Cardiovascular diseases are the number one killer in the world today. Proper hydration supports heart health. Your heart does not need to work so hard if you are hydrated. Dehydration causes a decline in blood volume and initiates blood thickening. As the volume of your blood decline your blood pressure goes down as well. In order to balance the blood pressure, your blood vessels begin to contract and your heart starts to work harder to pump more blood. This means in short that your heart has to pump thicker blood through narrower blood vessels which is obviously strenuous to your heart.