关于营养保健品和复方维生素的功效, 在消费者心目中似乎是比较相信的, 不然不会卖得这么火爆. 这里有许多舆论宣传的功劳. 但医药界并非十分确信媒体造势所选宣传的诸多好处. 从循证医学的角度, 必须要有可靠的临床试验数据, 才能标上某种药效功能. 不然只能说未经证实和批准的疗效或个案报道.
由于替代医学越来越越被人们所接受, 那么营养保健品或部分天然产物的临床疗效自然也受到业内的关注. 最新的数据是来自对银杏叶，这是在市场上流行的，广泛用于改善记忆和其他认知功能的天然产物或营养保健品。 研究者得到美国联邦政府资助，对3000多名年龄在72-96岁的老人进行随机分布，分别采取安慰剂或120毫克的银杏抽提物做成的制剂，一天服用两次。然后进行长期观察。 研究开始时，这些受试验的老人在服用安慰剂或银杏制剂时并没有患有痴呆症。所有受试验的人都经历中位数为6年的观察。
结果发现，那些服用银杏的人在记忆，语言，注意力和认知功能等测量指标上表现得并不比那些服用安慰剂的人更好。该成果发表在本周美国医学会JAMA 杂志上。 一个更早所完成的临床研究分析还发现，银杏没有减少人们患老年痴呆症的风险。
正如今年早些时候，纽约时报专栏曾经指出，在过去几年。有大型临床研究表明，某些维生素药片和其他营养补品不改善健康方面的关键参数和结果。 一位研究过这些数据和结果的医生告诉纽约时报记者说，“我感到疑惑，为何市民普遍忽略了这种十分规范的临床试验熟结果，” “ 公众对服用维生素和营养保健品的信任度，尽管没有得到现有科学数据的支持，但是仍然无法扭转局面，义无反顾地继续服用在专业人士看来是无功效的产品。实在让人费解。政府或许没有什么可做的，因为即使是安慰剂效应，只要没有安全隐患，政府无权禁止营养保健品的畅销，这全看商家的宣传本事。
Ginkgo biloba for Preventing Cognitive Decline in Older Adults
A Randomized Trial
Beth E. Snitz, PhD; Ellen S. O’Meara, PhD; Michelle C. Carlson, PhD; Alice M. Arnold, PhD; Diane G. Ives, MPH; Stephen R. Rapp, PhD; Judith Saxton, PhD; Oscar L. Lopez, MD; Leslie O. Dunn, MPH; Kaycee M. Sink, MD; Steven T. DeKosky, MD; for the Ginkgo Evaluation of Memory (GEM) Study Investigators
JAMA. 2009;302(24):2663-2670.
ABSTRACT
Context The herbal product Ginkgo biloba is taken frequently with the intention of improving cognitive health in aging. However, evidence from adequately powered clinical trials is lacking regarding its effect on long-term cognitive functioning.
Objective To determine whether G biloba slows the rates of global or domain-specific cognitive decline in older adults.
Design, Setting, and Participants The Ginkgo Evaluation of Memory (GEM) study, a randomized, double-blind, placebo-controlled clinical trial of 3069 community-dwelling participants aged 72 to 96 years, conducted in 6 academic medical centers in the United States between 2000 and 2008, with a median follow-up of 6.1 years.
Intervention Twice-daily dose of 120-mg extract of G biloba (n = 1545) or identical-appearing placebo (n = 1524).
Main Outcome Measures Rates of change over time in the Modified Mini-Mental State Examination (3MSE), in the cognitive subscale of the Alzheimer Disease Assessment Scale (ADAS-Cog), and in neuropsychological domains of memory, attention, visual-spatial construction, language, and executive functions, based on sums of z scores of individual tests.
Results Annual rates of decline in z scores did not differ between G biloba and placebo groups in any domains, including memory (0.043; 95% confidence interval [CI], 0.034-0.051 vs 0.041; 95% CI, 0.032-0.050), attention (0.043; 95% CI, 0.037-0.050 vs 0.048; 95% CI, 0.041-0.054), visuospatial abilities (0.107; 95% CI, 0.097-0.117 vs 0.118; 95% CI, 0.108-0.128), language (0.045; 95% CI, 0.037-0.054 vs 0.041; 95% CI, 0.033-0.048), and executive functions (0.092; 95% CI, 0.086-0.099 vs 0.089; 95% CI, 0.082-0.096). For the 3MSE and ADAS-Cog, rates of change varied by baseline cognitive status (mild cognitive impairment), but there were no differences in rates of change between treatment groups (for 3MSE, P = .71; for ADAS-Cog, P = .97). There was no significant effect modification of treatment on rate of decline by age, sex, race, education, APOE*E4 allele, or baseline mild cognitive impairment (P > .05).
Conclusion Compared with placebo, the use of G biloba, 120 mg twice daily, did not result in less cognitive decline in older adults with normal cognition or with mild cognitive impairment.
Trial Registration clinicaltrials.gov Identifier: NCT00010803
