What is Kohlrabi ?
Kohlrabi, a member of the Cruciferae (Brassicaceae) family, is a biennial, herbaceous vegetable crop typically grown as an annual for its swollen, bulb-like stem, which develops above the ground due to secondary growth in thickness. This vegetable is cultivated in temperate and some subtropical regions and is known for its nutritional and health benefits, including high levels of vitamin C, potassium, and antioxidant substances. There are two main cultivars of kohlrabi: pale green and purple, which differ in their metabolic profiles and phenolic compound accumulation. The purple variety is particularly noted for its high anthocyanin content, which contributes to its color and potential health benefits. Kohlrabi is also susceptible to several diseases, including Fusarium wilt and clubroot, which can affect its cultivation. Additionally, kohlrabi extract has shown potential in enhancing cell viability and reducing apoptosis in mesenchymal stem cells, indicating its possible therapeutic applications. The plant’s growth and yield can be significantly influenced by factors such as seedling age, NPK fertilization, and light conditions, with specific light-emitting diode (LED) lights enhancing the accumulation of beneficial metabolites.
Nutritional Profile of Kohlrabi
Kohlrabi, also known as the German turnip, is a nutrient-dense vegetable that belongs to the cruciferous family. It is low in calories yet packed with essential vitamins, minerals, and antioxidants. A single cup (135 grams) of raw kohlrabi provides around 36 calories, making it an excellent choice for those looking to manage their weight while still obtaining vital nutrients.
Macronutrients
Carbohydrates
Kohlrabi contains approximately 8 grams of carbohydrates per cup, with 4 grams coming from natural sugars and 5 grams from dietary fiber. The high fiber content supports digestive health by promoting regular bowel movements and maintaining healthy blood sugar levels.
Proteins
Although not a significant source of protein, kohlrabi still offers about 2 grams per cup. This modest amount contributes to the overall protein intake, especially when combined with other protein-rich foods in a balanced diet.
Fats
Kohlrabi is virtually fat-free, containing only 0.1 grams of fat per cup. This makes it an ideal addition to low-fat diets and a heart-healthy choice for individuals looking to reduce their fat intake.
Micronutrients
Vitamins
Kohlrabi is particularly rich in vitamin C, providing 93% of the daily value per cup. This powerful antioxidant plays a crucial role in immune function, collagen synthesis, and the protection against free radical damage. Additionally, kohlrabi is a good source of vitamin B6, which supports protein metabolism, red blood cell production, and immune health.
Minerals
Among the essential minerals found in kohlrabi, potassium stands out, with one cup offering 10% of the daily value. Potassium is vital for maintaining fluid balance, nerve function, and muscle contractions. Kohlrabi also contains magnesium, contributing 6% of the daily value per cup, which is important for bone health, muscle function, and energy production.
Types of Kohlrabi
Here are individual paragraphs on some notable kohlrabi varieties:
1. Early White Vienna
Early White Vienna is a classic heirloom variety known for its quick maturity and excellent flavor. This pale green kohlrabi reaches harvest size in about 55-60 days, producing flattened globes 2-3 inches in diameter. It has a mild, sweet taste and tender texture, making it ideal for both raw and cooked applications. Early White Vienna is prized for its compact growth habit and resistance to bolting, allowing for extended harvests in cooler weather.
2. Purple Vienna
Purple Vienna is a striking variety that adds visual appeal to gardens and plates alike. Its vibrant purple skin contrasts beautifully with the crisp white flesh inside. Maturing in approximately 60 days, Purple Vienna produces slightly flattened bulbs about 2-3 inches across. This variety is known for its sweet, mild flavor and tender texture. The purple coloration is superficial, limited to the skin, while the interior remains white. Purple Vienna is also noted for its potential resistance to certain pests, making it a favorite among organic gardeners.
