What is sea cucumbers (Holothuroidea)?
Sea cucumbers, known scientifically as Holothuroidea, are sea creatures found in the Echinodermata phylum. They have a cylindrical body similar to a cucumber, with a tough skin and a single, branched gonad inside. These creatures live on the ocean floor worldwide, from shallow waters to deep sea depths. Sea cucumbers are vital for marine ecosystems as they help recycle nutrients and break down detritus and organic matter, aiding bacterial decomposition. They have a microscopic ossicle or calcareous plates endoskeleton beneath their skin. Many sea cucumber species are harvested for human consumption, with the dried body wall considered a prized delicacy in Asian cuisine, known as trepang, namako, bêche-de-mer, or balate.
Body parts of Sea cucumber (Holothuroidea)
Sea cucumbers have several distinct body parts that enable their unique form and functions. Here is a list of their key body parts with a brief description of each:
- Elongated cylindrical body: Sea cucumbers have a soft, elongated cylindrical body shape resembling a cucumber, ranging from a few centimeters to over 3 meters in length. This allows them to burrow into sediments and move along the seafloor.
- Leathery skin: Their body is covered by a tough, leathery skin containing microscopic ossicles or calcareous plates that form an endoskeleton just below the surface. This provides structural support and protection.
- Tentacles: Sea cucumbers have 10 or more tentacles surrounding their mouth used for feeding by capturing small aquatic animals, detritus, and nutrients from the water or sediment. The number of tentacles varies from 8 to 30 depending on the order.
- Tube feet: Most species have five rows of small tubular appendages called tube feet extending along their body from mouth to anus. These are used for locomotion by gripping surfaces, as well as feeding by sifting through sediments.
- Anus: The anus serves a dual purpose – expelling waste and also respiration by acting as the opening for unique “respiratory trees” that function like lungs. Some species can even expel their internal organs through the anus as a defense mechanism.
- Complete digestive system: Sea cucumbers have a complete digestive tract with a mouth at one end for ingesting food and an anus at the other end for expelling waste, unlike other echinoderms.
Nutritional Profile of Sea cucumber (Holothuroidea)
Sea cucumbers, belonging to the class Holothuroidea, are marine invertebrates known for their high nutritional value and potential health benefits. Below is a detailed summary of the nutritional profile of various sea cucumber species based on multiple research studies.
Protein Content
Sea cucumbers are rich in protein, making them a valuable food source. For instance, Holothuria scabra has a protein content of approximately 47% and 41% for two different species from Madagascar. Similarly, Holothuria arguinensis also exhibits high protein levels. Actinopyga mauritiana and Holothuria arenicola have protein contents of around 67% and 45%, respectively.
Fat Content
The fat content in sea cucumbers is generally low. For example, Holothuria scabra has a lipid content of 1.55% in the whole body and 1.02% in the body wall. Holothuria arguinensis also has low total lipid levels but is rich in polyunsaturated fatty acids (PUFA). The lipid content in Actinopyga mauritiana and Holothuria arenicola is 0.88% and 0.76%, respectively.
Amino Acid Profile
Glycine is the dominant amino acid found in most sea cucumber species. For instance, glycine content ranges from 126 to 216 mg/g of crude protein in various species. Holothuria scabra also contains high levels of glycine, glutamic acid, and proline. The amino acid profile of Holothuria arguinensis is dominated by alanine, glycine, and proline.
Fatty Acid Profile
Sea cucumbers are rich in essential fatty acids. Arachidonic acid (C20:4n-6) is a major PUFA found in many species. Holothuria scabra contains significant amounts of stearic acid and nervonic acid in the whole body, and arachidonic acid and stearic acid in the body wall. The fatty acid profile of Holothuria forskali includes palmitic acid, stearic acid, eicosapentaenoic acid, and arachidonic acid.
Mineral and Vitamin Content
Sea cucumbers are also rich in minerals and vitamins. Holothuria scabra from different locations in Indonesia showed high calcium content and the presence of vitamins B2 and E. Holothuria arguinensis has high levels of calcium
Antioxidant Potential
Several species of sea cucumbers exhibit antioxidant properties. Holothuria arguinensis shows the ability to scavenge free radicals and chelate copper and iron ions. Holothuria tubulosa also demonstrates high antioxidant activities.
