恶性肿瘤对人类健康的危害程度日趋严重,给患者个人、家庭和社会在精神上、肉体上和经济上都造成极其沉重的负担。即使像美国那样的发达国家也感到承受不了日益增长的医疗保险费用。从尼克松的“战胜癌症倡议”到后来的“降低癌症死亡50％”的计划均未取得预期的效果。肿瘤发病率仍在逐年增长,肿瘤死亡亦未见下降,尤其是肺癌死亡的增长抵消和超过了近几十年中其它肿瘤死亡的下降。严峻的事实促使美国科学家和政府开始重视恶性肿瘤的预防工作。80年代美国科学家在政府支持下进行了3个旨在预防吸烟者发生肺癌的大规模长期人群干预试验,被试者近10万人,历时近10年。结果却出乎意料:在芬兰进行的试验表明服用其营养素组患肺癌的人数反而比对照组增加了18％。其它两个在美国本土进行的类似实验也因情况不妙而提前结束。美国政府为这3个试验已经花费近1亿美元。 Malignant tumors have become more and more serious to human health, and cause an extremely heavy burden on patients, individuals, families and society mentally, physically and economically. Even developed countries like the United States are not able to afford the ever-increasing cost of health insurance. From Nixon’s “Conquering Cancer Initiative” to the later “Reducing cancer deaths by 50%,” the plan has not achieved the desired results. The incidence of tumors is still increasing year by year, and tumor death has not been reduced. In particular, the increase in deaths from lung cancer offsets and exceeds the decline in deaths from other tumors in recent decades. The grim facts prompted American scientists and the government to pay attention to the prevention of malignant tumors. In the 1980s, American scientists conducted three large-scale long-term crowd-intervention trials aimed at preventing lung cancer among smokers with government support. Nearly 100,000 people took the test, which lasted nearly 10 years. The results were unexpected: Tests conducted in Finland showed that the number of patients who received lung cancer in their nutrient group was 18% more than that in the control group. The other two similar experiments conducted in the United States ended prematurely due to unfavorable conditions. The U.S. government has spent nearly $100 million for these three tests.