Comparison of a vitamin E-rich diet and supplemental vitamin E on measures of vitamin E status and lipoprotein profile

OBJECTIVE: To determine whether dietary modification rather than use of supplements can raise indices of vitamin E status to potentially cardioprotective levels. DESIGN: Eight week randomised controlled trial with parallel treatments to compare increased use of vitamin E-rich foods, supplementation with 200 IU of vitamin E, and a placebo. SETTING: Dunedin, New Zealand. SUBJECTS: Ninety subjects were recruited, of whom 82 non-smoking, free-living individuals aged 22-72 y with plasma cholesterol <7.5 mmol/l completed the trial. MAIN OUTCOME MEASURES: Dietary intakes, plasma alpha tocopherol, plasma alpha tocopherol/cholesterol ratio and lipoprotein cholesterol. RESULTS: Consumption of an additional 12 mg of vitamin E (alpha tocopherol equivalents) from dietary sources was primarily achieved through the replacement of saturated fat-rich foods with unsaturated fats rich in vitamin E, nuts and vegetables. This resulted in a 3.4 micromol/l increase in plasma alpha tocopherol at week 6 (95% CI 1.6-5.3), and 0.9 micromol/mmol in plasma alpha tocopherol/cholesterol at weeks 4 and 6 (95% CI 0.3-1.4 and 0.4-1.4, respectively) when compared with the placebo group. In the supplement group, plasma alpha tocopherol and plasma alpha tocopherol/cholesterol were significantly increased within 2 weeks and remained so throughout the 8 week intervention. CONCLUSION: Increasing dietary vitamin E intake can increase plasma alpha tocopherol levels, although factors other than dietary intake are also important determinants. The extent of dietary modification required to achieve potentially cardioprotective levels of plasma alpha tocopherol is difficult in practice. SPONSORSHIP: The study was supported through the Otago Medical Research Foundation Laurenson Award.     

Maternal vitamin D status: effect on milk vitamin D content and vitamin D status of breastfeeding infants

There are increasing reports of rickets and vitamin D deficiency worldwide. Breastfeeding without adequate sunlight exposure and vitamin D supplementation are the major risk factors. In view of the drive to promote and increase the rate of exclusive breastfeeding, the relationship among maternal vitamin D status, vitamin D concentration of human milk, and hence vitamin D status of breastfeeding infants deserves reassessment. This review provides current information on the interrelationship between maternal vitamin D status and the vitamin D status of the breastfeeding infant. It also reviews the results of ongoing research on the effect of high-dose maternal vitamin D supplementation alone as a possible option to prevent vitamin D deficiency in the breastfeeding mother-infant dyad.     

Safety of vitamin A

Vitamin A adequacy is discussed in terms of the recommended allowances appropriate for the needs of the majority of individuals. Deficiency can result in xerophthalmia and permanent blindness and in increased mortality rates among children. Toxicity has been associated with the overconsumption of vitamin A supplements. Acute hypervitaminosis A may occur after ingestion of greater than or equal to 500,000 IU (over 100 times the RDA) by adults or proportionately less by children. Symptoms are usually reversible on cessation of overdosing. Factors influencing chronic hypervitaminosis A include dosing regimen, physical form of the vitamin, general health status, dietary factors such as ethanol and protein intake, and interactions with vitamins C, D, E, and K. Both excess and deficiency of vitamin A in pregnant animals was shown to be teratogenic. In humans, congenital malformations associated with maternal over-use of high doses of vitamin A were reported but no cause-and-effect relationship has been established. Deficiency of the vitamin during pregnancy has also been associated with congenital abnormalities. Reported incidences of vitamin A toxicity are rare and have averaged fewer than 10 cases per year from 1976 to 1987.     

