Eating too much salt is a huge problem. Globally, high salt can be linked to 1.65 million annual deaths from cardiovascular disease. High salt is often linked to high blood pressure, also called hypertension. However, some people who eat a lot of salt and have cardiovascular issues, have no hypertension. So, salt must be doing something other than just raising blood pressure.

A new study that looked at the kidneys’ endothelium—the cells that line the blood vessels—may explain what is going on. The endothelium is a smooth, protective lining that helps your blood flow easily and keeps your blood vessels healthy. It can make different substances and communicate with other cells to make sure your vessels work as well as possible. One of the most important factors the endothelium makes is called nitric oxide (NO).

Some of the ways NO promotes blood vessel health is by:

• Stopping the muscles around the blood vessels from growing too much, which makes it harder for vessels to relax
• Stopping fatty buildup from accumulating inside the blood vessels
• Stopping endothelial cells from dying

Endothelial cells that make NO are all over the vasculature in the entire body, but one of the best places to study these cells—and how salt affects them—is by studying the kidneys. The kidneys are full of tiny vessels. These vessels play an important role in how your body absorbs or gets rid of salt and water. The study’s researchers used rat kidneys to see how large amounts of salt changes endothelial NO production.

The researchers found that high salt reduced the amount of NO that the body produces. This means that without NO, the tiny vessels in the kidneys did not work as they should. If you think about this in terms of your diet, eating too much salt can make it hard for your kidneys to work right. It stops NO from doing its job well.

This study found that salt turns off certain genes by altering epigenetics. Essentially what happens is the “NO switch” gets turned off in the endothelial cells. That can be a problem because NO is very important for a healthy cardiovascular system.

One thing the researchers of this study found is that salt doesn’t cause kidney and heart issues just through increasing blood pressure—it also affects other parts of your body.

Scientists continue to work to understand exactly how too much salt stops NO from working in our tiny blood vessels. There is an unknown factor in the blood causing this change, but they are still trying to uncover that mystery.