3. Kossak
Kossak is a giant storage variety that stands out for its impressive size and long-lasting quality. This green kohlrabi can grow up to 8 inches in diameter while maintaining its sweet, tender flavor – a trait uncommon in larger kohlrabi varieties. Ready for harvest in about 70 days, Kossak is prized for its ability to store for up to 4 months when kept in cool conditions. This makes it an excellent choice for gardeners looking to extend their kohlrabi season well into winter. Despite its large size, Kossak remains crisp and flavorful, avoiding the woodiness often associated with oversized kohlrabi.
4. Azur Star
Azur Star is a fast-maturing, purple variety that adds both color and flavor to the garden. Ready for harvest in just 50 days, it produces uniform, slightly flattened bulbs with a striking blue-purple exterior. The interior flesh is crisp and white, offering a sweet and mild flavor. Azur Star is known for its slow-bolting characteristic, making it a good choice for spring planting. Its attractive appearance and excellent taste make it popular for both market growers and home gardeners. The leaves are also edible and can be used like other brassica greens.
Science backed health benefits of Kohlrabi
Kohlrabi, often overshadowed by its more popular cruciferous cousins like broccoli and kale, is a nutritional powerhouse with a wealth of health benefits supported by scientific research. This versatile vegetable is packed with essential vitamins, minerals, and antioxidants that can positively impact your health in numerous ways. From boosting your immune system and enhancing digestion to supporting heart health and potentially reducing cancer risk, kohlrabi offers a range of advantages that make it a worthy addition to your diet. In this article, we’ll explore the science-backed health benefits of kohlrabi and why you should consider incorporating it into your meals.
1. Manage inflammatory conditions
Kohlrabi is a cruciferous vegetable known for its potent anti-inflammatory properties, largely attributed to its rich content of antioxidants such as vitamin C, isothiocyanates, and glucosinolates. These compounds help neutralize free radicals, which are unstable molecules that can cause cellular damage and inflammation. Vitamin C, in particular, plays a crucial role in reducing inflammation by fighting off infections and boosting the immune system. Additionally, kohlrabi’s high phenolic content, especially in its red variety, has been shown to exhibit significant anti-inflammatory effects by inhibiting the production of inflammatory proteins like iNOS and COX-2. Regular consumption of kohlrabi can thus contribute to managing and potentially reducing the risk of chronic inflammatory conditions such as cardiovascular disease and diabetes.
What Research Says?
- Both green and red kohlrabi cultivars exhibit significant anti-inflammatory activities. Methanol extracts from these cultivars inhibit lipopolysaccharide (LPS)-induced nitric oxide (NO) production in a dose-dependent manner, which is further supported by the suppression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein production.
- Kohlrabi contains plant lectins, which are proteins known for their cell agglutination properties. These lectins have potential anti-inflammatory, anti-diabetic, and antioxidant properties, although their specific anti-inflammatory mechanisms need further investigation.
2. Beneficial for cancer treatment
Kohlrabi holds promise in cancer treatment due to its abundance of bioactive compounds, particularly glucosinolates and isothiocyanates, which have been extensively studied for their anti-carcinogenic properties. When consumed, glucosinolates are broken down into isothiocyanates, which have been shown to inhibit the growth of cancer cells and induce apoptosis, or programmed cell death, in various cancer types. Additionally, kohlrabi is rich in antioxidants like vitamin C and flavonoids, which help protect cells from oxidative stress and DNA damage, both of which are critical factors in cancer development. The vegetable’s high fiber content also supports detoxification processes, aiding in the removal of potential carcinogens from the body. Regular inclusion of kohlrabi in the diet may thus contribute to cancer prevention and complement conventional cancer therapies by enhancing the body’s natural defense mechanisms.
What Research Says?
- Brassica oleracea var. gongylodes biomass can be used to synthesize reduced graphene oxide (rGO) and gold nanoparticles (Au NPs) nanocomposites. These nanocomposites exhibit significant photothermal properties, leading to the destruction of MCF7 breast cancer cells when exposed to near-infrared light.