Health benefits of Sea cucumber (Holothuroidea)
Sea cucumbers (Holothuroidea) offer numerous potential health benefits due to their nutritional composition. Here are some key health benefits:
1. Reduce inflammation
Sea cucumbers have proven to have strong anti-inflammatory properties, which are beneficial for reducing inflammation. The active components found in sea cucumbers, like scabraside and holothurinoside G, exhibit potent effects against nitric oxide (NO) radicals and form stable connections with KEAP1 and iNOS proteins, important in inflammatory processes. Fucoidan from Holothuria tubulosa can reduce the production of inflammatory cytokines and support the M2 phenotypic polarization of macrophages, aiding in decreasing metabolic inflammation. Research has shown that the methanolic extract of Holothuria atra can significantly lessen paw thickness in rats in a dose-dependent manner, indicating anti-inflammatory effects. Moreover, the ethyl acetate fraction of Holothuria scabra can hinder the release of pro-inflammatory cytokines and nitric oxide through the NF-κB and JNK pathways, suggesting its potential as a natural anti-inflammatory remedy. These discoveries highlight the promising role of sea cucumbers as a source of bioactive compounds for developing anti-inflammatory treatments.
2. Prevents Cancer
Sea cucumbers are rich in bioactive compounds that show promise in preventing and treating cancer. The methanolic extract from Holothuria scabra’s body wall can trigger cell death and inhibit cancer spread in prostate cancer cells by controlling the MAPK signaling pathway. It also reduces cell viability and stops invasion by decreasing MMP-2/-9 expression.
Extracts from Holothuria edulis and Stichopus horrens have potent antioxidant and cytotoxic effects on lung and esophageal cancer cells, hinting at their potential in cancer treatment. Bioactive compounds in sea cucumbers like triterpene glycosides, saponins, and frondoside A have been studied for their anti-inflammatory, immune-boosting, and anti-tumor properties, showing promise in preventing colon cancer in animal models.
Moreover, Holothuria parva extracts can kill breast cancer cells, showcasing sea cucumbers as a potential source of anticancer agents. The various ways sea cucumbers work, like inducing cell death, antioxidative actions, and effects on cell membranes, highlight their therapeutic potential in cancer prevention and treatment.
3. Promote wound healing
Sea cucumbers have shown great potential in helping wounds heal in different ways. The protein from Stichopus japonicus boosts the healing process by activating the PI3K/AKT/mTOR pathway, which speeds up cell movement and growth, leading to more collagen and thicker skin. The hydroalcoholic extract from Holothuria parva speeds up wound closure and encourages the growth of new tissue and skin cells in rats. The gold sea cucumber, Stichopus hermanii, aids in healing by increasing collagen type I production, essential for tissue repair, and reducing ulcer size. Moreover, Actinopyga mauritiana extract, when turned into creams, gels, and serums, has shown promising results in reducing wound size and increasing collagen density in mice. These discoveries highlight the potential of sea cucumbers in healing wounds and suggest they could be valuable for new medical treatments.
4. Treat neurodegenerative diseases
Sea cucumbers have displayed exciting potential in treating neurodegenerative conditions, especially Parkinson’s disease. Substances obtained from Holothuria leucospilota, like palmitic acid, have shown notable protective effects on the nervous system in Caenorhabditis elegans models of PD. These substances help in preserving the health of dopaminergic neurons, enhancing dopamine-related behaviors, lowering oxidative stress, and reducing α-synuclein build-up, all crucial elements in PD. Similarly, diterpene glycosides from Holothuria scabra have been revealed to lessen α-synuclein accumulation and shield dopaminergic neurons from α-synuclein harm, thereby alleviating deficits in dopamine-related behaviors. The healing characteristics of sea cucumbers are linked to their diverse range of bioactive compounds, such as triterpene glycosides, chondroitin sulfates, and glycosaminoglycans, which showcase various beneficial properties like antioxidant, anti-inflammatory, and neuroprotective effects. These discoveries propose that compounds derived from sea cucumbers could be beneficial in producing nutritional therapies and functional foods to help manage neurodegenerative conditions like Parkinson’s disease.
