已经过量摄入反式脂肪（trans–fatty acids，TFAs）可以增加人患心脑血管病之风险。美国疾病预防与控制中心（Centers for Disease Control and Prevention）日前公布的数据表明“与2000年比较，2009年美国白人成年人血液中的反式脂肪酸水平已经有了显著的降低”，该中心将这一变化归结于2003年通过、2006年生效的美国食品药品管理局法案，后者要求食品行业减少反式脂肪酸的添加，并应在食品标签上明确标示出反式脂肪酸的含量，及其相关方面大力开展反式脂肪有害于健康之教育等。

专家们指出，这是美国疾病预防与控制中心第一次批量测量人血液中反式脂肪酸的含量，如elaidic acid、 linoelaidic acid、 palmitelaidic acid 和 vaccenic acid 等主要反式脂肪酸均见降低。更多资讯，请参阅原文。

CDC study finds levels of trans-fatty acids in blood of U.S. white adults has decreased

Blood levels of trans–fatty acids (TFAs) in white adults in the U.S. population decreased by 58 percent from 2000 to 2009 according to a Centers for Disease Control and Prevention study published in the Feb. 8 edition of the Journal of the American Medical Association. This is the first time CDC researchers have been able to measure trans fats in human blood.

CDC researchers selected participants from the National Health and Nutrition Examination Survey (NHANES) years 2000 and 2009 to examine trans–fatty acid blood levels before and after the Food and Drug Administration′s 2003 regulation, which took effect in 2006, requiring manufacturers of food and some dietary supplements to list the amount of TFAs on the Nutrition Facts panel of the product label. During this period, some local and state health departments took steps to help consumers reduce their daily consumption by requiring restaurants to limit their use of TFAs in food and increase public awareness campaigns about the health risks associated with TFAs.

“The 58 percent decline shows substantial progress that should help lower the risk of cardiovascular disease in adults,” said Christopher Portier, Ph.D., director of CDC′s National Center for Environmental Health. “Findings from the CDC study demonstrate the effectiveness of these efforts in reducing blood TFAs and highlight that further reductions in the levels of trans fats must remain an important public health goal.”

The current study provides information for white adults only, and additional CDC studies are under way to examine blood TFAs in other adult race/ethnic groups, children, and adolescents, Dr. Portier added.

This research is a part of CDC′s larger National Biomonitoring program, which currently measures more than 450 environmental chemicals and nutritional indicators in people.

Unlike other dietary fats, trans fats are not essential to human health and do not promote good health. Research has indicated that high consumption of trans–fatty acids is linked to cardiovascular disease in part because TFAs increase LDL cholesterol (“bad” cholesterol). Changing to a diet low in TFAs may lower LDL cholesterol levels, thus decreasing the risk for cardiovascular disease.

For more information on CDC′s study: http://jama.ama-assn.org/  　

For more information on CDC′s work in the National Biomonitoring program:http://www.cdc.gov/nceh/dls/nbp.html 

Background on study　CDC studied four major TFAs to provide a reasonable representation of TFAs in blood: elaidic acid, linoelaidic acid, palmitelaidic acid, and vaccenic acid. The study measured TFAs in 229 fasting adults from the 2000 NHANES and 292 from 2009 NHANES.

The study found the overall decrease in trans–fatty acids was 58 percent. For specific trans–fatty acids, decreases were: elaidic acid – 63 percent, linoelaidic acid – 49 percent, palmitelaidic acid – 49 percent, and vaccenic acid – 56 percent.

About NHANES CDC′s National Health and Nutrition Examination is a cross–sectional survey of the U.S. population weighted to be nationally representative. For this study, researchers used a randomly selected one–half sample of white persons aged 20 years and older from the morning fasting sample from NHANES 2000 and 2009.　About Trans Fats

The USDA/HHS Dietary Guidelines for Americans 2010 recommend keeping TFA consumption as low as possible, especially by limiting foods that contain synthetic sources of trans fats, such as partially hydrogenated oils, and by limiting other solid fats:http://www.cnpp.usda.gov/DGAs2010-PolicyDocument.htm

TFAs in blood come from synthetic sources in foods, such as partially hydrogenated vegetable oils, and natural sources in foods, such as milk.

Hydrogenation is used by food manufacturers to make products containing unsaturated fatty acids solid at room temperature and therefore more resistant to becoming spoiled or rancid.

Trans–fatty acids are produced by grazing animals, and small quantities are therefore found in meat and milk products.

Since 2006, FDA has required nutrition facts labels to list the amount of trans fats in food products. At restaurants, customers can ask before they order, to know which fats are being used to prepare the food. Many restaurants display nutritional content or can provide it upon request http://www.fda.gov/Food/ResourcesForYou/Consumers/ucm079609.htm . 

CDC recommends

Look for the trans fat listing on the Nutrition Facts label. Compare brands and choose the one lowest in trans fat, preferably with no trans fat. 

Replace margarine containing trans fat with unsaturated vegetable oil. 

If you use margarine, choose a soft margarine spread instead of stick margarine. Check your labels to be sure the soft margarine does contain less trans fat. If possible, find one that says zero grams of tran fat.