B vitamins (B1, B2, B3, B5, B6, B7, B9, B12) are water-soluble and involved in energy metabolism. You can buy a B complex covering the whole group or single nutrients such as B12 or B6. Vegans and older adults are often mentioned in relation to B12, but whether you need a supplement is best judged by a doctor. B vitamins can turn urine bright yellow, which is normal. Choose products that state the amount of each nutrient and show a registration number, and avoid taking several products that all contain high-dose B6.