Are there specific types of vitamin deficiencies that are more dangerous than others?

Not really: Vitamins are an essential requirement of normal body function. Any severe vitamin deficiency can have dire effects. The good news is that few americans have vitamin deficiencies other than vitamin d among those who get little sun exposure, and vitamin B12 among vegans and seniors. Avoid deficiencies by eating a variety of fruits, vegetables, beans, nuts, and whole grains and some wild salmon.