19th century.
A
biennial plant that stores well, rutabaga thrives in cooler climates where the
summer season is not excessively hot.5 Rutabagas are considered a
root crop, and lend themselves to longer post-harvest storage when placed in a
root cellar or similar environment that is damp and cool, lasting up to six
months in storage.6,7 To prevent loss of moisture during storage or
transit, the green tops are removed and the bulbs are waxed.5
Phytochemicals and Constituents
Rutabagas
are rich in carbohydrates and fiber and contain little fat or protein.8
They contain about half of the calorie content of potatoes, and are relatively high
in vitamin C and potassium.
A
diet high in fiber has many benefits, primarily for the gastrointestinal tract.9
Insoluble fiber, which cannot be absorbed and digested, promotes healthy bowel
movements and lowers the risk of developing disorders such as acid reflux,
ulcers, constipation, hemorrhoids, and diverticulosis, a condition in which
small, bulging pouches develop along the digestive tract. These pouches can
become inflamed, which is known as diverticulitis, causing abdominal pain and
fever and requiring treatment. The fiber content of rutabagas consists mostly
of insoluble fiber, which, in addition to maintaining bowel health, may also
lower the risk of cardiovascular disease, hypertension, diabetes, stroke, and
obesity.10
Potassium
is an essential mineral for the body. It functions as an electrolyte,
conducting electricity through the body, ensuring the proper function of cells,
tissues, and organs.11 Other important electrolytes include sodium,
chloride, calcium, and magnesium. Maintaining healthy potassium levels is vital
for maintaining bone health, especially for the aging population, and people
with diets high in potassium are at lower risk for stroke and heart disease.
Additionally, potassium levels depend on an inverse relationship with salt
intake: those who consume too much sodium in proportion to potassium will have
less potassium available for absorption by the body.12
Other
bioactive components in rutabagas include glucosinolates and phenols, similar
to other plants in the Brassicaceae family, such as broccoli
(Brassica oleracea)13.
Glucosinolates are precursors to isothiocyanates, which may reduce the risk of
certain cancers.14 In the
plant, glucosinolates are converted to isothiocyanates by an enzyme called
myrosinase. However, the enzyme is deactivated with excessive heat, so cooking
rutabaga will impact the conversion of glucosinolates to isothiocyanates. Gut
bacteria also have this ability to convert glucosinolates to isothiocyanates.
Phenols act as antioxidants, which reduce free radicals in the body.
Historical and Commercial Uses
The
cultivation of rutabagas began in the 1600s in Bohemia (which now makes up the western
Czech Republic) before they made their way to Scandinavia, where the
cold-weather crop was embraced as both food for humans and livestock.6
By the 18th century, rutabaga consumption had spread to France and England.2
Rutabagas were introduced in the United States in the early 19th century, where
they were primarily grown as livestock fodder. Because the plant is so hardy
and grows well in bad weather conditions, rutabagas became associated with
times of scarcity, which impacted their popularity as a food product. Even in
modern times in the United States, they are not as widely consumed as other,
more familiar root vegetables. However, the rutabaga has had some interesting
cultural impacts.
Jack
o’ lanterns are a Halloween tradition with roots in Irish culture. The origin
myth tells the story of a trickster named Jack, who thwarted the devil’s plan
to take his soul and found his way out of hell with the aid of a burning ember
and a hollowed-out rutabaga (or “turnip”).15 Though the rutabaga’s
colloquial name of “turnip” in the British Isles has resulted in the erroneous
belief that Brassica rapa was used,
it is accepted by the standard lore that rutabagas were, in fact, the first
jack o’ lanterns. When the practice migrated to the United States, where
pumpkins (Cucurbita pepo,
Cucurbitaceae) were readily available and already involved in many fall
celebrations, the pumpkin replaced the rutabaga.
Many
towns with a prominent Scandinavian population have events to celebrate the
rutabaga and its place in cultural traditions. One of the more tongue-in-cheek
celebrations is the International Rutabaga Curl competition, which has been a
tradition in Ithaca, New York, since 1996.16 Notably, in 2016, the town of Cumberland, Wisconsin, held its 84th Annual Rutabaga Festival Parade.
