The defect that causes occurs within days of conception, often before the woman knows she is pregnant, therefore it is important that all women of reproductive age have adequate folate intake. Check the labels. This is an example in which the RDA is not able to keep up with research. Probably the best known vitamin and taken often as a supplement. Fortunately, vitamin C is water-soluble and readily excreted.
Toxic effects are rare.
The antioxidants are part of that protective system. When epidemiological studies are done on large population looking at nutrient intake and chronic diseases, there seems to be a firm correlation, that is, for example as vitamin E intake increases, incidence of heart disease decreases. Read lightly to realize that supplements are needed only in special cases. No need to memorize but be aware of the hazards of supplements as well as evidence that supplements of beta-carotene may increase the incidence of lung cancer in smokers. Repeat on a few other bottles if they are available.