Iron, zinc and magnesium nutrition and athletic performance

During the last decade there has been considerable interest in the idea that dietary trace elements supplementation can result in an improvement in athletic performance. The current paper discusses this idea as it relates to 3 elements: iron, zinc and magnesium. Emphasis has been placed on examining the implicit assumptions underlying the idea that mineral supplements help the athlete. These assumptions include the beliefs that the athlete has a higher than normal requirement for minerals; that the athlete consumes a diet inadequate in these minerals; and that a marginal deficiency of these elements has a direct effect on athletic performance. Evidence is presented that both iron deficiency and magnesium deficiency can result in a significant reduction in exercise performance; however, the biochemical lesions underlying the reductions in exercise performance have not been identified. There is evidence that dietary magnesium intake may be suboptimal in some individuals, thus dietary supplementation of this element may be useful in some population groups. Excessive magnesium supplementation is not thought to be a serious health problem. Similar to magnesium dietary iron supplements can improve athletic performance in individuals severely deficient in this element. However, few studies have documented a need for iron supplements in healthy athletes. If iron supplements are used, it is important that the level of supplementation is not excessive, as excess iron in the diet can result in an induced zinc deficiency. In marked contrast to iron and magnesium, there is little evidence for the idea that zinc deficiency influences exercise performance in humans. Despite this fact, zinc supplements have been widely advocated for the athlete, as it is known that intense exercise can result in changes in zinc metabolism. If zinc supplements are used, it is important that they are not excessive, as excess zinc in the diet can result in a secondary copper deficiency.     

Mineral and vitamin intake in field athletes (discus-, hammer-, javelin-throwers and shotputters)

Thirty field athletes (discus-, hammer-, javelin-throwers and shotputters) were studied. Dietary intake was determined by using the seven-day estimated dietary record. Analysis of the dietary intake indicated that on average, the males (n = 20) consumed adequate amounts of micro-nutrients. The mean intake for the females (n = 10) were adequate for phosphorus, zinc, vitamin A, thiamin, riboflavin, nicotinic acid, vitamin B6, folic acid, vitamin B12 and vitamin C. Some of the females did not consume adequate amounts of calcium, iron, and magnesium. These dietary deficiencies can be corrected through proper food choices and by consuming a great variety of food. Athletes (especially the females) should be educated on their nutritional needs, good dietary practices, and planning adequate diets for training and performance.     

Zinc: an essential trace element with potential benefits to soldiers

Zinc is a trace element known to be an essential nutrient for life. It functions as a cofactor for numerous enzymes, including those involved in DNA and RNA replication and protein synthesis. Soldiers represent a unique population faced with intense metabolic and mental demands, as well as exposure to various immune challenges. Some of these factors may affect their dietary zinc requirements. Although severe zinc deficiency is unlikely to occur, some soldiers may experience less than optimal zinc status because of diminished intake coupled with increased requirements. For those soldiers, supplemental dietary zinc may serve a protective function in numerous disease states affecting modern warfighters. This review highlights the importance of adequate zinc nutriture to soldiers and discusses the potential benefits of supplemental zinc in a number of diseases currently affecting soldiers, including diarrhea, respiratory diseases, malaria, and leishmaniasis.     

Effects of aerobic exercise and training on the trace minerals chromium, zinc and copper

Aerobic exercise and training lead to numerous changes and/or adaptations in the normal physiological functioning of the body. The trace minerals chromium, zinc, and copper are directly involved in maintaining and regulating many of these physiological processes, especially those involved in normal carbohydrate, fat and protein metabolism and the ultimate formation of usable energy. Therefore, it is important to establish whether exercise and training alter the functions of these trace elements, and to determine the overall effects of exercise on nutritional status and physical performance. Exercise results in a marked mobilisation of chromium into circulation, while zinc and copper levels have been shown to either remain stable or increase. Exercise also results in large increases in excretion of chromium, zinc and copper. Urinary chromium excretion has been shown to increase on an exercise day compared with a rest day, while increased zinc losses occur in urine and sweat and increased copper losses occur in urine, and faeces. When exercise-enhanced trace mineral losses are coupled with dietary intakes below the recommended levels, which are commonplace for both sedentary and exercising individuals, the nutritional status and overall health of exercising individuals may be suboptimal. Individuals who train intensively may be at special risk due to repeated increased losses. Trained athletes have lower resting urinary chromium losses, larger increases in urinary chromium losses due to exercise, lower resting serum zinc levels, and possible alterations in copper nutriture compared with sedentary controls. These changes suggest an altered metabolism and/or nutritional status of the trace minerals chromium, zinc, and copper in trained individuals and those who exercise strenuously.     

