Glance through a popular magazine’s listof healthy breakfast foods and you’ll likely find oatmeal in the group. Among other benefits, oatmeal is touted as having the ability to keep you full, effectively squelching the desire for that midmorning snack. In fact, a group of researchers recently found that a serving of instant oatmeal decreased the desire to eat more than the same amount of Honey Nut Cheerios, an oat-based cereal. I decided to talk with lead author Candida Rebello of the Pennington Biomedical Research Center to find out what makes oatmeal so special.

The story begins with dietary fiber, the part of plant foods that the body can’t digest, which has been shown to promote a feeling of fullness. Both the oats in oatmeal and ready-to-eat oat-based cereals contain β-glucan, a type of soluble fiber.

However, it’s not just the fiber content that matters, according to Rebello and her fellow researchers. Fullness and the desire to eat may also be influenced by a property of fluids called viscosity, which, in this case, is generated by oat β-glucan. Rebello described viscosity as the slimy feel of oatmeal that you can both see in the bowl and feel in your mouth. Scientists think viscosity affects appetite by influencing the way foods interact with the mouth, as well as the stomach and intestines. For example, increased viscosity in the intestinal tract can stimulate the release of appetite-regulating hormones. The oral and gastric effects work together, according to Rebello, meaning a food with both a high initial viscosity in the mouth and a high subsequent viscosity in the gastrointestinal tract will likely produce a greater feeling of fullness.

The study Rebello and colleagues recently authored looked at instant oatmeal, old-fashioned oatmeal and Honey Nut Cheerios and measured each food’s viscosity and effect on satiety. (I should note that though Rebello works for the Pennington Biomedical Research Center, the study was a collaborative effort with researchers from PepsiCo R&D Nutrition and was funded by PepsiCo R&D Nutrition’s Quaker Oats Center of Excellence.)

The researchers found that instant oatmeal improved several measures of satiety, or the feeling of fullness, over a four-hour period more than Honey Nut Cheerios did. Old-fashioned oatmeal improved one measure of satiety when compared to Honey Nut Cheerios. As might be expected, the study found that instant oatmeal had greater initial and subsequent viscosity compared to Honey Nut Cheerios. Old-fashioned oatmeal had greater subsequent viscosity but not higher initial viscosity, which could explain why it was less effective at promoting fullness.

Viscosity of oatmeal or cereal appears to be a key player in promoting fullness, so my next question was naturally about what determines differences in viscosity.

“Viscosity is generated by the particular fiber in oatmeal, which is called β-glucan,” said Rebello, who is a research dietitian. “The fiber is affected by the manner in which it is processed.”

Ready-to-eat oat-based cereals, instant oatmeal and old-fashioned oatmeal are processed differently, which can lead their β-glucan to have a different structure and result in a different viscosity.

So if you find yourself feeling satisfied until lunch after a bowl of instant oatmeal, now you’ll know why.


參考譯文
據(jù)《科學(xué)美國(guó)人》（Scientific American）25日?qǐng)?bào)道，隨便看看流行雜志列出的健康早餐食物，你總會(huì)發(fā)現(xiàn)燕麥的身影。燕麥有很多益處，其中之一就是它能夠讓你有飽腹感，能有效地阻止你在早上10-11點(diǎn)吃零食的欲望。其實(shí)，一些研究人員最近發(fā)現(xiàn)比起同量的蜂蜜堅(jiān)果麥片（含燕麥的谷物），一份速食燕麥更能降低人的食欲。我決定采訪一下潘寧頓生物研究中心的主任卡迪達(dá)·瑞伯樂（Candida Rebello），看看到底是什么讓燕麥如此特別。

一切要從食物纖維說起。食物纖維是植物性食物不能被人體消化的那部分，正是這一部分提高了人的飽腹感。燕麥片中的燕麥和含燕麥的即食谷類食物都含有可溶纖維beta葡聚糖。

但是，瑞伯樂和其同事的研究發(fā)現(xiàn)，纖維不是讓人產(chǎn)生飽腹感的唯一原因。一種粘稠狀液體也可以影響飽腹感和食欲。這種粘液就是由beta葡聚糖產(chǎn)生的。瑞伯樂解釋道，這種粘液就像燕麥片的那種滑膩的感覺，不管是裝在碗里還是吃進(jìn)口里你都能感到這種滑膩感。科學(xué)家們認(rèn)為粘液是通過影響食物與嘴和胃與腸接觸的方式來影響食欲的。比如，腸道內(nèi)粘液增多會(huì)刺激調(diào)解食欲的荷爾蒙分泌。瑞伯樂說，口感和胃部感受共同作用使人產(chǎn)生了飽腹感。也就是說，能夠讓人首先在嘴里感受到高粘稠度，其次再在腸胃中保持高粘稠度的食物很可能引起人的飽腹感。

瑞伯樂及其同事們最近聯(lián)名發(fā)表的一項(xiàng)研究觀察了速食燕麥，傳統(tǒng)燕麥和蜂蜜堅(jiān)果燕麥飲品，測(cè)量了每一種食物的粘稠度和帶來的滿足感。（我要事先聲明：雖然瑞伯樂在潘寧頓生物研究中心工作，但是這份研究報(bào)告是他和百事公司營(yíng)養(yǎng)研發(fā)部的研究人員一起撰寫而成，這項(xiàng)報(bào)告也是由百事公司營(yíng)養(yǎng)研發(fā)部旗下的桂格優(yōu)質(zhì)燕麥中心出資贊助的。）

研究者發(fā)現(xiàn)，在四個(gè)小時(shí)內(nèi)，速食燕麥能大大提高滿足感，也就是飽腹感，相比起來蜂蜜堅(jiān)果燕麥飲品的效果比速食燕麥低很多。傳統(tǒng)燕麥比燕麥飲品效果好一些。跟預(yù)期一樣，研究發(fā)現(xiàn)速食燕麥比燕麥飲品的原始粘稠度和進(jìn)入腸胃后的粘稠度都要高。傳統(tǒng)燕麥片原始粘稠度低，而進(jìn)入腸胃后的粘稠度高。這就是它為什么在增加飽腹感的效果上要比速食燕麥稍遜一籌的原因。

燕麥片或者谷物的粘稠度似乎在促進(jìn)飽腹感方面是至關(guān)重要的原因，所以我的下一個(gè)問題自然就是粘稠度的高低是由什么決定的。

作為一名做研究的飲食學(xué)家，瑞伯樂解釋說：“粘稠度是由燕麥片中一種叫做beta葡聚糖的特殊纖維產(chǎn)生的。這種纖維會(huì)受到處理方式的影響.

即食燕麥谷物類食品，即食燕麥和傳統(tǒng)燕麥的處理方法不同，那么他們中所含的beta葡聚糖的結(jié)構(gòu)也就不同，導(dǎo)致他們的粘稠度也不一樣。

所以如果你發(fā)現(xiàn)自己吃了一碗速食燕麥片后到午飯時(shí)間都還不餓，現(xiàn)在你應(yīng)該知道其中的原因了吧。