5. Reduce the risk of heart disease
Sea cucumbers have been found to provide potential benefits in reducing the risk of heart disease. Studies on rodents have shown that consuming sea cucumber extracts can help lower cholesterol levels and blood pressure, which are major risk factors for cardiovascular diseases. This cardioprotective effect is attributed to the presence of bioactive compounds like triterpene glycosides, glycosaminoglycans, and fatty acids in sea cucumbers. Specifically, the fatty acid 12-methyltetradecanoic acid found in sea cucumbers may inhibit the proliferation of cells involved in atherosclerosis, the buildup of plaque in arteries that can lead to heart attacks and strokes. Additionally, sea cucumbers are an excellent source of EPA, a type of omega-3 polyunsaturated fatty acid associated with decreased risk of coronary heart disease. Their high protein and low-fat content also make them a heart-healthy food choice.
6. Prevent blood clots
Sea cucumbers offer promising benefits in preventing blood clots or thrombosis. According to a study in the Journal of Thrombosis and Haemostasis, sulfated polysaccharides derived from sea cucumbers have strong anticoagulant and antithrombotic properties. These active compounds can block key enzymes and factors in the blood clotting process, stopping clots from forming. Specifically, fucosylated chondroitin sulfates found in sea cucumbers show significant anticoagulant effects by stopping thrombin and factor Xa, important players in blood coagulation. Moreover, sulfated fucans and fucoidans in sea cucumbers might help prevent clotting by inhibiting platelet aggregation, a crucial step in clot formation. These natural compounds have the potential to become new antithrombotic treatments for preventing and managing conditions like deep vein thrombosis and pulmonary embolism.
7. Manage blood pressure levels
Sea cucumbers have shown promise in helping to regulate blood pressure levels. Research on rodents has revealed that consuming sea cucumber extracts can assist in lowering high blood pressure or hypertension. This blood pressure-lowering effect is due to the presence of bioactive compounds such as triterpene glycosides, glycosaminoglycans, and peptides in sea cucumbers. Particularly, the peptides obtained from sea cucumber collagen have displayed angiotensin-converting enzyme (ACE) inhibitory properties, which can aid in relaxing blood vessels and reducing blood pressure. Moreover, the high potassium and low sodium levels in sea cucumbers might also play a role in reducing blood pressure by encouraging sodium excretion and vasodilation. Interestingly, a study discovered that a diet incorporating 5% dried sea cucumber was effective in decreasing both systolic and diastolic blood pressure in hypertensive rats.
How to incorporate Sea cucumber (Holothuroidea) in your diet
Here are some ways to incorporate sea cucumbers (Holothuroidea) into your diet:
- Add rehydrated dried sea cucumber to soups, stews, and stir-fries.
- Enjoy fresh sea cucumber in sashimi or lightly cooked dishes to appreciate its natural flavor.
- Braise or stew sea cucumbers for an extended time to allow them to absorb flavors from ingredients like mushrooms, bamboo shoots, and sauces.
- Boil or simmer sea cucumbers until tender before adding to dishes.
- Stir-fry sea cucumbers with vegetables like cabbage, winter melon, and strong spices to infuse flavor.
- Combine sea cucumbers with protein-rich ingredients like seafood, tofu, or meat.
- Pair with umami-rich sauces and seasonings like soy sauce, oyster sauce, and abalone sauce.
- Incorporate sea cucumbers into Asian cuisines like Chinese, Japanese, Korean, and Indonesian dishes.
Potential Side Effects and Precautions
Sea cucumbers are generally safe to eat, with few known side effects. However, it’s essential to take some precautions. If you have seafood allergies, it’s best to steer clear of sea cucumbers as they could cause an allergic reaction. There’s a risk of toxicity if sea cucumbers come from polluted waters with heavy metals. It’s crucial to clean and prepare them properly to get rid of any potential toxins. Sea cucumbers might also interfere with certain medications, so it’s wise to talk to a healthcare provider before eating them, especially if you have existing health issues. Pregnant or nursing women should be careful since there’s limited safety information. Overall, when sourced from clean waters and prepared well, sea cucumbers are usually well-tolerated. Still, it’s important to be cautious, especially for specific groups of people.