All the things we do for natural and healthy lifestyles have the same goal: to live our best lives for the longest time we can. A recent study suggested that optimal hydration may be a factor in healthy aging in humans, and knowing how much water a day to drink is important.

Days of old generally suggested 8 cups of water a day and you'd be good. That's 64 oz that was recommended, and while that's a good starting point, new research suggests that the amount of water a day you should drink varies based on a lot of different factors.

Still, optimal hydration is a factor in many health benefits. A recent study suggests that higher hydration levels during middle age may help reduce risks of chronic disease and even premature death.

Researchers from the United States National Institute of Health (NIH) looked at middle-aged people who had higher serum sodium levels in their blood. Serum-sodium levels may be elevated if a person hasn't consumed enough hydrating fluids, and these elevated serum sodium levels may be indicators that one is going to have a higher risk of mortality and have poorer health outcomes.

Generally speaking, a healthy serum sodium level range is 135-145 milliequivalents per liter (mEq/L). Typically, the most common cause for higher sodium levels is a water intake deficiency.

The researchers also found that those with low serum sodium levels (less than 142 mEq/L) had a 50% increased risk of 'being' older than their chronological age, based on physical symptoms.

In addition, researchers found that participants with low serum sodium levels had up to a 50% increased risk of being older than their chronological age.

The researchers were with the NIH's Laboratory of Cardiovascular Medicine and performed a cohort analysis of data from the 1985–2021 Atherosclerosis Risk in Communities (ARIC) study. The study's initial 15,752 participants ranged in age from 45 to 66 and were followed for 25 years.

The new research used serum sodium levels as an indicator for water consumption as high levels of serum sodium are closely parallel with water insufficiency or hypohydration.

Dr. Natalia I. Dmitrieva is the lead study author and an NIH researcher in Bethesda, MD. In an article with Medical News Today, she said the study was motivated by earlier research the authors had done that suggested lifelong hypohydration “accelerated degenerative changes and shortened lifespan” in mice.

She said that water-restricted mice lived 6 months less than sufficiently hydrated mice and in human lifespan terms, this equated to about 15 years.

The original findings in mice mirrored what the research team concluded in the recent study. According to Dr. Dmitrieva, long-term habitual hypohydration increases the risk of developing chronic diseases later in life as well as dying at a younger age.


The good news is that sufficiently hydrating can be done pretty easily, but it needs to be considered carefully. Simply put, eight glasses of water a day is not sufficiently supported by evidence as an adequate amount for every human being.
In fact, the Centers for Disease Control and Prevention (CDC) states the optimal amount of water a person should consume daily depends on each individual. The guidelines suggest the following:

  • In those between the ages of 20-39, the CDC suggests an average of 51 ounces daily.
  • In those between the ages of 40-59, 43 ounces of water per day is the average.
But experts suggest even those guidelines need to be more specific.

How much water should you drink a day?

Some experts believe some people may require less than the suggested amount of water. For instance, if someone with heart failure drinks too much water, it can cause fluid backup and make it hard for that person to breathe. Additionally, people with kidney failure may need to drink less since their kidneys are compromised and less able to maintain a balance of fluid. This directly contradicts the thought that 'flushing' kidneys out with plenty of water is always beneficial.

Still, others may require MORE water, particularly those with higher body mass indexes (BMI).

More and more, the thought is that drinking between half an ounce to an ounce of water per pound is a good guideline, which can vary based on your activity level, sex and more. It can also depend on what your daily food and other liquid intake is. For instance, you can count tea, coffee and electrolyte beverages toward hydration, though that shouldn't be your main hydration source. Foods like watermelon, cucumbers, strawberries or pineapple can also offer hydration.

Dr. Dmitrieva said that surveys show that about 50% of people don't drink the recommended amounts of water, and this is especially in children and older people. In fact, in older people, thirst sensation deteriorates, so we tend to drink less.

The best way to stay hydrated is to keep track of what fluid you drink each day and to drink enough in hot environments or when engaged in intense sports activities.

Signs of dehydration

Whether we're engaged in intense activities or not, we lose fluids throughout the day. We go to the bathroom, sweat, breathe and more. It's imperative to replace those liquids or we'll become dehydrated, and increase our risk for chronic illness and shorter lifespans.

What does dehydration look like? Here are a few signs:

  • Dry Mouth. If your mouth is dry, unless you're on medicine that may make that happen, odds are your cells are already screaming out for hydration. It's not just about whetting your whistle; rehydrate!
  • Thirst. Same goes for thirst. If you're thirsty, you're probably dehydrated. A key is to hydrate throughout the day and prevent thirst from even happening. Consistency is key.
  • Decreased urine or discolored urine. If you're not going to the bathroom often, that may be good if you're in the middle of a large crowd with no bathroom in sight, but your body doesn't love it. Or if your pee is the color of neon, that's not a great sign either. Shoot for going to the bathroom frequently, as it flushes toxins and going for clear urine as your sign of good hydration.
  • Muscle cramps. This could be a result of dehydration. Eat a banana and drink a glass of water to see if that helps.
  • Headache, Dizziness and lethargy. You may feel like you've got a hangover and that's probably because that's what happens when you've had too much to drink--you're dehydrated! There's a reason you're supposed to drink a glass of water for every alcoholic drink you have--it's to replace the hydration alcohol takes or else you could feel like you were out clubbing the night before.