In extreme b deficiencies yes. I would say that as most of us have access to an internet connection we are probably also fortunate enough to live in countries where there are adequate dietary provisions, and that nobody here is vitamin b deficient. I would never take a vitamin b complex, for one thing vitamin b6 is toxic in higher doses and can cause neuropathy. Search for b6 toxicity and you will find thousands of anecdotal cases. It's simply not worth taking any vitamin b supplements unless you are absolutely certain you have a deficiency and even then dietary changes will be able to correct this.