Common and often critical nutritional deficiency(s), are based genetics. A significant percent of the population may have difficulty in converting nutrients in food to usable activated vitamins. I believe the population that needs to be aware of this anyone with a chronic illness or a health issue that is poorly responding to care.
The nutrients that are of primary concern are: Folic Acid, Vitamin B6, B12, and B2.
(an optimal product should have similar ingredients as found here).
These deficiencies are caused by a single nucleotide genetic polymorphism (SNP) that results in a reduced efficiency in a live metabolic process called Methylation.
To read a 2 page summary about Methylation (PDF File) click on this link here or to learn more follow the link of Dr. Laurie Mueller on left. Also the Khan Academy always does a good job in explaining this and many health related issues.