Can Drinking Water Help with Blood Pressure Control?

November 14, 2021

by Cathe Friedrich

How many times have you heard it’s important to stay hydrated? Even mild dehydration can negatively affect your mood and motivation. Studies show it also causes fatigue and a mild headache. Plus, research shows many people walk around a state of mild dehydration and aren’t aware of it. Being as little as 2% dehydrated can cause headaches, fatigue, and lack of motivation. At this level of dehydration, most people aren’t even thirsty. Could that be you?

Dehydration affects all aspects of physical function since your body is so dependent on water. When you don’t drink enough water, your heart rate increases, but what effect does hydration have on your blood pressure? Can drinking water help with blood pressure control?

Blood Pressure and Hydration

Whether you have high blood pressure or not, it’s important to stay hydrated. When you’re dehydrated, your kidneys sense the low water state and release a hormone called renin. This causes your body to retain more sodium and water to correct the low fluid balance. Renin also acts on arteries, causing them to tighten. When they do, your blood pressure rises.

Dehydration tells your brain to release another hormone called vasopressin. Vasopressin acts on the kidneys to increase water retention, and, like renin, also causes blood vessel narrowing. So, renin and vasopressin, released in response to poor hydration, cause a rise in blood pressure. Plus, when you’re dehydrated, there’s less fluid in your blood vessels, and the blood that’s there thickens. Your body has to work harder to pump thickened blood, so your blood pressure rises.

Dehydration can also cause fluctuations in blood pressure. If you’re sitting or lying down and get up suddenly when you’re dehydrated, your blood pressure can drop suddenly and cause you to feel lightheaded or dizzy. If it’s severe enough, you could even pass out.

Other Risks of Mild Dehydration

There’s another reason to bring out the water bottle. Thickened blood from dehydration increases the risk of blood clots forming that could block a vessel. So, adequate hydration is healthier for your heart because it lowers the risk of blood clots. Drinking water is beneficial for heart and blood vessel health.

One study of young males found that mild dehydration affects endothelial function, how the inner walls of arteries react to stress. In fact, the effects of modest dehydration on blood vessel function was equivalent to what you’d expect after smoking a cigarette. Disturbingly, they saw the effects with only mild dehydration, around 2%. Since poor endothelial function is a risk factor for cardiovascular disease, not drinking enough water may be an underappreciated risk factor for heart attack and stroke.

If You Take Blood Pressure Medications

If you take medications for hypertension, it’s even more important to drink enough water and avoid even mild dehydration. Some of these medications are diuretics and remove fluid and electrolytes from your body. Some can also cause a potassium imbalance, leading to serious health consequences. Talk to your physician about how much fluid to drink if you take one or more medications for hypertension or cardiovascular disease.

How Much Water is Enough?

You may have heard you need 8 glasses of water per day, but that’s an estimate. The amount of water you need depends on how active you are, whether you’re sweating from exercise or fever, and the diet you eat. If you eat a diet rich in raw fruits and vegetables, you’re getting a significant amount of water from your diet and don’t need to drink as much as someone who eats foods low in water.

Exercise is also a factor. You lose water and electrolytes (sodium, potassium, chloride) when you sweat. If you exercise for a long time, especially in the heat, and drink only water, you don’t replace the electrolytes you lost through sweating. Fitness experts and nutritionists advise people who exercise longer than 90 minutes to drink a sports beverage or other electrolyte-rich drink in place of water. For example, there are instances of people dying during marathons from drinking pure water. They lost sodium and potassium through sweat, and only replaced water, leading to a critically low sodium level.

How do you know if you’re sufficiently hydrated? Check the color of your urine. If you’re hydrated, your urine should be no darker than pale yellow. If it’s darker, you have some catching up to do. As you drink more water, you should notice your urine color lighten.

If you need the motivation to drink more water, add a slice or two of lemon or lime to your glass. Doing this will make it taste better, and you’ll enjoy staying hydrated more. Citrus adds additional vitamin C too.

Another way to ensure you’re hydrating enough after a workout is to weigh yourself before exercising and again immediately after. For every pound that you’re down after exercise drink 16 to 20 ounces of fluid. If you’re exercising in a hot environment, the risk of dehydration is higher, so drink 6 ounces of fluid every 15 minutes during your workout.

The Bottom Line

Drinking enough water can help avoid imbalances in blood pressure, and even help with blood pressure control. Staying hydrated may even lower your risk of cardiovascular events, like a heart attack or stroke. Use your urine color as a marker of how well hydrated you are and your change in body weight. Also, ask your doctor whether you’re taking diuretic medications that could disrupt your body’s fluid balance.

References:

“Water’s unexpected role in blood pressure control ….” 14 Jul. 2010, sciencedaily.com/releases/2010/07/100706150639.htm.
“Water: The Unexpected Blood Pressure Drug — ScienceDaily.” 08 Feb. 2000, sciencedaily.com/releases/2000/02/000208075311.htm.
“High Blood Pressure Symptoms and Causes | cdc.gov.” 18 May. 2021, cdc.gov/bloodpressure/about.htm.
Watso JC, Farquhar WB. Hydration Status and Cardiovascular Function. Nutrients. 2019 Aug 11;11(8):1866. doi: 10.3390/nu11081866. PMID: 31405195; PMCID: PMC6723555.
“How Much Water Should You Drink When You Exercise?” webmd.com/fitness-exercise/features/water-for-exercise-fitness.
Chan J, Knutsen SF, Blix GG, Lee JW, Fraser GE. Water, other fluids, and fatal coronary heart disease: the Adventist Health Study. Am J Epidemiol. 2002 May 1;155(9):827-33. doi: 10.1093/aje/155.9.827. PMID: 11978586.