为什么生酮饮食可能有助于对抗糖尿病和癌症

Why the ketogenic diet may help fight diabetes, cancer

　

　

 

脂肪含量极高的饮食似乎不是减肥的最佳方式。但越来越多的研究表明，高脂肪、低碳水化合物的生酮饮食不仅有利于减肥，还可能有助于预防疾病。

　

　

 

生酮饮食(Keto)依赖于将脂肪作为燃料，而不是碳水化合物或蛋白质中的葡萄糖。简单地说，每天的生酮饮食包括75%的脂肪，20%的蛋白质和少量的碳水化合物，大约5%。这种主营养素的平衡是为了使你的身体处于酮症状态，从而抑制胰岛素和血糖水平的释放。酮症对你的健康的好处是改善生物标志物，如血糖，降低血压和减少食欲，因为饱腹感与消耗脂肪有关。

 

你可能认为这听起来很像阿特金斯饮食法（Akins Diet）——其实不然。主要区别在于饮食中的蛋白质含量。阿特金斯倾向于非常高的蛋白质，而生酮是中等的。

　

 

生酮饮食你几乎每餐都可以吃黄油，但不能吃面包。

 

这并不是一个容易遵循的计划，但是酮症作为一种可能的预防疾病的理论正在引起癌症专家的注意。肿瘤免疫学家Patrick Hwu博士是美国领先的癌症专家之一尽管他更愿意称其为“燃烧脂肪的新陈代谢饮食”，或者“燃烧脂肪的饮食”，但他已经追随酮饮食4年了。还需要更多的研究来证明它的益处，但是休斯顿MD安德森癌症医学中心的主任Hwu在看到自己的健康状况有所改善后，还是相信它。

 

为什么生酮饮食有效果？

人体首选和首选的燃料是葡萄糖——以糖原的形式储存。任何时候你吃碳水化合物，无论是扁豆还是甘草，身体都会将其转化为葡萄糖或糖。由于人体不能很好地利用血液中的大量糖分，一种叫做胰岛素的激素从胰腺分泌出来，让糖分进入细胞。

 

生酮饮食的支持者说，高碳水化合物饮食的问题是它会导致高胰岛素水平，并使身体燃烧糖和碳水化合物而不是脂肪。相反，在低碳水化合物饮食中，身体会优先学会燃烧脂肪。当这种情况发生时，被称为酮体的酸从脂肪中释放到体内，而胰岛素水平下降。在低碳水化合物饮食几天后就会发生酮症。

 

低碳水化合物的生酮食物包括:

坚果，尤指澳洲坚果、山核桃和巴西坚果

种子

鳄梨

橄榄油和椰子油

非淀粉蔬菜

鸡蛋

 

对于Hwu来说，典型的一日三餐包括:

早餐

一杯加了大量鲜奶油、甜菊糖和不加糖的杏仁奶的咖啡

 

午餐

绿色蔬菜如菠菜、西葫芦或花椰菜，控制部分肉类

 

晚餐

绿色蔬菜和一小部分豆腐

黄油，不含面包，几乎每顿饭都要大量使用。

 

他定期吃不加糖的椰奶冰激凌，但尽量远离水果，Hwu认为水果是“大自然的糖果”。因为它不是甜的饮料，像红酒这样的酒精是可以的。

 

Hwu不吃低脂和脱脂食品，认为奶酪和奶油奶酪是完美的食物，而澳洲坚果或鳄梨沙拉酱——搭配黄瓜或芹菜而不是薯片——是理想的零食。

　

 

面包、面食、高蛋白食物和糖果都是不推荐的——尽管你可以吃可可。典型的Keto早餐是用椰子油和培根做的鸡蛋。没有麦片。

 

碳水化合物需要适量摄入，纤维含量要高。

 

如何对抗疾病

根据Hwu的说法，癌症喜欢各种来源的糖，并以一种有助于癌细胞生长的方式进行代谢。癌细胞可以在葡萄糖、胰岛素和一种与新陈代谢有关的激素——胰岛素样生长因子1 (IGF-1)的作用下茁壮成长。

 

需要进行研究来研究这种饮食是否能抑制癌细胞，但是生酮饮食可以降低胰岛素和IGF-1的水平。例如，在2017年的一项研究中，参与者禁食，在禁食期间不摄入碳水化合物，降低了血压、炎症水平、空腹血糖和IGF-1水平。

