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Wasabi, beloved on sushi, linked to "really substantial" boost in memory, Japanese study finds
A study conducted in Japan suggests there's more to sushi than just a healthy dose of fish and seaweed. Researchers at Tohoku University found that wasabi, that spicy green condiment traditionally dabbed on the raw fish dish, improves both short- and long-term memory.
Rui Nouchi, the study's lead researcher and an associate professor at the school's Institute of Development, Aging and Cancer, told CBS News the results, while based on a limited sample of subjects without preexisting health conditions, exceeded their expectations.
"We knew from earlier animal studies that wasabi conferred health benefits," he said in an interview from his office in northeast Japan. "But what really surprised us was the dramatic change. The improvement was really substantial."
The main active component of Japanese wasabi is a biochemical called 6-MSITC, a known antioxidant and anti-inflammatory known to exist in only trace amounts elsewhere throughout the plant kingdom, Nouchi said. The double-blind, randomized study involved 72 healthy subjects, aged 60 to 80. Half of them took 100 milligrams of wasabi extract at bedtime, with the rest receiving a placebo.
After three months, the treated group registered "significant" boosts in two aspects of cognition, working (short-term) memory, and the longer-lasting episodic memory, based on standardized assessments for language skills, concentration and ability to carry out simple tasks. No improvement was seen in other areas of cognition, such as inhibitory control (the ability to stay focused), executive function or processing speed.
Subjects who received the wasabi treatment saw their episodic memory scores jump an average of 18%, Nouchi said, and scored on average 14% higher than the placebo group overall.
The researchers theorized that 6-MSITC reduces inflammation and oxidant levels in the hippocampus, the area of the brain responsible for memory function, and boosts neural plasticity.
Compared with the control group, the study said, subjects dosed with wasabi "showed improved verbal episodic memory performance as well as better performance in associating faces and names, which is often the major memory-related problem in older adults."
Wasabi is a member of the mustard family of plants. The fiery condiment paste made with it became prized in Japan centuries ago for its antimicrobial properties, which make it capable of killing off foodborne pathogens such as E-coli and staphylococcus, while its flavor and aroma complemented seafood.
A specialist in dementia prevention, Nouchi landed on wasabi treatment after finding high dropout rates with conventional methods of preserving brain health, such as the Mediterranean diet, exercise and music therapy. A daily supplement, he decided, would be more sustainable, especially for seniors, while offering more benefit than other anti-inflammatory, antioxidant spices such as ginger and turmeric.
The Tohoku University team aims to test wasabi on other age groups and explore whether the spice can slow cognitive decline in dementia patients.
But here's the rub: That tangy paste served up at nearly all sushi bars — even the ones in Japan — is almost certainly an impostor. Far more common than the real thing is a convincing fraud, usually made of ordinary white horseradish, dyed green.
Native to Japan, wasabi is notoriously difficult to cultivate. The plant takes nearly two years to reach maturity and requires exacting temperature, shade, gravel and water conditions. It can cost more per pound than even the choice tuna it sits on.
Genuine wasabi must be consumed fresh, with the stubbly rhizome, or stem of the plant, grated tableside just before eating. On the plus side, just a small dab offers the same benefits as the capsule supplements used in the Tohoku study, or 0.8 milligrams of 6-MSITC.
