Department of Family and Community Medicine, Medical University of Lodz, Lodz, Poland.
J Am Coll Nutr. 2010 Aug;29(4):397-406. doi: 10.1080/07315724.2010.10719857.
To determine whether (1) rapid consumption of 1 L of apple juice increases blood antioxidant capacity, measured as ferric-reducing ability of plasma (FRAP) and serum 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity, and (2) apple polyphenols or fructose-induced elevation of plasma uric acid contributes to post-juice increase of blood antioxidant activity.
The study involved 12 (mean age 32 ± 5 years, mean body weight 73 ± 7 kg) healthy nonsmoking subjects. Tested subjects consumed 1 L of clear apple juice and then FRAP; serum DPPH-scavenging activity, serum uric acid, and total plasma phenolics and quercetin levels were measured just before juice ingestion and 1, 2.5, and 4 hours after ingestion. This was repeated 3 times with 4-day intervals, but volunteers drank either 1 L of clear apple juice without polyphenols (placebo), or 1 L of cloudy apple juice (positive control), or 1 L of water (negative control) at the time. All juices had similar content of sugars (i.e., saccharose, glucose, and fructose) and precisely defined composition of phenolics and antioxidant activity.
Consumption of all 3 juices transiently increased FRAP and serum DPPH-scavenging activity, with peak values at 1 hour post-juice ingestion. This was paralleled by the rise of serum uric acid, but no significant changes in plasma total phenolics and quercetin levels were observed after all dietary interventions. At the same time, no substantial differences were found between juices (especially between clear apple juice and clear apple juice without polyphenols) concerning the measured variables. A strong significant correlation was noted instead between serum uric acid and plasma antioxidant activity at all analyzed time points, before and after juice ingestion. Plasma total phenolics and quercetin levels were not associated with FRAP and serum DPPH radical-scavenging activity.
We have demonstrated that rapid consumption of apple juice increased plasma antioxidant activity in healthy subjects; this was caused by the fructose-induced rise of serum uric acid levels, but was not due to the presence of antioxidant polyphenols in juice. Thus, short-term consumption of apple juice seems not to be the effective dietary intervention to augment plasma antioxidant activity due to the concomitant possibility for uric acid to be a risk factor for several diseases, as verified by other authors.
确定（1）快速饮用 1 升苹果汁是否会增加血液抗氧化能力，用血浆还原能力（FRAP）和血清 2,2-二苯基-1-苦基肼（DPPH）自由基清除活性来衡量，以及（2）苹果多酚或果糖诱导的血尿酸升高是否有助于果汁饮用后血液抗氧化活性的增加。
本研究纳入了 12 名（平均年龄 32 ± 5 岁，平均体重 73 ± 7kg）健康不吸烟的受试者。测试对象饮用 1 升澄清苹果汁，然后测定 FRAP；在饮用果汁前、饮用后 1、2.5 和 4 小时测定血清 DPPH 清除活性、血清尿酸、总血浆酚类和槲皮素水平。这 3 次实验之间间隔 4 天，志愿者在同一时间分别饮用 1 升澄清无多酚苹果汁（安慰剂）、1 升混浊苹果汁（阳性对照）或 1 升水（阴性对照）。所有果汁的糖含量（即蔗糖、葡萄糖和果糖）相似，酚类和抗氧化活性的组成也完全相同。
饮用所有 3 种果汁均短暂增加了 FRAP 和血清 DPPH 清除活性，峰值出现在果汁饮用后 1 小时。同时，血清尿酸升高，但在所有饮食干预后，血浆总酚类和槲皮素水平没有明显变化。与此同时，在测量的变量方面，果汁之间（特别是澄清苹果汁和澄清无多酚苹果汁之间）没有发现明显差异。相反，在所有分析时间点，包括果汁饮用前后，都观察到血清尿酸和血浆抗氧化活性之间存在显著的正相关。血浆总酚类和槲皮素水平与 FRAP 和血清 DPPH 自由基清除活性无关。
我们已经证明，在健康受试者中，快速饮用苹果汁可增加血浆抗氧化活性；这是由果糖诱导的血清尿酸水平升高引起的，但不是由于果汁中存在抗氧化多酚。因此，短期饮用苹果汁似乎不能有效干预来增加血浆抗氧化活性，因为尿酸可能是其他作者验证的多种疾病的危险因素。
