本帖最後由 sammy 於 2010-5-27 23:50 編輯
最近讀到一本多年前的暢銷書寫關於微波爐加熱會令食物變質的「真相」：
「不少專家做了很多臨床實驗來證明這些食物是如何變質的，其中包括胺基酸出現的同質異構(isomeric)變化，把左旋(L-form) 的易吸收形態變為不易吸收的右旋(D-form) 。例如肉類的精氨酸L-Arginine變為D-Arginine，長期服此形態的肉類對健康會有很大影響，亦可能會間接做成腸癌。
......在1989年12月9日出版的《刺血針》(Lancet) 醫學雜誌內，來自夏威夷的Dr. Lita Lee撰文指出若然用微波爐煮育嬰奶粉，會令其中的輔胺酸L-Proline變成D-Proline，而這種D型同質異構的物質已證實可以危害大腦及腎臟。」
我很震驚，因為用了微波爐好幾年了。雖然素聞微波爐食物有害健康，但沒放在心裏。現在出自醫生之口，刊之於書，令我認真起來。不過經查明後，我更震驚。
如果大家去Lancet查1989年12月9日Vol 334 No. 8676, 根本沒有Dr. Lita Lee的文章, 相關的只有"AMINOACID ISOMERISATION AND MICROWAVE EXPOSURE" G. Lubec, Chr. Wolf, B. Bartosch:
http://www.thelancet.com/journals/lancet/issue/current?tab=past
為何引錯？原來網上到處流傳以下的句子：
Dr. Lita Lee of Hawaii reported in the December 9, 1989 Lancet:"Microwaving baby formulas converted certain trans-amino acids intotheir synthetic cis-isomers......
不過根據Dr. Lita Lee夫子自道(http://www.litalee.com/shopexd.asp?id=182)
"To this list, I will add results reported in the December 9, 1989 Lancet. Microwaving baby formulas converted certain trans-amino acids into their synthetic cis-isomers. "
作者其實只是引述Lancet文章，不知誰是始作俑者，以致謬種流傳。
至於Lubec G, Wolf C, Bartosch B的文章，其實是沒有審查過的letter to the editor，只是初步發現，後來證實要改變分子的微波劑量比家用微波爐高得多，所以不足為慮。原文如下:
AMINOACID ISOMERISATION AND MICROWAVE EXPOSURE
Sir, -Microwaves are used for cooking and for scientific purposes. One application is the hydrolysis of peptides and proteins.1 To see if such hydrolysis alters aminoacids by isomerization or degradation we did the following study on three different milk formulae.
Formulae were tested in their native state, hydrolysed conventionally by 6 mol/l hydrochloric acid at 105ºC for 16 h, heated for 10 min in a microwave oven used for heating of infant food or heated to 80ºC in a water bath for the same period.
4 and 3 trans-hydroxyproline and 3 and 4 cis-hydroxyproline were measured by thin-layer chromatography.2 The results were checked by gas chromatography and mass spectrometry and by high pressure liquid chromatography (HPLC).3 The same samples were studied by HPLC with ‘Cyclobond I’ β-cyclodextrin columns4 to obtain D and L aminoacid separation. As marker, D-proline was used.
Free aminoacids in milk formulae, conventionally hydrolysed milk samples and conventionally heated milk samples did not contain cis-3 or cis-4 hydroxyproline. However, all three formulae contained cis stereoisomers of hydroxyproline after microwave treatment and the microwave treated samples were the only specimens in which D-proline was found on HPLC; concentrations of cis-isomers were 1-2mg/l.
The conversion of trans to cis forms could be hazardous because when cis-aminoacids are incorporated into peptides and proteins instead of their trans isomers this can lead to structural, functional, and immunological changes. 5,6
The fact that L-proline was converted to D-proline should also be taken into account. D-proline is neuroxocic,7 and we have reported nephrotoxic and hepatoxic effects of this compound.8
We therefore advise further studies on the molecular changes of aminoacids and other compounds because so little has been published about this aspect of microwave treatment.9
Department of Paediatrics,
University of Vienna
A-1090 Vienna, Austria
G. Lubec
Chr. Wolf
B. Bartosch
先是穿井得人，繼而人云亦云，一笑。 |
提升卡
置頂卡
沉默卡
喧囂卡
變色卡
顯身卡