Nutrition survey in elite rhythmic gymnasts

BACKGROUND: Young female rhythmic gymnasts have been identified as a potential risk group for malnutrition because of their attitude of weight reduction and leanness. METHODS: This study aimed to assess the dietary practices of 20 rhythmic gymnasts of the Italian national team, on the basis of a three-day food records collected by clinical interview. Twenty-four age-matched non-athletic females served as controls. RESULTS: The reported energy intake was similar in gymnasts and controls (28.5+/-5.6 vs 28.2+/-7.8 kcal/kg b.w., per day), but less than the recommended and the estimated requirements. Energy intake from carbohydrates was higher (53+/-6 vs 49+/-6%, p<0.05) and that from lipids lower (31+/-6 vs 34+/-4%, p<0.05) in gymnasts than in controls. In the former the energy supply from breakfast was higher (24+/-2 vs 16+/-4%, p<0.001) and from snacks was lower (8+/-9 vs 17+/-10%, p<0.01). Gymnasts also distinguished from controls for lower cholesterol and saturated fatty acid intake, and for higher fibre (14+/-5 vs 9+/-2 g/1,000 kcal, p<0.001) and Vitamin A dietary content. Calcium, iron and zinc intake were less than 100% RDA in both groups. CONCLUSIONS: In some ways, dietary practices of rhythmic gymnasts meet nutritional recommendations more than those of non athletic controls, though discrepancy between reported energy intake and estimated energy requirement exists. Suboptimal calcium, iron and zinc intake were observed both in gymnasts and in controls, hence minerals supplementation could be required. The dietary attitude could be regarded as a positive aspect of rhythmic gymnastics, provided athletes, physicians and coaches correct dietary errors and avoid excessive food restrictions.     

消防官兵营养状况调查及相应对策研究

 目的 分析消防官兵膳食营养和健康状况,并提出卫生勤务对策,为改善后勤保障提供科学依据。方法 采用连续3 d称重法对296 名消防官兵的膳食和营养素的摄入情况进行了调查,并分析其膳食营养情况,以提出针对性卫生勤务对策。结果 本次调查的消防官兵谷薯类、禽畜类、蔬菜、水果、鱼虾类、蛋类、奶类、豆类等食物摄入偏低,食用油、盐类摄入偏高;糖类(51.4%)和蛋白质(12.5%)供能比例合理,但脂肪供能比例偏高(36.1%)。维生素A、硫胺素、核黄素、烟酸、钙和锌摄入不达标。结论 该武警部队消防官兵群体存在膳食结构不合理,营养素摄入不足和摄入不均衡现象,下一步应加强卫生勤务保障工作。     

Changes in plasma lipoprotein levels during a hiking expedition in South America.

Eleven males participated in a hiking expedition over a period of 6 weeks during which they walked an average of 15 km per day, resting days included. The participants completed a seven-day estimated dietary record before and during the expedition. Their habitual dietary intake before the expedition was typical of a Western diet. During the expedition most animal products, with the exception of canned fish, were excluded from the diet. The dietary intake of fat and carbohydrate changed from 36.9% and 40.6% to 14.0% and 76.4% respectively. Cholesterol intake dropped from 557 mg to 92 mg. Mean plasma total cholesterol (TC) decreased from 190.9 mg/100 ml to 142.0 mg/100 ml. These changes were mainly due to changes in low density lipoprotein cholesterol (LDL-C). Although high density lipoprotein cholesterol (HDL-C) did not change, the ratio of HDL-C to TC increased significantly. It can be concluded that drastic dietary changes, together with increased physical activity and weight loss resulted in major plasma lipoprotein changes. The expected fall in HDL-C due to a high carbohydrate diet was counteracted by the increased physical activity and weight loss.     

