How much does taking a multivitamin help your health?

Depends on diet. In the absence of known deficiency, multivitamins are unnecessary. Common deficiencies are vitanin d in people who don't get much sun exposure and vitamin B12 in vegans who don't supplement. Multivitamins are now increasingly seen as unhealthy if not needed. Check with doctor before taking any and always check label to make sure you know what you are taking. Do not take above 100% of rda.