為什麼多飽都能再吃塊甜點？研究：“甜點胃”有科學依據！

你是否有過這樣“甜蜜的煩惱”呢？

“明明剛吃完火鍋，看到提拉米蘇卻還能再戰三百回合”。據說每個人都有兩個“胃”，一個用來吃飯，一個用來吃甜點。無論吃得有多撐，永遠有甜點的一席之地。

Have you ever pondered the phenomenon of consistently finding room for dessert when the dessert menu is presented? Researchers may have unraveled this mystery. The researchers at the Max Planck Institute for Biology of Ageing have discovered that the nerve cells responsible for inducing satiety post-meal also play a role in triggering sweet cravings following a meal.

大腦對甜食很“雙標”

科學家們發現：人類對甜食的執念，竟是源於神經系統的“雙重欺騙”。大腦中本該抑制食慾的關鍵神經元，在面對甜食時，卻會刺激食慾，告訴大腦“我還能吃”。

德國馬克斯·普朗克代謝研究所科研團隊稱，我們的POMC神經元具有“雙重身份”。通常在我們吃飽喝足時，下丘腦中抑制食慾的神經元——POMC神經元，會被啟用併發出“停止進食”的訊號，就像在對身體說“別再吃了”。而即使吃飽了，在甜食麵前，POMC神經元卻會“背叛”身體，一反常態，改為促進釋放β-內啡肽刺激進食慾望。

A report describes "a subset of neurons located in the hypothalamus—a deep brain region—that typically signal to us to stop eating post-meal. These neurons were found to drive sugar consumption in mice even post-satiation." Through brain imaging, researchers observed similar mechanisms in humans.

北京大學人民醫院劉健教授解釋：“β-內啡肽與大腦的獎勵中心相互作用，製造愉悅記憶，讓我們在吃甜食時覺得又開心又滿足。這本質上是一種進化機制——在食物匱乏時期，促使人類優先獲取高熱量資源。”

甜食會改變我們的大腦

發表在《細胞代謝》期刊上的一項研究顯示：高脂肪和高糖食物會改變我們的大腦。如果經常吃，即便是少量食用，未來大腦也會精準地提醒人們再次食用這些高糖高脂食物。研究人員解釋：當人們天天食用高糖高脂食物後，大腦會建立連線，下意識地偏愛這些食物，更喜歡選擇高脂高糖的食物。

Sugar overconsumption is one of the main drivers of poor health conditions such as obesity, Type 2 diabetes and cardiovascular disease. "What we choose to eat is controlled by our brain, but not all foods are equally 'rewarding' for the brain."

對甜食的偏愛“經久不衰”，和腸道神經也有關。研究發現，一旦甜食進入胃腸道，腸腦軸就會被啟用。腸腦軸是指腸道和大腦之間透過神經、內分泌和免疫等多種機制形成的雙向交流系統，不僅調節著機體的消化、吸收、代謝等生理功能，還深刻影響著情緒、認知、行為等心理過程。腸道神經受到刺激，大腦隨之釋放攝入更多糖的訊號，使“甜食偏好”持續存在。

如何科學有效剋制“糖癮”

《中國居民膳食指南(2022)》推薦，糖攝入量每天不超過50克，最好控制在25克以內。控制“糖癮”，最好從以下5件事入手。

▌增加膳食纖維攝入

血糖波動正是引發糖癮的元兇，而我們可以透過提高膳食纖維攝入來預防血糖驟升。常見的高膳食纖維食物有洋蔥、大蒜、蘆筍、蘋果等。這些食物中的益生元纖維可透過改變腸道菌群直接影響大腦神經活動，使人體對甜食的渴望降低。

Research has also found that eating prebiotic fibre, found in foods like onions, garlic, asparagus and apples, causes changes in the gut bacteria that directly affect the brain, making you less likely to crave sugary foods. Switch to wholegrain bread, rice and pasta and leave the skins on potatoes for an immediate fibre boost.

▌足量攝入優質脂肪與蛋白質

每餐需確保優質脂肪與蛋白質的足量攝入。這兩類營養素能在餐後顯著延長飽腹時間、增加飽腹感，將對於飯後甜點的渴望降低。

Healthy fats, in the form of full-fat dairy, nuts, avocados and olive oil, and protein in nuts, eggs, fish and beans, are important in determining how satisfied you feel, so try to include them in every meal.

▌優先選用純天然未加工的食物

超加工食品的成癮性已獲科學驗證——食品製造商透過精確調控“糖-鹽-脂肪”的黃金比例，刻意啟用大腦愉悅中樞，這種令人慾罷不能的配比被稱為“極樂點”（the bliss point）。研究表明，持續攝入超加工食品會使大腦獎賞系統敏感度降低，導致對天然甜味的感知閾值不斷提高。

▌建立“正念飲食觀”

營養師指出，大部分的甜食渴求實為情緒性進食。當人體處於壓力狀態時，皮質醇水平升高會觸發對快速能量的需求，這種生理機制往往被誤判為飢餓感。值得注意的是，情緒化攝入甜食後，有部分個體會產生自責情緒，反而加劇心理壓力。

Try eating mindfully: we often eat a sugary snack because we are not tuned into our body's hunger signals. So before reaching for that biscuit, ask yourself these questions: How hungry am I on a scale of one to 10? If it's less than eight, you're not really hungry. Am I just bored or in need of a break? Perhaps have a cup of tea instead. Can I ride this out until the next meal?

▌吃甜點的時候，盡情地享受它

當選擇享用甜點時，應當透過提升進食儀式感來獲得更大滿足，而非陷入“偷吃-愧疚”的惡性迴圈。研究顯示，專注進食可提升多巴胺分泌效率，這意味著更小的分量就能獲得同等的愉悅感。

Use a plate, sit down and enjoy your snack. You can make more nutritious sweet treats too. Have a square of dark chocolate with a teaspoon of nut butter to satisfy your sweet tooth in a more sustaining way. To put it simply, a holistic approach is the best way to deal with sugar cravings.