Nature：过量食用含糖食物是一种慢性自杀

近日，加利福尼亚大学旧金山分校的研究人员在新一期英国学术刊物《自然》上发表论文指出，糖就像烟草和酒精一样，是一种有潜在危害且容易让人上瘾的物质。研究人员呼吁，各国应像对待烟酒那样采取加税等限制措施，严格控制人们摄入糖类。

研究发现，糖对人类的影响不仅是产生“空热量”（即含有高热量却缺乏基本维生素、矿物质和蛋白质的现象）导致发胖，而且糖会干扰激素，向大脑发送“继续摄入”的信号，让人们对其上瘾，产生依赖，就像烟瘾和酒瘾一样。糖还会干扰代谢、使血压升高并可能损害肝脏，是威胁人类健康的“主犯”之一。

论文的主要作者、加利福尼亚大学旧金山分校的内分泌学家罗伯特·勒斯蒂格说，“糖在肝脏中代谢，肝脏会将糖转化成脂肪，造成胰岛素抵抗，从而导致代谢综合征，引发各种疾病”，因此糖的摄入应严格限制。

研究指出，一些国家对糖这种影响健康的物质缺乏管理。糖被添加在大量食物中，因此必须采取社会干预手段。研究人员呼吁各国采取与限制烟酒类似的做法，如加税、年龄管制、在学校周围禁止销售等，以控制糖在全球范围内的使用。

相关研究指出，过去50年内，全球糖消费量激增3倍，糖摄入过多造成的肥胖症、糖尿病、心脏病和肝病等疾病在全球高发，每年间接导致全球约3500万人死亡。

Public health: The toxic truth about sugar

Robert H. Lustig,  Laura A. Schmidt  & Claire D. Brindis

Last September, the United Nations declared that, for the first time in human history, chronic non-communicable diseases such as heart disease, cancer and diabetes pose a greater health burden worldwide than do infectious diseases, contributing to 35 million deaths annually.

This is not just a problem of the developed world. Every country that has adopted the Western diet — one dominated by low-cost, highly processed food — has witnessed rising rates of obesity and related diseases. There are now 30% more people who are obese than who are undernourished. Economic development means that the populations of low- and middle-income countries are living longer, and therefore are more susceptible to non-communicable diseases; 80% of deaths attributable to them occur in these countries.

ILLUSTRATION BY MARK SMITH

Many people think that obesity is the root cause of these diseases. But 20% of obese people have normal metabolism and will have a normal lifespan. Conversely, up to 40% of normal-weight people develop the diseases that constitute the metabolic syndrome: diabetes, hypertension, lipid problems, cardiovascular disease andnon-alcoholic fatty liver disease. Obesity is not the cause; rather, it is a marker for metabolic dysfunction, which is even more prevalent.

The UN announcement targets tobacco, alcohol and diet as the central risk factors in non-communicable disease. Two of these three — tobacco and alcohol — are regulated by governments to protect public health, leaving one of the primary culprits behind this worldwide health crisis unchecked. Of course, regulating food is more complicated — food is required, whereas tobacco and alcohol are non-essential consumables. The key question is: what aspects of the Western diet should be the focus of intervention?

In October 2011, Denmark chose to tax foods high in saturated fat, despite the fact that most medical professionals no longer believe that fat is the primary culprit. But now, the country is considering taxing sugar as well — a more plausible and defensible step. Indeed, rather than focusing on fat and salt — the current dietary 'bogeymen' of the US Department of Agriculture (USDA) and the European Food Safety Authority — we believe that attention should be turned to 'added sugar', defined as any sweetener containing the molecule fructose that is added to food in processing.

Over the past 50 years, consumption of sugar has tripled worldwide. In the United States, there is fierce controversy over the pervasive use of one particular added sugar — high-fructose corn syrup (HFCS). It is manufactured from corn syrup (glucose), processed to yield a roughly equal mixture of glucose and fructose. Most other developed countries eschew HFCS, relying on naturally occurring sucrose as an added sugar, which also consists of equal parts glucose and fructose.

Authorities consider sugar as 'empty calories' — but there is nothing empty about these calories. A growing body of scientific evidence is showing that fructose can trigger processes that lead to liver toxicity and a host of other chronic diseases1. A little is not a problem, but a lot kills — slowly (see 'Deadly effect'). If international bodies are truly concerned about public health, they must consider limiting fructose — and its main delivery vehicles, the added sugars HFCS and sucrose — which pose dangers to individuals and to society as a whole.