Why Drink Water? Part III

May 21, 2015

Why Drink Water? Part III

Stay Hydrated for Lower Blood Pressure and Better Heart Health

Welcome back! In the first two posts in this series I talked about how starting to drink enough water will noticeably improve the way you look and feel. Good motivators, right? As I said before, how much water you drink affects every system in your body, so now I’d like to go a little deeper and talk about how staying at your optimal hydration level can improve your cardiovascular health, and even extend your life.

When it comes to heart health in the United States, the numbers aren’t good. According to the National Health and Nutrition Examination Survey, 33.5% of US adults ages 20 and over have hypertension. This means an estimated 76.4 million adults in this country have high blood pressure! Unfortunately, high blood pressure and cardiovascular disease are often not considered until you or someone you know has had problems diagnosed by a physician.* I would like you to think about it today with respect to how even slight dehydration can affect your heart health.

The American Heart Association recommends a healthy diet and weight, exercise, and not smoking as the main controllable lifestyle factors in the prevention of cardiovascular disease. However, researchers at Loma Linda University have shown that increasing your water intake can be an effective addition to this list as well. In a long term study titled “Water, Other Fluids, and Fatal Coronary Heart Disease” published in the American Journal of Epidemiology, research showed that participants who drank 5 or more glasses of plain water a day lowered their risk of dying from a heart attack by half or more when compared to those who drank 2 or less glasses of water a day. These were all healthy men and women without a history of heart disease, stroke or diabetes who were different mainly in how much water they drank.

The study says that, “Whole blood viscosity, plasma viscosity, hematocrit, and fibrinogen are considered independent risk factors for coronary heart disease and can be elevated by dehydration.” What does this mean though? Even though there are other chemical factors affected by dehydration that will affect your cardiovascular system, for our purposes we will focus on viscosity. We touched on viscosity before in the second post in this series, but let’s look at it again to show why it matters. You will see how not drinking enough water will affect how your blood flows, and what that does to your heart in the long run.

Viscosity is the description of how thick a fluid is. A thin fluid has a low viscosity, and a thick liquid has a high viscosity. Pure water is thin and flows freely but as you add solids it flows less easily, so it has a higher viscosity. Your blood is composed of water and solid components that are carried around your body via your circulatory system. When your blood has more solids and less water it is harder for your heart to pump it around your body because it is thicker. That means your heart has to work harder with every beat just to keep you alive. The people in this study who drank 5 or more glasses of clear water a day had a consistently lower blood viscosity, making it easier for their heart to pump. These people were also found to have almost a 50% lower incidence of cardiovascular problems later in life. The outcome was clear in this long term study- participants who drank five or more glasses a day lowered their risk significantly more than those who didn’t!

That study focused on the long term effects of hydration on cardiovascular health, but wait, there’s more! We also have some good research on how hydration affects us on the cellular level. A different study was performed in a lab on blood cells affected by sickle cell anemia, which looked at how the cells acted with different levels of dehydration. Sickle cell anemia is a blood disorder which causes the cell to be crescent shaped, like a sickle. This irregular shape causes the cells to clump together and not flow and carry oxygen normally. The study was performed to see how hydration affected the way sickle cells and normal blood cells function when they were dehydrated.

Interestingly, this study found that dehydration made normal red blood cells adhere to each other too![3] They stuck to each other more when they were less hydrated which made them act more like the irregular “sticky” blood cells in sickle cell anemia. In addition to this they also found that actual sickle cells became less sticky when they were well-hydrated, acting more like normal blood cells. The take-away message from this study is that even slight dehydration will make your blood cells stick together more than usual and function poorly as if they actually were abnormal cells! It also suggests that people who have sickle cell anemia should pay special attention to their hydration levels so at the very least they don’t aggravate the disease symptoms, and possibly even help their blood to flow better by staying well-hydrated.

Basically, we have just looked at evidence at both whole-body and microscopic research levels that the amount of water you drink affects your cardiovascular system. Prevention is the best medicine with cardiovascular health of course, but it’s never too late to start good habits that can help reverse issues you’ve already discovered. As I said in earlier posts, our office recommends half of your body weight in ounces per day*, and I hope this series has helped you to understand why we say this. Your health can be improved with just a few extra glasses a day though, so do what you can. I welcome your questions or comments as always. Thanks for reading!

*IMPORTANT NOTE: If you have been diagnosed with any cardiovascular, liver or other systemic disorders or are taking medications to treat them ask your doctor before you adjust your fluid intake. If your doctor has already adjusted your fluid intake, follow their instructions exactly. Your personal physician’s advice overrides generalized hydration guidelines.

Sources:

[1]Chan, J., Knutsen, K. et.al.: Water, Other Fluids and Fatal Coronary Heart Disease. Am. J. Epidemiol. (2002) 155 (9): 827-833.

[2]Manz, F.: Hydration and Disease. J Am Coll Nutr October 2007 vol. 26 no. suppl 5 535S-541S

[3]Wandersee NJ, Punzalan RC,et. al: Erythrocyte adhesion is modified by alterations in cellular tonicity and volume. Br J Haematol 131 :366– 377,2005

[4]American Heart Association 2011 Statistical Update – http://circ.ahajournals.org/content/123/4/e18.full