注释：
condiment: n
表示" 调味品；佐料"，如：Fish sauce is a traditional fermented condiment in coastal areas. 鱼露是沿海地区的传统发酵调味品。
dab: v; n
表示" 轻触,轻拍; 比目鱼"，means "hit lightly; a light touch or stroke"，如：She gave me a dab with her umbrella.她用雨伞轻轻拍了我一下。Dab the coffee off with your handkerchief. 用你的手帕把咖啡擦掉。
preexist: v
表示" 先前存在"，means "exist beforehand or prior to a certain point in time"，如：Somatic cells are produced from preexisting cells. 体细胞产生自原始细胞。
placebo: n
表示" 安慰剂；安慰话"，如：The placebo has been found to work with a lot of different cases. 人们已发现安慰剂能在很多不同的病例中发挥作用。
episodic: adj
表示"插曲式的；偶然发生的"，means "of writing or narration; divided into or composed of episodes"，如：The book is episodic and the incidents don't always hang together.这本书是插话式的,事件并不总是连贯发生的
inhibitory: adj
表示" 禁止的；抑制的"，means "restrictive of action"，如：The present results have demonstrated that PRN also plays an inhibitory role in a variety of behavioral functions. 目前实验结果证实其对多种行为量测也有抑制的作用。
fiery: adj
表示"火的, 炽热的；易怒的，暴躁的"，means " flaming;looking like fire; "，如：She has fiery red hair. 她有着火红的头发。No one dare to offend the fiery person. 没人敢惹这个脾气急躁的人。
antimicrobial: n; adj
表示" 抗菌剂,抗菌药; 抗菌的"，如：The book has been updated throughout, and changes to antimicrobial drug prescribing regimens have been included. 书更新全部，并且已经包括换抗菌药规定生活制度。
pathogen: n
表示" 病原体"，如：The opposite end latches onto the pathogen. 相对的一端锁在病原体上。
dropout: n
表示" 退学学生；拒绝传统社会的人"，如：He is a dropout, and messes around all day. 他是一名退学生，整天游手好闲。
rub: v; n
表示"擦,摩擦；困难，阻碍"，means ""，如：I rubbed the window with a cloth. 我用一块布擦窗子。We need money badly, but there's the rub: no one will lend us any. 我们急需要钱,但困难的是:谁也不会借钱给我们。
tangy: adj
表示" 强烈的；扑鼻的；"，means "tasting sour like a lemon"，如：I love the tangy smell of the sea air when I go to the beach. 我去海边的时候很喜欢海风这种强烈的气息。
impostor: n
表示" 冒充者；骗子"，means "a person who makes deceitful pretenses"，如：He said he was a doctor, but it subsequently emerged that he was an impostor. 他说他是位医生，但后来却发现他是个骗子。
gravel: n
表示" 碎石"，means "a mixture of small stones with sand,used on the surface of roads or paths"，如：The water is infiltrating the gravel bed. 水正渗透进碎石底层。
stubbly: adj
表示"多断株的；断株一般的"，means "having a short growth of beard"，如：Look at that slightly stubbly chin. 看那下巴上精心修过的胡渣。
rhizome: n
表示" [植]根茎；地下茎"，means ""，如：The plant has a succulent rhizome.这种植物有肉质根茎。
中文简要说明：
下次吃生鱼片、寿司或日式荞麦面遇上正牌的「哇沙比」山葵泥，可别搁着不碰了，它不仅能增添风味、去腥杀菌，同时可能也降低了失智风险。日本东北大学合作研究成果显示，长者每天吃少量山葵萃取物，3个月之后，短期、长期记忆力与认知能力均见显著改善。
综合《日本时报》、美国哥伦比亚新闻网（CBS News）报导，日本东北大学这项研究重点在于日本山葵根茎部一种已知有抗氧化、抗发炎效果的活性成分「异硫氰酸6-亚磺酰基」（hexaraphane，6-MSITC），研究团队想知道这种化合物对于60岁以上健康长者认知功能有无正面影响。
研究以双盲、随机方式进行，72名60岁至80岁身体健康的受试者分为两组，一组每天服用0.8毫克6-MSITC当作营养补充剂（相当于5公克山葵），另一组服用安慰剂。12周过后执行认知测验结果显示，实验组受试者的事件记忆（episodic memory）与工作记忆（working memory）均比服用安慰剂的受试者有显著的进步。
主持这项研究的东北大学老年医学发展研究所副教授野内类专门研究失智症预防，他发现地中海饮食、运动、音乐等疗法的放弃比例很高，因而投入山葵相关治疗研究。野内认为，每天服用补充剂对老人家而言更容易持续，山葵的抗发炎、抗氧化效果比生姜、姜黄更好。
野内说，此前已有动物实验显示山葵有益健康，但令研究团队惊讶的是，本次研究受试者的改变非常大，进步显著。这项研究的赞助者、总部位于爱知县名古屋的金印公司表示，研究成果可用于研发增强记忆力新产品，利用山葵的好处增进老年人的预期寿命与福祉。
不过，正牌山葵普及率并不高，市售山葵泥几乎都是另一种植物辣根加了食用色素制成的「冒牌货」。山葵原产于日本，不易栽种，需要将近2年方能成熟，需要严格控制温度、遮荫、土壤、水分，价格不斐，必须现磨现吃；以东北大学试验剂量而言，只需要吃少量山葵泥即可获得相同益处。
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