睾酮对大鼠肝脏金属硫蛋白诱导合成的作用

本研究主要观察了睾酮对大鼠肝脏金属硫蛋白(Metallothionein,MT)诱导合成的作用,并动态观察了不同锌营养状态的大鼠在急性力竭运动后的恢复期中,肝脏金属硫蛋白诱导合成和锌、铜、铁离子含量的变化,探讨了它们之间的关系.结果显示大鼠皮下注射睾酮能够刺激诱导肝脏MT的合成.锌缺乏引起安静状态下大鼠肝脏MT含量下降,MT下降的原因可能与睾酮低下和锌离子减少有关.睾酮可能是MT在体内的正向调节因子.营养性锌缺乏不仅引起大鼠肝脏MT和锌基础水平的下降,而且导致急性力竭游泳后肝脏MT峰值较晚出现.这表明锌缺乏造成MT对运动的应激能力和合成速率下降,这将不利于运动后自由基的清除和组织的恢复.不管大鼠的锌营养状态如何,力竭游泳后,肝脏锌、铜、铁的含量均出现不同程度的升高或升高趋势.这些金属离子的升高和再分布,可能与MT的升高有关.     

Reversing Sports-Related Iron and Zinc Deficiencies

In brief Many active patients, particularly brief gymnasts, ballet dancers, wrestlers, and long-distance runners, do not consume enough iron or zinc. Iron and zinc are important for oxygen activation, electron transport, and injury healing. Subclinical deficiencies may impair athletic performance and prolong healing times. People who compete or exercise regularly should be counseled about the importance of these minerals and how to ensure adequate dietary intake.     

缺锌对运动训练大鼠血清和睾丸睾酮及锌水平的影响

为探讨缺锌对运动能力影响的机制，本研究通过建立大鼠缺锌模型和跑台训练模型，观察缺锌对运动训练大鼠血清和睾丸睾酮及锌水平的影响。结果显示：缺锌引起训练和未训练大鼠体重、身长增长缓慢，身体瘦弱，跑台训练及运动中，主动性差，不愿奔跑，表现出缺锌对运动意识和能力的影响。锌缺乏大鼠血清和睾丸睾酮及锌含量显著下降（Ｐ＜０．０５）。运动训练引起锌缺乏大鼠睾丸重量减少（Ｐ＜０．０５）。７５％ＶＯ＿（２ｍａｘ）强度运动后即刻，锌充足大鼠血清锌水平显著上升，而锌缺乏大鼠血清锌显著下降（Ｐ＜０．０５）。结果表明，缺锌引起机体睾酮水平下降，可能籍此影响运动能力。缺锌状况下训练将加速睾丸的萎缩。运动后血清锌的变化与机体锌营养状况有关。     

Zinc as an antiperoxidative agent following iodine-131 induced changes on the antioxidant system and on the morphology of red blood cells in rats

Iodine-131 ((131)I) irradiation is the first line treatment for Graves' disease and thyroid carcinoma. In such cases, (131)I gets accumulated in the thyroid, and is released in the form of radioiodinated triiodothyronine (T3) and tetraiodothronine (T4). Various reports describe changes in the blood picture after radioiodine treatment. Zinc, on the other hand, has been reported to maintain the integrity of red blood cells (RBC) under certain toxic conditions. The present study was conducted to evaluate the adverse effects of (131)I on the antioxidant defense system and morphology of RBC and also to assess the possible protection by zinc under irradiation by (131)I. Thirty two female Wistar rats were equally segregated into four main groups. Animals with Group I served as normal controls; Group II animals were administered a dose of 3.7 MBq of (131)I (carrier free) intraperitoneally, Group III rats were supplemented with zinc (227 mg/L drinking water) and Group IV rats were given a combined treatment of (131)I and zinc, in a similar way as in Group II and IV rats. After seven days of (131)I treatment, RBC lysate was prepared and its antioxidant status assessed. The activity of superoxide dismutase (SOD), reduced glutathione (GSH) and malondialdehyde (MDA) in the lysate of RBC was increased. On the contrary, the activity of catalase was found to be significantly decreased. The activity of glutathione reductase (GR) remained unchanged. Marked changes in the shape of RBC from normal discocytes to echinocytes, spherocytes, stomatocytes and acanthocytes were also observed in the blood of the rats treated with (131)I. Zinc supplementation to (131)I treated rats, significantly attenuated the adverse effects caused by (131)I on the levels of MDA, GSH, SOD and catalase. In conclusion, the study revealed significant oxidant/antioxidant changes in RBC following (131)I administration in rats, while zinc was shown to act as a radioprotector agent.     

