Any comments concerning specific vitamin levels must be treated with respectful caution . 对于任何有关某种维生素给量的建议都必须十分谨慎。
Certain species of seaweed have been reported to contain appreciable quantities of vitamin b12 . 曾有报道某些种海藻含有相当量的维生素B12。
Many agents such as vitamin a, some steroids, and some drugs are membrane-active . 很多药物，如维生素A、某些类固醇以及某些药是“膜活性的”。
Vitamin d is the only vitamin, apart from nicotinic acid, that is synthesized in the body . 除烟酸以外，维生素D是唯一的在人体里合成的维生素。
Vitamins are very potent organic substances that occur in minute quantities in natural foodstuffs . 维生素是以微量形式存在于天然食物中的非常有用的有机物。
The water-soluble vitamins, embracing the b complex and vitamin c, are important for animal metabolism . 包括维生素B族和维生素C在内的水溶性维生素对动物代谢是重要的。
These effects can be overcome by addition of vitamin e and an effective antioxidant, such as ethoxyquin . 这些作用可用加入维生素E和有效的抗氧剂，如乙氧喹啉，来加以克服。
The vitamin b12 requirements appear to depend upon the levels of choline, methionine and folic acid in the diet . 维生素B12的需要量决定于食品中胆碱、蛋氨酸以及叶酸的含量。
vitamin is widely distributed in foods of animal origin such as meat, milk, eggs, fish and shellfish. 维生素广泛分布于动物来源的食物中，如肉、奶、蛋、鱼和贝类。
This practice can lead to excess levels since little reliance is placed on the natural vitamin content of feedstuffs . 这种实践结果，由于很少注意饲料中天然的维生素含量，就能出现含量过多的问题。