　

　

　

 

理想的临床研究将是一项对照试验，在此试验中，具有相似癌症的患者将随机获得不同种类的饮食，然后对其癌症进行密切监测。

 

Hwu相信心血管疾病和糖尿病的风险——这两者都与高血压、葡萄糖和胆固醇相关——可以通过研究发现，遵循生酮饮食来降低。约翰霍普金斯大学(Johns Hopkins)最近的一项研究发现，生酮饮食不仅安全，而且对患有某些严重癫痫的成年人也有效，这支持了先前的研究。

 

“酮流感KETO”

 

由于这种饮食限制太大，在服用后的最初几周内，许多人都经历了足以被称为“酮流感”的副作用。

 

症状通常在4到7天后消失，范围从失眠、头痛、口臭和便秘。1型糖尿病患者、肾病患者和孕妇应避免生酮饮食。

 

减少蛋白质摄入是饮食中最大的挑战之一。因为饮食中高水平的蛋白质会在一个叫糖异生的过程中转化为葡萄糖，所以Keto理论认为饮食中过多的蛋白质意味着过多的葡萄糖，从而使你脱离酮症。这就是为什么培根比鸡胸肉更受欢迎的原因，因为它脂肪含量高，但蛋白质含量低。

 

还有一个常见的担忧是生酮饮食可能导致酮症酸中毒，当血液中的酸度增加时就会发生。糖尿病酮症酸中毒是一种威胁生命的疾病，由高糖和胰岛素依赖型糖尿病患者的胰岛素不足引起，这与低碳水化合物、高脂肪饮食中燃烧脂肪的新陈代谢产生的酮类物质的状态非常不同。

 

因为我从来不会让我的病人尝试我自己没有尝试过的饮食，所以我坚持自己30天的生酮饮食实验。请继续关注;我将在以后的帖子中分享我的这个月的结果。

 

克里斯汀Kirkpatrick, 医学学士，注册营养师，他是俄亥俄州克利夫兰诊所健康研究所(Cleveland Clinic wellness Institute)的健康营养服务部经理，著有《瘦肝》(Skinny Liver)一书。在Twitter上关注她@KristinKirkpat。想要了解更多的饮食和健身建议，请注册我们的“一件小事”时事通讯。

　

 

Why the ketogenic diet may help fight diabetes, cancer

by Kristin Kirkpatrick / Nov.06.2017 / 11:27 PM ET / Updated Ja

n.04.2018 / 10:42 PM ET / Source: TODAY

A diet extremely high in fat may not seem like the best way to lose fat. But there’s a growing body of research showing that the high-fat, low-carbohydrate ketogenic diet is not only good for weight loss, but also may help in preventing disease.

 

The ketogenic diet, or keto, relies on using your fat as fuel, instead of glucose from carbohydrates or protein. Simply put, the daily ketogenic diet consists of 75 percent fat, 20 percent of protein, and a teeny allotment of carbohydrates, about 5 percent. This balance of macronutrients is intended to put your body in a state of ketosis, which suppresses the release of insulin and blood glucose levels. The benefits of ketosis to your health are improvements in biomarkers like blood glucose, reduction of blood pressure and decreased appetite due to fullness linked to consumption of fats.

 

You might think this sounds a lot like the Atkins diet — it’s not. The main difference lies in the protein content of the diet. Atkins tends to be very high in protein, while ketogenic is moderate.

 

A full pack of unwrapped butterOn the ketogenic diet you can have butter with most every meal, but no bread.Getty Images stock

It's not the easiest plan to follow, but the theory of ketosis as a possible prevention against disease is gaining attention from cancer specialists. Tumor immunologist Dr. Patrick Hwu, one of the leading cancer specialists in the U.S., has followed the keto diet for four years, although he prefers to call it the fat-burning metabolism diet, or fat-burning diet. More research is needed to prove its benefits, but Hwu, the head of cancer medicine at MD Anderson in Houston, believes in it after seeing improvements in his own health.

 

WHY KETO WORKS

 

The body’s first and preferred fuel of choice is glucose — stored as glycogen. Anytime you eat a carbohydrate, be it lentils or licorice, the body turns it into glucose, or sugar. Because the body does not do well with a lot of sugar in the blood, a hormone called insulin is secreted from the pancreas, and allows the sugar to enter the cells.