Nutritional evaluation of a sailing crew during a transatlantic race

Few studies describe the nutritional status of people in stressful situations and with limited access to food. We assessed the dietary intake and serum indices of nutritional status in a sailing crew ( n = 14) during a transatlantic race and in a control group ( n = 11 males). The crew's mean energy intake was 13.3 MJ/d. In both groups, the intake of retinol, thiamin, riboflavin, vitamin C, calcium and iron was sufficient but the intake of vitamin B₆, magnesium and zinc rather low. In sailors, serum HDL cholesterol was higher before the race (1.61 mmol/l; 95% confidence interval: 1.44–1.69) than after it (1.34 mmol/l; 1.26–1.43). Serum calcium, potassium, magnesium, ferritin, zinc, and selenium concentrations did not indicate nutritional deficiency in either group.     

Diet composition, energy intake, and nutritional status in relation to obesity in men and women

There are dietary factors besides the total energy value of food that can affect adiposity by disrupting the balance between energy intake and expenditure. The purpose of this paper was to examine how perturbation of these dietary factors that control energy balance affects adiposity. There is a substantial amount of evidence suggesting that obesity is not associated with overeating, but with a high dietary fat-to-carbohydrate intake ratio. Physiological adaptations to energy-reduced dieting facilitate both weight regain and make it more difficult to lose weight during subsequent dieting attempts. Since obesity may be better characterized by diet composition than by energy intake, successful weight-loss programs should include diet compositional changes in their regimes.     

缺Zn对幼年大鼠Zn代谢及脑发育的影响

 采用缺Zn液体饲料灌胃方法复制出单纯缺Zn模型(PZD),发现缺Zn 14 d后,PZD组大鼠血清Zn浓度、AKP活力显著下降,脑、海马Zn浓度和脑蛋白浓度未发生明显变化,提示在缺Zn早期,脑组织对Zn代谢调节较为稳定.     

高原边防部队膳食营养调查分析

目的 了解高原边防部队膳食营养现状,为高原部队食物及营养素推荐摄入量标准的制定提供依据.方法 采用GJB 1636A-2016中称重法和体格检查法对驻海拔4600 m(A部)和4030 m(B部)单位的膳食营养情况进行调查.按GJB826B-2010和GJB823B-2016进行膳食质量评价;高效液相色谱法检测血浆维生素A含量,ELISA法检测血浆25-OH VD含量;上臂肌围采用GJB1636A-2016评价,体脂率采用体成分仪所附标准评价.结果 A部禽蛋、牛奶和植物油摄入达标,其余食物未达标;B部粮食和植物油摄入达标,其余食物摄入未达标.A部蛋白质、钙、磷、钠、铁、硒、碘、铜、锰、维生素E、B3摄入充足,能量、钾、锌、镁、维生素D、C、B1和B2摄入不足,维生素A、B6、B9和B12严重缺乏;B部能量、蛋白质、磷、钾、钠、锌、铁、硒、镁、铜、锰、维生素E、C、B1和B3摄入充足,维生素B2摄入不足,钙、碘、维生素A、D、B6、B9和B12严重缺乏.A部蛋白质和脂肪产热达标,碳水化合物产热过低;B部蛋白质产热达标,脂肪产热超标,碳水化合物产热过低.两单位人员血浆维生素A含量充足;血浆25-OH 维生素D含量不足及缺乏.A部和B部上臂肌围正常人数比分别为93.5%和97.7%,体脂率偏瘦人数比分别为80.6%和70.5%.结论 高原边防部队的食物和营养素摄入不均衡,机体维生素D缺乏,但蛋白质营养状况较好,体脂较低,还需调整膳食结构和进行营养宣教来改善高原部队膳食营养现状.     

