B vitamins are a family of eight different water soluble vitamins that share similar chemistry but do very different jobs in the body. They're called a complex because they're rarely useful on their own. Take one in isolation and you can throw off the balance of the others.
The five we include in Daily Greens+ are the ones with the most everyday impact: B3 (Niacin), B5 (Pantothenic Acid), B6, B7 (Biotin) and B12. Between them, they're involved in energy metabolism, nervous system function, red blood cell formation, protein metabolism, and the health of your skin, hair and nails.
Because they're water soluble, your body doesn't store them. Anything you don't use gets flushed out. That means you need a daily intake rather than the occasional top up. And it means the bright yellow colour your urine sometimes takes on after a B vitamin is just the excess riboflavin leaving the building.
Vegans and older adults are particularly prone to running low on B12, because it's found mainly in animal foods and absorption efficiency drops with age. Niacin and B6 shortfalls show up as fatigue and irritability. Biotin issues show up first in brittle nails and dull skin.