Here's the difference between your healthspan and lifespan—plus, how your diet factors in

For decades, scientists have studied lifespan to determine the impact of the factors that dictate how humans age. 

But in recent years, researchers have begun looking into a newer phenomenon: healthspan.

Lifespan and healthspan will always overlap in some way, but there is a major difference between the two, says Alan Cohen, associate professor at the Butler Columbia Aging Center at Columbia University.

Here's how each term is defined and how diet may play a role in lengthening them both, according to Cohen.

Lifespan is "the amount of time that passes between when you're born and when you die," Cohen tells CNBC Make It. 

While healthspan is "basically how long you're living in good health. But, in order to define that, you need to define what good health is," he adds.

Living a long life with conditions like severe dementia or chronic pain indicates that your lifespan is lengthy, but your healthspan has ended, Cohen notes.

Therefore, "healthspan will always be shorter than or equal to lifespan," but never longer, he says.

Most people want to increase their lifespan as much as they can, but if quality of life is important to you in your final days, healthspan is what you'd want to lengthen.

Cohen co-authored a study, published in September of this year, that investigated the connection between nutrient intake and healthy aging by tracking the dietary intake data of 1,560 older adults in Canada.

These were the four biggest takeaways from their findings:

1. You need various types of nutrients in your diet, including sugar and fat – just have everything in moderation.
2. How much of a specific vitamin you need depends on your intake of other vitamins. For example, the amount of vitamin E your body needs will shift depending on your vitamin C intake. 
3. Diet is like a plateau, not a mountain – there isn't a peak diet that will offer the highest health benefit for all people because everyone's bodies aren't the same. Just don't "fall off the cliff" by engaging in eating behaviors that will increase your risk of diseases.
4. There are different aging metrics, so one diet won't decrease aging across the board.

Here's what may help for healthy aging, and a longer healthspan, when you're an older adult, according to Cohen:

• Ensuring that your body is getting enough vitamin C
• Getting more vitamin E from your diet – not from supplements
• Eating more protein

"There's intermittent fasting or the Ketogenic diet, [and] I don't want to completely write off the idea that some of these diets have some benefits," says Cohen.

"We are really overthinking our diets, and there won't be a silver bullet solution that we can say to everybody, 'Eat this much of this and that much of that, and if you do that, your health will be as good as it can be.'"

Sign up now: Get smarter about your money and career with our weekly newsletter

Don't miss:

• 5 daily practices could up your chances of living to 90—check out this life expectancy calculator to see more
• People who live to 100 don’t eat like typical Americans: Here are ‘the 5 pillars of a longevity diet’