Training effects on blood zinc levels in humans

Effects of physical training on fasting erythrocyte and plasma zinc distributions were studied on seven previously sedentary male students. The training consisted of running over 5 km, 6 times/week for 10 weeks. Maximum aerobic capacity (VO2max) and 12 min walk-run performance increased significantly (p less than 0.01) after training. The erythrocyte concentrations of total zinc and of zinc derived from carbonic anhydrase I (CA-I) rose significantly (p less than 0.05) after training, whereas no such effects were noted in CA-II-derived zinc, Cu2Zn2 superoxide dismutase-derived zinc, and other zinc. On the other hand, no effect of training was found in total or alpha 2-macroglobulin-bound zinc in plasma, although albumin-bound zinc concentration declined significantly (p less than 0.05). Following the training period, however, the response to a VO2max test of the van Beaumont quotient (J Appl Physiol 1973;34:102-6) for total plasma zinc had decreased significantly (p less than 0.05), suggesting a relative reduction of the circulating exchangeable zinc. In addition, there were significant (p less than 0.05) decreases in plasma iron and ferritin concentrations after training, indicating latent iron deficiency anemia. These results may suggest that the changes in CA-I-derived zinc and/or albumin-bound zinc portend zinc deficiency during running training and that sports anemia precedes hypozincemia in athletes.     

武警某机动部队官兵膳食营养调查

 目的 了解武警某机动部队官兵的膳食结构和营养状况,为指导其合理膳食提供参考。方法 选取某机动部队共514名官兵作为调查对象,采用称重法进行连续4 d的膳食调查,计算能量及营养素摄入情况,了解官兵的营养缺乏状况,采取体格检查和问卷调查的方式评估官兵的膳食结构和营养状况。结果 机动部队一类灶和二类灶官兵日人均能量摄入量符合军标,三类灶官兵日人均能量摄入量低于军标。一类灶官兵畜肉、鱼虾、大豆、蔗糖和干菜等摄入量低于军标,钠和维生素D摄入量低于军标;二类灶官兵鱼虾、大豆、蔗糖、食用菌、干菜和饮料等低于军标,磷、锌、硒和维生素D、E、B₁、B₂、B₆、C以及烟酸低于军标;三类灶官兵水果、鱼虾、牛奶、豆类等低于军标,钾、钙、磷、铁、锌、硒和维生素A、B₁、B₂、B₆以及维生素C低于军标。体格检查发现二类灶中有44.45%的官兵体质指数和体脂异常,问卷调查显示45.04%的官兵训练后感到疲乏和睡眠不好。结论 某机动部队官兵存在膳食结构不合理、供能比例不合理的情况。建议增加多种类型果蔬、鱼虾的摄入,适当减少动物性油脂的摄入。     

耐力性运动对锌、铜代谢的影响

本文的研究提示运动员经历一次马拉松比赛及长期高强度冬季系统训练后可以导致血清锌、铜水平及尿锌、铜排出量的改变。大白鼠一次衰竭性游泳运动试验也证实,运动可以导致肝脏、肌肉中的锌、铜含量呈增加趋势。     

Subchronic exposure to static magnetic field differently affects zinc and copper content in murine organs

Purpose Static magnetic fields (SMF) have been widely used in research, medicine and industry. Since zinc and copper play an important role in biological systems, we studied the effects of the subchronic continuous SMF exposure on their distribution in murine tissues.

Materials and methods For 30 days, mice were exposed to inhomogeneous, vertical, downward or upward oriented SMF of 1?mT averaged intensity with spatial gradient in vertical direction.

Results SMF decreased the amount of copper and zinc in liver. In brain, zinc levels were increased and copper levels were decreased. In spleen, zinc content was reduced, while copper amount remained unchanged.

Conclusions Subchronic exposure to SMF differently affected copper and zinc content in examined organs, and the changes were more pronounced for the downward oriented field. The outcome could be attributed to the protective, rather than the harmful effect of SMF.     

Protection against ionising radiation and synergism with thiols by zinc aspartate

Pre-treatment with zinc aspartate protected mice against the lethal effects of radiation and raised the LD50 from 8 Gy to 12.2 Gy. Zinc chloride and zinc sulphate were clearly less active. The radioprotective effect of zinc aspartate was equivalent to cysteamine and slightly inferior to S,2-aminoethylisothiourea (AET). Zinc aspartate displayed a similar therapeutic index to the thiols but could be applied at an earlier time before irradiation. Synergistic effects occurred with the combined administration of zinc aspartate and thiols. By giving zinc aspartate with cysteamine, the LD50 was increased to 13.25 Gy and, by combining it in the optimal protocol with AET, to 17.3 Gy. The radioprotection by zinc and its synergism with thiols is explained by the stabilisation of thiols through the formation of zinc complexes.