紫皮土豆
研究首次证实土豆对血压的影响，结论是：每天食用2小份紫色土豆（Purple Majesty）能降低血压约4%，而且不会增加体重。在JAFC杂志的报道中，研究人员称，4%的降低看似很小，但足以减少潜在患数种心脏疾病的风险。
Joe Vinson和他的同事们指出，美国人吃土豆多过其他任何蔬菜。紫皮土豆（一种精品品种，以含有高水平抗氧化物质而闻名）越来越多地在食品商店出售。在韩国，紫色土豆是一种用于减肥的著名民间医药。Vison的团队因而决定在18位志愿者（大多都超重而且有高血压）身上开展调查研究，每天2次吃6-8个微波烹制的小土豆。这些志愿者连续4周吃或不吃土豆，随后交换组别再进行4周，同时研究人员对志愿者的舒张压和收缩压、体重及其他健康指标进行监测。
结果显示，平均舒张压下降了4.3%，收缩压下降了3.5%。大部分受试者服用抗高血压药，但血压仍有降低。研究的参与者们都没有体重的增加。Vinson说，其他研究已经在土豆中鉴定出与知名的ACE-抑制剂药物（一种重要的治疗高血压的药物）有相似功能的物质。但他怀疑，这些作用可能是由于土豆中其他的物质所致。目前科学家还不清楚普通的白土豆是否也有相似的有益作用。
High antioxidant potatoes: Acute in vivo antioxidant source and hypotensive agent in humans after supplementation to hypertensive subjects
Joe A. Vinson, Cheryil A Demkosksy, Duroy A Navarre, and Melissa A Smyda
Potatoes have the highest daily per capita consumption of all the vegetables in the US diet. Pigmented potatoes contain high concentrations of antioxidants, including phenolic acids, anthocyanins, and carotenoids. In a single dose study we gave 6-8 microwaved potatoes with skins or a comparable amount of refined starch as cooked biscuits to 8 normal fasting subjects and took repeated samples of blood over an 8-hour period. Plasma antioxidant capacity was measured by Ferric Reducing Antioxidant Power (FRAP). A 24-hour urine was taken before and after each regimen. Urine antioxidant capacity due to polyphenol was measured by Folin reagent after correction for non-phenolic interferences with a solid phase (Polyclar) procedure. Potato caused an increase in plasma and urine antioxidant capacity whereas refined potato starch caused a decrease in both, i.e. was a pro-oxidant. In a crossover study 18 hypertensive subjects with an average BMI of 29 were given either 6-8 small microwaved purple potatoes twice daily or no potatoes for 4 weeks and then given the other regimen for another 4 weeks. There was no significant effect of potato on fasting plasma glucose, lipids, HbA1c. There was no significant body weight increase. Diastolic blood pressure significantly decreased 4.3%, a 4 mm reduction. Systolic blood pressure decreased 3.5%, a 5 mm reduction. This blood pressure drop occurred in spite of the fact that 14/18 subjects were taking antihypertensive drugs. This is the first study to investigate the effect of potatoes on blood pressure. Thus purple potatoes are an effective hypotensive agent and lower the risk of heart disease and stroke in hypertensive subjects without weight gain.
