Are supplements healthy? It depends.
I am a huge proponent of supplementation when done properly. While it's always best to get nutrients from whole foods, some are very difficult to get in optimal amounts through diet alone - even those that are extremely healthy. Moreover, certain circumstances and conditions increase our bodies' needs for particular nutrients. In these cases, supplements offer beneficial nutritional support that allows our bodies to function better and heal. To be clear, supplements should never be regarded as a replacement for a healthy diet; rather, they can be used in conjunction with a healthy diet to provide the necessary nutrients for optimal health.
That being said, supplement usage can be very dangerous. This is most often the case when a person comes across some sensationalized media report and then decides, without consulting a healthcare professional, to start taking whatever "has been shown" to have a desired effect. The truth is that the vast majority of the time, these media reports are based upon an individual study (often with major limitations!) from which no real cause-and-effect conclusions can be drawn. The subject requires significant further research before the public starts basing their health decisions upon its results.
Another problem with supplementation without supervision is that people do not understand that the "more is better" approach should never be applied. Many nutrients are toxic at high doses, making this a perfect example of the case of too much of a good thing! Dosages should be calculated according to a person's current health status and then carefully administered and adjusted as their health status changes. At the end of the day, supplements are very powerful substances whose usages should be monitored by health professionals with a strong understanding of nutrition.
A final note: The supplement industry is very, very poorly regulated. There is an enormous range in quality and there are a lot of items on the market that are mislabeled and outright dangerous. It's extremely important to select only high-quality, trustworthy products to ensure that you are using a product that will actually support your health. Please consult with a healthcare practitioner to determine not only which nutrients you should take, but also which brands you can trust.
Now I'd love to hear from you. Do you take supplements? If so, do you buy what's available at the store or do you vet your brands? What are your go-to brands?