- Various Brassica oleracea varieties, including kohlrabi, have been shown to possess cancer-preventive properties. This is supported by both experimental testing of crude extracts and epidemiological data, which suggest that specific chemicals in these plants contribute to their anticancer effects.
- Lectins extracted from Brassica oleracea var. gongylodes have shown potential anticancer effects. These proteins can agglutinate cells and inhibit cell growth, making them promising for further research in cancer detection and therapy.
- Different parts of Brassica oleracea var. gongylodes, such as leaves, flesh, and peel, contain high levels of antioxidants and other beneficial compounds. These biochemicals can fend off cancer, diabetes, and high cholesterol, highlighting the plant’s potential as a nutraceutical and functional food.
- Ethyl acetate extracts of Brassica oleracea have been found to inhibit the growth of hepatocellular carcinoma cells. These extracts exert cytostatic effects, trigger apoptosis, and induce necrosis, making them promising for developing new anticancer therapies.
3. Improved metabolic functions
Kohlrabi can significantly improve metabolic functions due to its rich nutrient profile, particularly its high content of vitamin B6 and fiber. Vitamin B6 plays a crucial role in protein metabolism and the development of red blood cells, which are essential for maintaining efficient metabolic processes. Additionally, kohlrabi’s fiber content aids in regulating blood sugar levels and promotes a healthy gut microbiome, both of which are critical for optimal metabolic health. The vegetable’s antioxidants, including vitamin C and glucosinolates, further support metabolic functions by reducing oxidative stress and inflammation, which can otherwise impair metabolic efficiency. Regular consumption of kohlrabi can thus help enhance overall metabolic health and prevent metabolic disorders.
What Research Says?
- Purple kohlrabi contains higher levels of anthocyanins, particularly cyanidin, compared to pale green kohlrabi, which lacks anthocyanins.
4. Help in reducing oxidative stress
Kohlrabi is highly effective in reducing oxidative stress due to its rich content of antioxidants, particularly vitamin C, glucosinolates, and carotenoids. These antioxidants play a crucial role in neutralizing free radicals, which are unstable molecules that cause cellular damage and contribute to oxidative stress. By scavenging these free radicals, kohlrabi helps protect cells from oxidative damage, thereby lowering the risk of chronic diseases such as cancer, cardiovascular disease, and diabetes. Additionally, the high phenolic content in kohlrabi, especially in its red variety, further enhances its antioxidant capacity, making it a valuable addition to a diet aimed at reducing oxidative stress and promoting overall health.
What Research Says?
- Selenium (Se) supplementation in Brassica oleracea significantly enhances the plant’s antioxidant defense mechanisms under arsenic (As) stress. This includes increased activities of enzymatic antioxidants like peroxidase (POD) and glutathione reductase (GR), as well as non-enzymatic antioxidants such as anthocyanins and total flavonoids. These improvements help in reducing oxidative damage and improving plant growth and physiological performance under stress conditions.
5. Protect the body against fungal infections
Kohlrabi exhibits significant antifungal properties that help protect the body against fungal infections. The seeds of kohlrabi contain an antifungal peptide known as BGAP, which has been shown to inhibit the growth of various fungal pathogens, including Colletotrichum higginsianum, Exserohilum turcicum, and Mycosphaerella arachidicola. This peptide works by increasing cell membrane permeability, generating reactive oxygen species (ROS), and causing chitin accumulation at the hyphal tips of fungi, which disrupts their cellular integrity and function. Additionally, kohlrabi’s bioactive compounds, such as isothiocyanates, have been reported to exhibit broad-spectrum antimicrobial activity, further enhancing its protective effects against fungal infections. Regular consumption of kohlrabi can thus contribute to the body’s defense mechanisms against fungal pathogens.
What Research Says?
- Kohlrabi can form localized wall appositions in response to mechanical wounding, which effectively prevent fungal penetration at the wound sites.
