The pillars of good health are mostly common sense. Eat plenty of fruits and vegetables; exercise often; sleep well; avoid too much booze, hard drugs, and probably rock 'n' roll. It's the devil's music!
Those aspects of a healthy life are the tedious reality, but there's another factor that's proven to be the biggest indicator of whether someone will make it happily into old age, and this one's a lot more fun: the quality of your social life.
Surrounding yourself with good people you like isn't just some hippie, feel-good mantra; its role in overall health is backed by scientific studies of hundreds of thousands of people.
So there may be something to be said for ditching your post-work gym session to grab drinks with your friends.
People with good relationships live longer
For 75 years, researchers at Harvard have studied the same 600+ people throughout their lifetimes to see what determines a long, happy life.
Known as the Grant & Glueck studies, or the Harvard Study of Adult Development, they're some of the longest-running examinations of overall health and happiness. With most of the participants now in their 80s and 90s, researchers have found some clear patterns that the happiest and healthiest people had in common.
It turns out that they all had high-quality relationships with other, according to Dr. George Vaillant, who headed the Grant study for 42 years. Solid relationships also proved to be a commonality among people who lived the longest. On the flip side, those with negative personal relationships or no personal relationships at all died sooner.
"Relationships are super-important; they're right up there alongside not smoking, exercise, diet, not abusing drugs," says Dr. Robert Waldinger, current lead researcher on the Harvard Study of Adult Development.
If all your best friends are smokers who love sitting on the couch all day, well, that's a dilemma you have to address on your own.
Good relationships make you physically stronger
That strong relationships with people you enjoy boost your emotional well-being isn't exactly earth-shattering news. But researchers and doctors have also found that they have a positive impact on your physical health.
And it's not just the effect of happier people viewing themselves as healthier. It's tangible. "We began to realize that this is a real thing, that somehow relationships, the number of relationships you have, and the quality of the relationships, actually sort of gets into your body and makes a difference," Dr. Waldinger says.
Friends help you blow off steam
You know those days when everything seems to go wrong and you just need to complain to someone? Venting is good for you! "If you have someone who is a really good listener and you just need to blow off steam about your day, then you can actually feel your body calm down a lot of times," Dr. Waldinger points out.
Part of the reason this works is that blowing off steam helps your body regulate its fight-or-flight response. If you're frazzled all the time, your body operates in a continuously stressed state, which wreaks havoc on your internal chemistry.
"People who have bad relationships, who have very stressful lives without the ability to calm down, are chronically in a kind of low-level fight-or-flight response," adds Dr. Waldinger. "And that changes your body chemistry." High levels of stress hormones can create a state of chronic inflammation, a precursor to disease.
"Normally your blood will fight off infections and that kind of stuff, but chronic inflammation is bad for you," he says.
There's no ideal number or type of relationship
What gets tricky about maintaining this pillar of health is that it also requires the effort of someone else. Dragging your ass to the gym or choosing a salad for lunch are decisions that you alone can make. Keeping in touch with your friends from college requires participation on both ends.
It's also tough to prescribe the best social situation for everyone. Some people are introverts who prefer just a few close relationships, while others are extroverts who get energy from being in big groups.
Dr. Waldinger emphasizes that it's not just romantic partners that matter either; even if you're single and live alone, but have some quality friendships or close relatives, that's definitely beneficial for your overall health.
Relationships are important at every age, but become more difficult as you get older
Many people think of "getting healthy" as a series of changes undertaken in middle age that will increase the odds of living to 100 -- fading youth is a powerful motivator. But maintaining good relationships is vital from the moment you enter the world.
"What the research shows is that it's across all ages. It's literally from the time you're a newborn until the time you die," he says. The quality of parenting newborns receive, for example, impacts them throughout their entire lives. Similarly, elderly patients who receive good hospice care tend to be happier and live longer, he says.
That's right. Even people in hospices live longer when they have better relationships.
Keeping up with your friends is just as important in high school as it is in your 40s, as it is in your 80s, and beyond... if you make it that far. Of course, the longer you live, the more difficult it is to foster solid bonds with others. Life (and death) have a knack for interfering.
Women tend to be more social than men
This is a stereotype that's been reinforced time and time again, with very real effects on health. For example, in traditional long-term heterosexual relationships -- like many observed in the Grant & Glueck studies -- women are responsible for maintaining social calendars for the couple. The fact that this responsibility is related to antiquated gender roles doesn't affect the result: Women usually have better relationships, and also live longer.
This holds true to Dr. Waldinger's findings. He says women were better about keeping up their friendships and social lives than men were, noting that many men wake up and realize they don't have any friends, or not nearly as many as they used to.
"Once you get out of the drinking buddy stage, a lot of guys will just settle into their work, and they’ll have a partner, and they kind of just don't pay much attention to anything beyond that," he explains. "Women are usually better at paying attention to their social relationships. Now, that's a gross generalization, and some men are really socially aware, and some women are clueless, but by in large, women are socialized more as they grow up to pay more attention to relationships."
Dr. Waldinger adds that his work on this study has made him more cognizant of the role his wife plays in commanding their social life -- and to what extent he's doing his part.
"I have to actually think to myself, 'Am I keeping up with my friendships, with my individual friendships?'" he says. "I have to pay a lot more attention to my individual friendships, or they would just go away."
Bottom line: Focus on where you're spending your time
In his TED Talk on happiness, Dr. Waldinger mentioned that over 80% of millennials listed "getting rich" as a major life goal, followed by 50% wanting to be famous. These ambitions are all well and good... except they aren't proven to lead to health or happiness. So they're not all well and good, actually.
"A lot of people, especially young adults, are trying to figure out 'where do I invest my time?'" Dr. Waldinger says. "So you can spend your whole time -- nights and weekends -- working to advance your career, and that would probably advance your career. But it might really screw up your life."
Although there's no official standard for where personal relationships rank compared to diet, exercise, sleep, and all those other common-sense health habits, they require just as much of an investment, if not more, to reap the rewards.
"It doesn't mean that one [healthy habit] replaces the other, but they all kind of work together," he emphasizes. "So rather than figuring out which one is more important, it's figuring out what's a really good combination. And maybe a combination where the sum of the parts is bigger than the individual parts."