Homma Kazuhiro, Wakana Noriaki, Suzuki Yoshimi, Nukui Mai, Daimatsu Takaki, Tanaka Etsuro, Tanaka Kazuo, Koga Yasuhiro, Nakajima Yukiko, Nakazawa Hiroe
Department of Nutritional Science, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8 502, Japan.
J Nutr Sci Vitaminol (Tokyo). 2006 Oct;52(5):297-301. doi: 10.3177/jnsv.52.297.
The purpose of this study is to find a method of cooking natto that prevents the appearance of high-plasma vitamin K concentrations after the consumption of natto, so that patients taking warfarin can benefit from eating natto. Five cooking methods were examined to determine which could most effectively decrease the count of the living Bacillus subtilis in natto. Volunteers ate natto or treated natto, and their plasma vitamin K level was measured at 5, 8, 24 and 48 h thereafter. One gram of natto contained 9.7+/-0.1 Log cfu/mL of Bacillus subtilis. Boiling significantly reduced the Bacillus subtilis count to 5.1+/-0.3 Log cfu/mL, and concomitantly reduced the content of menaquinone-7 (MK-7), which is a form of vitamin K synthesized by Bacillus subtilis, from 660.40+/-65.32 ng/mL to 78.50+/- 11.12 ng/mL. Untreated natto increased the MK-7 concentration in blood from 1.86+/-1.51 ng/mL to 14.54+/-4.12 ng/mL at 5 h after intake, and the MK-7 concentration remained elevated at 8, 24 and 48 h (7.29+/-2.20, 6.97+/-2.60, and 5.37+/-1.94 ng/mL, respectively). In contrast, boiled natto increased plasma MK-7 only mildly (from 1.61+/-1.11 to 4.02+/-0.82 ng/ mL at 5 h) and the concentration remained relatively stable up to 48 h (3.46+/-0.83, 4.22+/-1.51 and 2.77+/-0.75 ng/mL at 8, 24 and 48 h, respectively). In conclusion, boiled natto did not cause a marked increase in the plasma concentration of vitamin K in subjects who consumed it. Thus, patients on warfarin may be able to eat boiled natto without ill effects.
本研究的目的是找到一种纳豆烹饪方法，以防止食用纳豆后出现高血浆维生素K浓度的情况，从而使服用华法林的患者能够从食用纳豆中获益。研究考察了五种烹饪方法，以确定哪种方法能最有效地减少纳豆中活的枯草芽孢杆菌数量。志愿者食用纳豆或经过处理的纳豆，并在之后的5、8、24和48小时测量他们的血浆维生素K水平。每克纳豆含有9.7±0.1 Log cfu/mL的枯草芽孢杆菌。煮沸显著降低了枯草芽孢杆菌数量至5.1±0.3 Log cfu/mL，同时将由枯草芽孢杆菌合成的维生素K的一种形式——甲基萘醌-7（MK-7）的含量从660.40±65.32 ng/mL降至78.50±11.12 ng/mL。未处理的纳豆在摄入后5小时使血液中MK-7浓度从1.86±1.51 ng/mL升高至14.54±4.12 ng/mL，并且在8、24和48小时时MK-7浓度仍保持升高（分别为7.29±2.20、6.97±2.60和5.37±1.94 ng/mL）。相比之下，煮沸的纳豆仅使血浆MK-7略有升高（5小时时从1.61±1.11升高至4.02±0.82 ng/mL），并且该浓度在48小时内保持相对稳定（8、24和48小时时分别为3.46±0.83、4.22±1.51和2.77±0.75 ng/mL）。总之，煮沸的纳豆不会使食用它的受试者血浆中维生素K浓度显著升高。因此，服用华法林的患者或许能够食用煮沸的纳豆而无不良影响。