 

 

 

Proponents of the ketogenic diet say the problem with a high-carbohydrate diet is that it induces high insulin levels and keeps the body burning sugar and carbs instead of fat. In contrast, on a low-carb diet, the body learns to burn fat preferentially. When this happens, acids known as ketones are released from fat into the body, while insulin levels go down. Ketosis can occur after several days on a low-carb diet.

 

Low carb, ketogenic foods include:

 

nuts, especially macadamia, pecan, and brazil nuts

seeds

avocado

olive and coconut oil

non-starchy vegetables

eggs

For Hwu, a typical day's meals include:

 

BREAKFAST

 

A cup of coffee with heavy whipping cream, stevia drops, and unsweetened almond milk

 

LUNCH

 

Greens like spinach, zucchini or broccoli, with a controlled portion of meat

 

DINNER

 

Green vegetables with a small portion of tofu

 

Butter, without the bread, is used liberally with almost every meal.

 

He indulges periodically on no-added sugar coconut milk ice cream bars, but tries to stay away from fruit, which Hwu considers “nature’s candy”. As it’s not a sweet drink, alcohol such as red wine is OK.

 

Hwu avoids low-fat and fat-free items, thinks cheese and cream cheese are perfect foods, and macadamia nuts or guacamole — with cucumber or celery but not chips — are ideal snacks.

 

Bread, pasta, very high protein options and candy are discouraged — although you can have cacao. A typical keto breakfast is eggs cooked in coconut oil and bacon. No cereal.

 

Carbs need to be consumed in moderation and to be high in fiber.

 

HOW IT MIGHT FIGHT DISEASE

 

According to Hwu, cancer loves sugar from all sources, and metabolizes it in a way that helps the cancer cell thrive. Cancer cells can thrive on glucose, insulin, and a hormone associated with metabolism called insulin-like growth factor 1, or IGF-1.

 

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Studies are needed to investigate whether the diet can specifically inhibit cancer cells, but the ketogenic diet is shown to reduce levels of insulin and IGF-1. For example, a 2017 study in which participants fasted, omitting carbohydrates during their fasting times, reduced their blood pressure, levels of inflammation, fasting blood glucose and levels of IGF-1.

 

The ideal clinical study would be a controlled trial where patients with similar cancers would be randomized to get different kinds of diets, followed by close monitoring of their cancers.

 

Hwu believes risks of cardiovascular disease and diabetes — which are both associated with high blood pressure, glucose and cholesterol — may be reduced by following the ketogenic diet, based on research. A recent study from Johns Hopkins found a ketogenic diet was not only safe, but effective for adults who had certain severe forms of epilepsy, supporting previous research.

 

‘KETO FLU’

 

Because the diet is so restrictive, in the first few weeks of following it many people experience side effects bad enough to be known as “the keto flu.”

 

Symptoms, which usually go away after four to seven days, can range from: insomnia, headaches, bad breath and constipation. Type 1 diabetics, individuals with kidney disease and pregnant women should avoid the ketogenic diet.

 

Cutting back on protein is one of the largest challenges to the diet. Because high levels of protein in the diet can turn into glucose in a process called gluconeogenesis, the keto theory says too much protein in the diet can mean too much glucose, whisking you out of ketosis. That’s why bacon, which has a ton of fat but not a lot of protein is a preferred food over chicken breast, which is high in protein with very little fat.

 

There is also a common worry the ketogenic diet may cause ketoacidosis, which occurs when the acidity in the blood increases. Diabetic ketoacidosis is a life-threatening condition caused by very high blood sugars and a deficiency of insulin in insulin-dependent diabetics, a very different state from ketones produced by a fat-burning metabolism on a low-carb, high-fat diet.

 

Since I’ve never put a patient on a diet I have not tried myself, I'm following my own 30-day experiment with the ketogenic diet. Stay tuned; I’ll be sharing how my month turns out in a future post.

 

Kristin Kirkpatrick, MS, R.D., is the manager of wellness nutrition services at the Cleveland Clinic Wellness Institute in Cleveland, Ohio, and the author of "Skinny Liver." Follow her on Twitter @KristinKirkpat. For more diet and fitness advice, sign up for our One Small Thing newsletter.

 

https://www.today.com/health/ketogenic-diet-how-high-fat-low-carb-eating-may-fight-t118177