- Kohlrabi leaves contain various phenolic compounds and flavonoids, which are known for their antioxidant and antibacterial properties. These compounds may also contribute to antifungal activities, although the specific antifungal effects were not directly studied.
6. Regulate blood sugar levels
Kohlrabi can help regulate blood sugar levels, making it a beneficial addition to the diet of individuals managing diabetes or prediabetes. This cruciferous vegetable is rich in dietary fiber, which slows down the digestion and absorption of carbohydrates, preventing rapid spikes in blood sugar levels. Its low glycemic index further ensures a gradual release of glucose into the bloodstream, promoting stable energy levels and glycemic control. Additionally, kohlrabi contains bioactive compounds such as glucosinolates and isothiocyanates, which have been shown to improve insulin sensitivity and reduce insulin resistance, key factors in managing blood sugar levels effectively. Regular consumption of kohlrabi can thus support better blood sugar management and overall metabolic health.
What Research Says?
- Administration of phenolic-rich extracts from Brassica oleracea var. gongylodes significantly reduced fasting blood glucose levels in diabetic rats by 64% within 7 days.
- Aqueous extracts of Brassica oleracea var. viridis significantly lowered blood glucose levels in streptozotocin-induced diabetic rats, achieving normal values after repeated administration.
- High antioxidant activities were observed in the leaves of Brassica oleracea var. gongylodes, attributed to the presence of phenolic compounds like chlorogenic acid and epigallocatechin.
7. Reduces bad cholesterol levels
Kohlrabi has shown promising potential in reducing bad cholesterol levels, primarily due to its high fiber content and unique phytochemical profile. The soluble fiber found in kohlrabi plays a crucial role in lowering low-density lipoprotein (LDL) cholesterol, often referred to as “bad” cholesterol. This fiber binds to dietary cholesterol in the small intestine, preventing its absorption into the bloodstream and facilitating its elimination from the body. Additionally, kohlrabi contains glucosinolates and isothiocyanates, plant compounds that have been associated with improved heart health and cholesterol management. Close relative of kohlrabi in the Brassica family, substantially reduced total cholesterol and low-density lipoprotein levels.
What Research Says?
- Brassica oleracea var. gongylodes is rich in biochemicals that can fend off high cholesterol, among other health benefits.
- A study on a mixed green vegetable and fruit beverage containing other Brassica oleracea varieties (broccoli and cabbage) showed a significant reduction in low-density lipoprotein cholesterol (LDL-C) levels in hypercholesterolemic patients.
Incorporating Kohlrabi into Your Diet
Kohlrabi, a cruciferous vegetable related to cabbage, broccoli, and Brussels sprouts, is a nutritional powerhouse that offers numerous health benefits. It’s rich in vitamins C and B6, fiber, and antioxidants, which support immune health, digestion, and reduce inflammation. Incorporating kohlrabi into your diet can be a delightful way to enhance your meals with its unique flavor, which is often described as a cross between a cucumber and a broccoli stem. Whether you enjoy it raw, cooked, or in soups and stews, kohlrabi is a versatile vegetable that can fit into various culinary traditions.
Tips for Preparation and Consumption
Preparing kohlrabi is straightforward and can be done in several ways to suit different tastes and recipes. Start by peeling the tough outer layer using a vegetable peeler or a sharp knife, especially if the bulb is mature. The inner flesh can be sliced, diced, or grated depending on the dish. Kohlrabi can be enjoyed raw in salads or slaws, where its crisp texture adds a refreshing crunch. For a warm dish, try roasting it with olive oil and spices, or steaming it for a tender, mild-flavored side. Kohlrabi can also be puréed into soups, adding a creamy texture without the need for dairy.
How to Choose Fresh Kohlrabi
Selecting fresh kohlrabi is essential for the best flavor and texture. When at the market, look for smaller bulbs, ideally 2-3 inches in diameter, as they tend to be sweeter and less fibrous. The skin should be smooth and free from blemishes or cracks. If the leaves are still attached, they should be vibrant green and not wilted or yellowing, indicating freshness. Avoid bulbs that feel soft or have spongy spots, as these are signs of aging or poor storage.
