My dear Dr. Rabin, you drag more vampiric charlatans into the light of day than that do-gooder Van Helsing. Which brings us to today's horrific inquiry: Is blood really good for you? The "Blood Countess" Elizabeth Bathory bathed in it; the Rolling Stones supposedly got (get?) transfusions regularly; and then, of course, there's Dracula. Please reply soon because I have some important decisions to make by the end of the month.
—R. Enfield (known, during daylight, as John R.)
Let's be clear: Blood is essential, but homemade is still vastly superior to any, shall we say, imported variety. Authors like Anne Rice, and tough blondes like Buffy, have romanticized the blood-drinking characters that were—for hundreds of years—feared and reviled. Those suckers aren't quite so scary anymore. Rather, sanguinarians ("vampire" is so 19th century) are now sensual, fearless, eternally youthful immortals with a social conscience. Hell, if Lestat would run in the primaries, he might even win New Hampshire.
To fully answer your question, I must address each of your supporting statements. Indeed, the Countess Elizabeth Bathory was a wealthy, Hungarian turn-of-the-17th-century serial killer who is most noted for accusations that her extreme vanity led to bathing in the blood of her victims. Her prey were mostly local peasant girls lured by offers of work, and Bathory ultimately dispatched each following severe beatings, mutilations and torture. There is little doubt she enjoyed this pastime, as plenty of evidence exists that she killed at least 30 women (and probably many more). But according to historians, actually soaking herself in their blood is a beauty regime that appears completely invented. My own morbid calculations show that it would take at least 15 victims, thoroughly exsanguinated, to provide enough blood for even a thin bath. Assuming for the moment she could work out the logistics, the lack of anti-coagulants might pose an additional problem; I suspect that even a hardened, narcissistic serial killer would be grossed-out sitting in a tub of clots.
Turning to The Stones, we can assume you're alluding to an altogether different tale that guitarist Keith Richards had "all his blood changed" in order to kick a heroin addiction. Not so, says Snopes.com. As the urban legend investigators tell it, Richards once went to Switzerland for hemodialysis, a treatment that simply filters your blood in the same manner your own kidneys do—it doesn't swap it out. Granted, he may appear vampiresque, but his pharmaceutically fortified blood remains entirely his own.
In recent years, a vampire subculture has arisen that has essentially fetishized the drinking of both human and animal blood. In the latest case of eat and run, a man in Hong Kong was just arrested after fleeing a hospital where he had grabbed three blood tubes from a testing lab and downed the contents. More consensually, there are groups of night-loving enthusiasts whose vampire role-play often culminates in oral blood exchange. Somewhat smaller (with, perhaps, some crossover) are the numbers of these people with true psychiatric disorders that involve a penchant for plasma. An attempt has been made to classify such compulsive blood-drinkers as suffering from an invented disease called "Renfield's Syndrome" (after Dracula's loyal henchman), but such individuals already fall into more than enough existing categories.
Though it is true that Kenya's Maasai population will drink cattle blood, this is usually a matter of survival during periodic times of severe drought. In their case, blood is simply a protein source and, often mixed with cow's milk, allows both the traditionally nomadic people and their livestock to live another season. In Western society, there is no such upside, and the significant dangers certainly outweigh whatever savory delights a night-stalker might enjoy.
Obtaining blood, even from a willing participant, must involve biting, puncturing or cutting—all of which leave the donor open to bacterial infection. In a similar vein, ingesting a literal Bloody Mary may expose the drinker to blood-borne pathogens ranging from hepatitis to HIV. Animal blood is no safer: Whether slaughterhouse-obtained or home-collected, contamination with infectious coliform bacteria is far too easy, and exposure to parasites and other circulating microbes are real threats. We know you're immortal; no need to prove it.
So, my friend, I cannot give even an anemic recommendation for blood as a dietary supplement. However, if you still feel the need to suck the life out of others to make you stronger, might I suggest a career in corporate law? The dress code is still basic black, you would finally be properly despised again, and I'm certain you'd prefer the requisite Kobe steak to a sharpened one made of wood.