Modern Research
In
a recent study, rutabaga methanol extracts killed human liver cancer cells in
vitro and also decreased the rate of
cancer cell proliferation.17 The normal, non-cancerous cells were
not affected. Compared to root or seed extracts, rutabaga sprout extracts were
more effective at battling liver cancer cells. This was due to the
significantly higher levels of flavonoids found in the rutabaga sprout, which
correlated to stronger antioxidant activity.
Rutabaga
is a variety of the rapeseed plant (Brassica
napus, Brassicaceae). Brassica napus contains
plant sterols that, in isolation, have shown effects against prostate cancer
cells.18 The sterol called brassinolide induced apoptosis (normal, pre-programmed
cell death) in these prostate cancer cells during in vitro trials. Researchers
concluded that brassinolide “might therefore be a promising candidate for the
treatment of prostate cancer.”
The
bioactive compounds present in cruciferous vegetables, including rutabagas,
have been studied for many different conditions. A randomized, crossover,
controlled study showed that intestinal bacteria were changed within two weeks
of eating a diet rich in cruciferous vegetables, although the bacterial colonization
was different with each study participant.19 A hospital-based,
case-control study showed that consumption of raw, rather than cooked,
cruciferous vegetables decreased risk of bladder cancer.20 Additionally,
growth conditions can impact the glucosinolate content in cruciferous
vegetables.21 Supplementing the soil with selenium, nitrogen, or
sulfur was correlated with an increase in glucosinolate content, but when
applied in excess had an inhibiting effect.
Rutabaga’s
status as a nutritious food has often been overlooked in the United States.
Combined with its ease of preparation and possible health benefits, this
less-glamorous cousin of cabbage and turnips deserves a popularity renaissance.
Nutrient Profile8
Macronutrient Profile: (Per 1 cup raw
rutabaga cubes [approx. 140 g])
52 calories 1.5 g
protein 12.07
g carbohydrate 0.22
g fat
Secondary Metabolites: (Per 1 cup raw
rutabaga cubes [approx. 140 g])
Excellent source of: Vitamin
C: 35 mg (58.3% DV)
Very good source of: Potassium:
427 mg (12.2% DV) Dietary
Fiber: 3.2 g (12.8% DV)
Good source of: Manganese:
0.18 mg (9.2% DV) Thiamin:
0.13 mg (8.7% DV) Phosphorus:
74 mg (7.4% DV) Folate:
29 mcg (7.3%DV) Magnesium:
28 mg (7.0% DV) Vitamin
B6: 0.14 mg (7.0% DV) Calcium:
60 mg (6.0% DV)
Also provides: Niacin:
0.98 mg (4.9% DV) Riboflavin:
0.06 mg (3.5% DV) Iron:
0.62 mg (3.4% DV) Vitamin
E: 0.42 mg (1.4% DV)
DV =
Daily Value as established by the US Food and Drug Administration, based on a
2,000-calorie diet.
Recipe: Honey-Lemon
Glazed Rutabagas and Carrots
Adapted from: Bon Appétit22
Ingredients:
- 1 1/4
pounds rutabaga, peeled and sliced into matchstick-sized strips
- 1
pound carrots, peeled and sliced into matchstick-sized strips
- 1/4
cup unsalted butter
- 1/4
cup freshly-squeezed lemon juice
- 1
teaspoon grated lemon zest
- 3
tablespoons honey
- 1/2
cup fresh chives, minced
- Salt
and pepper to taste
Directions:
- In a
large saucepan, bring lightly salted water to boil. Add rutabagas and cook for
2 minutes. Add carrots and cook until vegetables are tender, about 3 minutes.
Drain.
- Melt
butter in a large saucepan over medium-high heat. Add lemon juice, zest, and
honey. Bring to a boil.
- Add
the vegetables and cook until glazed, stirring occasionally, about 6 minutes.
Season to taste with salt and pepper.
- Remove
from heat and stir in chives.
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