Tips for Selecting and Storing Kohlrabi
Proper storage is key to maintaining the freshness of kohlrabi. Once you bring it home, cut off the leaves if they are still attached and store them separately in a damp paper towel inside a plastic bag in the refrigerator; they should be used within a few days. The bulbs can be stored in the crisper drawer of your refrigerator, wrapped in plastic or placed in a sealed bag, where they can stay fresh for up to two weeks. For longer storage, peel, blanch, and freeze the bulbs, which can then be kept for up to 10-12 months.
Different Ways to Cook and Enjoy Kohlrabi
Kohlrabi’s versatility in the kitchen makes it a fantastic addition to various dishes. Enjoy it raw by slicing it into sticks for a crunchy snack or grating it into salads for added texture. Steaming kohlrabi softens its texture while retaining its mild flavor, making it a great side dish when tossed with herbs and olive oil. Roasting kohlrabi brings out its natural sweetness; simply dice, season, and bake until caramelized. It also works well in soups and stews, where it can be diced or puréed for a creamy consistency. Additionally, kohlrabi can be sautéed with garlic and onions for a flavorful stir-fry.
Combining with Other Foods for Maximum Benefits
To maximize the nutritional benefits of kohlrabi, combine it with other nutrient-dense foods. Pairing kohlrabi with high-protein ingredients like chicken or legumes can create a balanced meal. Adding it to a salad with leafy greens, nuts, and seeds boosts the fiber and antioxidant content, promoting better digestion and overall health. For a hearty dish, mix kohlrabi with root vegetables like carrots and potatoes in a roast or stew, enhancing the meal’s vitamin and mineral profile. Experimenting with different combinations can help you discover delicious and healthy ways to enjoy kohlrabi regularly.
Side Effects of Eating Kohlrabi
While kohlrabi is generally safe and nutritious, consuming it in large amounts can lead to several side effects. One of the primary issues is gastrointestinal discomfort, including bloating, gas, and diarrhea, due to its high fiber content. This is because fiber takes longer to digest, and overeating can strain the digestive system. Additionally, kohlrabi contains thiocyanates, which can interfere with iodine absorption and potentially affect thyroid function, making it advisable for individuals with thyroid issues to consult their healthcare provider before consuming large quantities. Excessive consumption can also lead to hyperkalemia, a condition caused by high potassium levels, which can affect heart health. Lastly, as with all produce, it’s essential to wash kohlrabi thoroughly to avoid harmful bacteria and parasites. Moderation and proper preparation are key to enjoying kohlrabi without adverse effects.
Conclusion
Kohlrabi emerges as a remarkable vegetable with an impressive array of health benefits, making it a valuable addition to any diet. Rich in essential vitamins, particularly vitamin C and B6, as well as dietary fiber and antioxidants, kohlrabi supports immune function, aids digestion, and helps manage inflammation. Its unique phytochemical profile, including glucosinolates and isothiocyanates, contributes to its potential in cancer prevention, cholesterol reduction, and blood sugar regulation. Moreover, the vegetable’s versatility in culinary applications—from raw salads to cooked dishes—enhances its appeal. Overall, incorporating kohlrabi into daily meals not only promotes better health but also introduces a delicious and nutritious option that can benefit various dietary preferences.
ADDITIONAL RESOURCES
Here’s a list of US organizations involved in research on vegetables, along with their short descriptions and URLs:
1. American Society for Horticultural Science (ASHS)
ASHS is dedicated to advancing the knowledge and practice of horticultural science through education, research, and service activities.
2. University of California Agriculture and Natural Resources (UC ANR)
UC ANR conducts research and extension programs to address challenges in agriculture, including vegetable crop production, pest management, and sustainable farming practices.
The Rodale Institute is a nonprofit organization dedicated to pioneering organic farming through research and outreach, including studies on vegetable crop production.