Relationships between vitamin A and vitamin E in the chick

Plasma levels of vitamins A and E were analysed during the dietary administration of two levels of vitamin A (10 000 or 50 000 IU/kg) in combination with four levels of supplemental vitamin E (0, 50, 100, or 150 mg/kg) and with or without a supplement of oil to the diet. Tocopherol levels in plasma were markedly decreased by the higher vitamin A supplementation. In contrast, the various vitamin E intakes had no influence on plasma retinol levels. The addition of oil to the diet did not affect this interaction. The absorption, distribution and elimination of labeled 3H-dl-alpha-tocopheryl acetate after an oral or intravenous administration, in combination with a high oral dose of vitamin A (100 000 IU/chick), were studied. The high oral single dose of vitamin A reduced the levels of radioactivity in all the analysed tissues and organs, when both vitamins were administered orally. However, vitamin A did not affect distribution and elimination of radioactivity, when an interaction in the gastro-intestinal tract was avoided by different routes of administration.     

老年人血浆维生素K和D水平的季节变化

目的了解老年人群血浆维生素K和维生素D水平的季节变化。方法对85名健康老年人用放射免疫分析法测定春秋两季血浆维生素D(25(OH)D)和甲状旁腺素(PTH)含量,用高压液相色谱法测定血浆维生素K含量。结果血浆维生素K水平女性在春秋两季均明显高于男性,而男性和女性各自无季节性差异。无论男女秋季血浆维生素(25(OH)D)水平明显高于春季,同一季节内男女间差异无统计学意义。维生素D缺乏率女性春季为63.4%,秋季为7.3%。男性春季为65.9%,秋季无缺乏者。春季维生素D缺乏率显著高于秋季(P<0.05)。男女秋季血浆PTH浓度明显低于春季。老年女性春季血浆25(OH)D浓度和血浆PTH浓度之间呈负相关(r=-0.426,P<0.001)。结论该人群血浆25(OH)D和PTH有明显的季节变化,春季血浆25(OH)D水平低。而血浆维生素K没有季节变化。     

Glucose tolerance and vitamin D: effects of treating vitamin D deficiency

OBJECTIVE: We investigated the effects of vitamin D treatment on plasma glucose, serum insulin, and insulin sensitivity in vitamin D-deficient individuals without diabetes mellitus. METHODS: Thirty-three adults with vitamin D insufficiency (serum 25-hydroxyvitamin D concentration 相似文献   

Influence of excess vitamin E on vitamin A toxicity in rats.

Male Holtzman rats (78 g) were fed semipurified 16% protein diets for 8 weeks using a food grade soy protein concentrate as the protein source. The basal diet (A) contained added DL-methionine (0.26%) and adequate amounts of vitamins A (14,535 IU/kg as retinyl acetate) and E (60 IU/kg as DL-alpha-tocopheryl acetate) and all other required nutrients. Experimental diets included: (B) basal plus 600 IU of vitamin E/kg; (C) basal plus 6,000 IU of vitamin E/kg; (D) basal plus 2.9 X 10(6) IU of vitamin A/kg; (E) basal plus 2.9 X 10(6) IU of vitamin A plus 600 IU of vitamin E/kg; and (F) basal plus 2.9 X 10(6) IU of vitamin A plus 6,000 IU of vitamin E/kg. Both vitamin A and vitamin E had a significant (P less than 0.05) effect on growth. There was an increase in growth with vitamin E intake and a decrease in growth with vitamin A intake. The net result of these two effects was that the groups fed both vitamins tended to be quite close in mean values to the group fed only the basal diet. Vitamin A significantly (P less than 0.05) increased relative weights of spleen and testes; vitamin E reduced that effect. Vitamin E also significantly (P less than 0.05) reduced relative adrenal weight whereas vitamin A significantly increased it. The two effects tend to cancel each other in the sense that the group fed both vitamins had an average relative adrenal weight quite close to that of the group fed only the basal diet. However, vitamin A still had an effect even when 6,000 IU of vitamin E was fed. The interaction effect of the two vitamins was significant (P less than 0.05) for plasma total protein and liver vitamin A. There was an increase in liver vitamin A with increasing levels of vitamin E in the diet. Blood urea nitrogen and plasma cholesterol were unchanged. A significant interaction of vitamins A and E was found to effect plasma total protein, liver vitamin A, and relative weight of spleen and testes.