Pharmacist here. Multivitamins are not bad per se, but taking more than the recommended dosage is (like others have already commented!). For most multivitamins, that’s just 1 pill a day. Most vitamins are water-soluble and you’ll just pee out any excess. If you are already eating a clean and healthy diet, you really don’t need a multivitamin. They’re meant to supplement your diet, not replace.
Some of the trace elements/minerals included in a multivitamin are not recommended to double-up on. You’re body doesn’t need a whole lot of selenium, chromium and so forth.
If your boyfriend is worried about any deficiencies, it’d be best to get levels checked by a doctor.
Lastly and most importantly, multivitamins can interact with some common prescription medications by way of chelating (also called binding) the medicine (more specifically metal ions in the multivitamin like calcium, mag, iron, and aluminum) thus rendering the meds less effective to the body.
The challenge with a multivitamin is that it needs to jam all these “essential” nutrients into a pill or powder and sell it to you with a profit and still be affordable. Most multivitamins I’ve found cut costs here and there. Usually by using cheap forms of nutrients that aren’t very bioavailable (don’t absorb well, thus sort of useless) or downright toxic ingredients. There is no point in taking a multivitamin if your body can barely absorb the nutrients from it. So if you are going to supplement, pick a multivitamin with the most types of high bioavailable ingredients that don’t contain toxic additives and has a good balance of complexes that are safe for long-term consumption.
Yes, drinking tasty water is dangerous, and all the vitamins will harm you because… /sarcasm
Everything can be dangerous, depending on the circumstances and factors such as quantity and quality.
You’ve not provided any information on what it is you’re putting in the water. Companies sell multivitamins with very, very, very different ingredients.
However, assuming you’re taking a supplement that’s widely available and thus more likely to follow safety regulations, it’s is extremely unlikely to cause you any harm. If it’s halfway decent, it may provide some benefits.
The tasty flavor is most likely caused by artificial fragrance and either sugar or sweetener. These substances aren’t benefitial for your health. However, I believe it’s healthier to consume this multivitamin in water than a regular soda, because the soda has the same disadvantages while providing no benefits at all.
It is also possible that your body is craving the vitamins, and the reason you enjoy the taste is because you really need the multivitamin.