Recommendations for books on Kohlrabi
Here are some recommendations for books on research related to Kohlrabi, along with links:
1. “Vegetable Brassicas and Related Crucifers” by G. R. Dixon
This book covers a wide range of topics related to brassica vegetables, including kohlrabi. It provides detailed information on the cultivation, genetics, breeding, and pest management of these crops.
2. “Handbook of Vegetables and Vegetable Processing” edited by Nirmal K. Sinha, YiFang Chu, and Wiley J. Lo
This comprehensive book offers extensive coverage of vegetable processing, including kohlrabi. It delves into various aspects such as nutrition, processing methods, and food safety.
3. “Kohlrabi: Improving Production and Postharvest Quality” edited by various experts
This book focuses on the latest research and developments in the cultivation and postharvest handling of kohlrabi. It includes case studies, best practices, and innovative techniques for improving yield and quality.
FAQS
- What are the main nutritional benefits of kohlrabi?
Kohlrabi is an excellent source of vitamin C, providing over 100% of the daily recommended value in just one cup. It’s also rich in fiber, potassium, magnesium, and vitamin B6. Additionally, kohlrabi contains powerful antioxidants such as anthocyanins, isothiocyanates, and glucosinolates.
- How does kohlrabi support heart health?
Kohlrabi supports heart health through its high fiber content, potassium, and antioxidants. These nutrients help lower blood pressure, reduce inflammation, and decrease the risk of heart disease. Studies have shown that diets rich in cruciferous vegetables like kohlrabi are associated with a lower risk of cardiovascular disease.
- Can kohlrabi help in cancer prevention?
Yes, kohlrabi contains compounds that may help fight cancer. Its glucosinolates and isothiocyanates have been shown to stop the growth of cancer cells in various parts of the body, including breast, lung, colon, and cervix. Research indicates that consuming cruciferous vegetables like kohlrabi is associated with a reduced risk of certain cancers.
- How does kohlrabi benefit digestive health?
Kohlrabi is rich in both soluble and insoluble fiber, which promotes digestive health. This fiber helps maintain regular bowel movements, prevents constipation, and supports a healthy gut microbiome. The prebiotic properties of kohlrabi’s fiber also nourish beneficial gut bacteria.
- Can kohlrabi help with weight management and diabetes prevention?
Yes, kohlrabi can aid in weight management and diabetes prevention. Its high fiber and water content can enhance satiety and reduce overall calorie intake. Studies suggest that higher intakes of vegetables like kohlrabi may result in a reduced risk of type 2 diabetes.
- What role does kohlrabi play in immune system support?
Kohlrabi is rich in vitamin C, which is crucial for immune system function. It also contains other antioxidants and compounds that have anti-inflammatory properties, further supporting overall immune health.
- How does kohlrabi contribute to bone health?
Kohlrabi contains calcium and magnesium, both of which are essential for bone health. Regular consumption of kohlrabi, along with other calcium-rich foods and weight-bearing exercise, may help increase bone density.
- Can kohlrabi benefit skin health?
Yes, kohlrabi can benefit skin health. Its high vitamin C content promotes collagen production, which may help reduce visible signs of aging such as wrinkles and fine lines. The hydrating properties of kohlrabi also contribute to skin health.
- How does kohlrabi support brain health?
Kohlrabi supports brain health through its vitamin B6 content, which is crucial for neurotransmitter creation. Additionally, the anthocyanins in kohlrabi are considered neuroprotective agents, potentially safeguarding against neurodegenerative diseases like Alzheimer’s and Parkinson’s.
- Are there any potential side effects or precautions when consuming kohlrabi?
While kohlrabi is generally safe to consume, eating large quantities may cause bloating or gas in some individuals due to its high fiber content. People with gastrointestinal issues should be cautious when consuming raw kohlrabi. As with any dietary change, it’s best to consult with a healthcare professional, especially if you have existing health conditions or are on medication.
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