Getting Personal: How Much Sodium Do We Need?

Here at the IFIC Foundation and across the internet, we’re seeing, reading and writing more and more about personalized nutrition. Our genetics and environment play significant roles in how our bodies respond to and use certain foods and nutrients. Today let’s focus on sodium.

Sodium is a vital mineral that makes up one-half of sodium chloride, more commonly known as table salt. We can add it to foods ourselves when we sprinkle salt on soups, pasta or roasted vegetables, and it’s also found in many packaged foods, where it not only adds flavor, but also contributes texture and preservative functions. Ninety percent of the sodium we consume is in the form of sodium chloride, but other compounds like sodium nitrate and sodium nitrite are used as antimicrobial agents in some foods. More than 70 percent of our salt intake comes from packaged or restaurant foods, 10 percent is added during cooking or at the table and 10 to 15 percent occurs naturally in foods, especially meats. Fruits and vegetables are naturally low in sodium.

How does sodium affect our health?

All of us need a small amount of sodium to keep our bodies working as they should. It’s critical for things like muscle function (including the heart) and keeping our nervous system working properly, and it helps to control fluid balance. The 2015-2020 Dietary Guidelines for Americans recommend that we consume less than 2,300 milligrams (mg) of sodium each day, which is the amount of sodium in about one teaspoon of table salt.

However, it’s well-known that most Americans — an estimated 90 to 95 percent of us — eat much more than this (3,400 mg on average, every day). Usually our kidneys do a great job of regulating our sodium intake by excreting what we don’t need within a few hours. But when this system gets out of whack, problems can arise. Consistently consuming too much sodium, usually over several years, puts extra stress on the heart and blood vessels. Over time this can contribute to high blood pressure. High blood pressure, also called hypertension, is associated with risk for heart disease and strokes. There are other risk factors for hypertension, including being overweight or obese, eating an unhealthy diet and lack of physical activity, to name a few. Along with making other lifestyle changes like eating well and exercising more, decreasing sodium intake is one way to help bring down blood pressure.

So what’s the “personal” aspect of this health connection?

Even though it’s important to have dietary guidelines for our U.S. population as a whole, research continues to demonstrate that “one size fits all” doesn’t apply. Blood pressure responses to dietary salt intake vary considerably from person to person, a phenomenon called salt sensitivity. Some people are very efficient at removing sodium from the bloodstream without an increase in blood pressure, and others — known as “salt-sensitive” individuals — cannot excrete sodium without a blood pressure increase. Age is a factor in this phenomenon: Sensitivity to salt increases with age, so a 60-year-old person may see a greater reduction in blood pressure from eating less sodium than a 20-year-old. Genetics also play a very important role, though it’s one that is still being defined.

About 25 percent of the U.S. adult population is salt-sensitive, and a little less than half of these people also have hypertension. Salt-sensitive people are likely to benefit the most from decreasing their sodium intake to around the recommended 2,300 mg per day (and in some cases, aim for lower than that). For people with particularly high sodium intakes, a reduction of 1,000 mg per day has been shown to lower blood pressure regardless of achieving the recommended goal.

The problem? So far, there’s no practical, affordable and easy way to test for salt sensitivity at the doctor’s office. Even though researchers have identified a few genes that may be involved, we still don’t know enough to be able to explain how any one variation — or more likely, a network of genetic differences — affects blood pressure in humans. In order for health professionals to focus on people who can benefit the most from lowering their salt intake, better diagnostic methods are still needed.

…okay. So what should I do?

Even though much more research needs to be done to determine the best indicators of salt sensitivity and to find better methods for diagnosis, everyone can take steps to keep sodium intake in check. The American Heart Association has an extensive list of ways to lower sodium intake or keep it near 2,300 mg per day, but you can start by reading nutrition labels to check how much sodium is in a serving of your favorite foods, selecting “low-sodium” versions of foods like soups and broths, choosing fresh fruits and vegetables for meals and snacks, and getting creative by flavoring your foods with sodium-free herbs, spices and citrus.

We still have a lot to learn about how salt affects each of us personally, but these choices will keep us on the right track to healthful choices.