Happy Friday! Today we’re going to cover a topic that I don’t see covered nearly often enough: salt sensitivity and how it impacts health. Before we begin, a quick reminder that this article is for informational purposes only. Many people are put on low-sodium diets by their dietitian or physician for serious medical conditions such as heart failure. Please do not make changes to your nutrition therapy without getting the approval of your medical team first! They can best evaluate (based on factors such as your medical history and lab values) what sort of nutritional plan may be optimal for you.
In this article:
- What is salt-sensitivity?
- Do you know how much sodium you should be aiming for?
- Do athletes have higher sodium needs?
- Need more information?
What is salt-sensitivity?
People have varying blood pressure responses to chronic changes in the amount of salt in their diet. Around 25% of the population is “salt-sensitive,” which has been defined as “a change in blood pressure of 5–10% (or at least 5 mmHg), in response to a change in salt (NaCl) intake.” When a person’s blood pressure is not impacted by changes in dietary salt intake, they are considered “salt-resistant.” A final group (10-15%) is “inverse salt-sensitive,” meaning their blood pressure drops as their salt intake goes up. Salt sensitivity is thought to be a risk factor for cardiovascular disease and other diseases, independent of whether the person has high blood pressure. Unfortunately, no convenient diagnostic test is widely available at this time to determine who is salt-sensitive and who is not. More research is definitely needed in this area.
Do you know how much sodium you should be aiming for?
The sodium guidelines were recently updated by the National Academies of Sciences, Engineering, and Medicine. One major change is the removal of the tolerable upper intake level (UL) for sodium, and replacement with a “chronic disease risk reduction intake” (CDRR). The rationale for this renaming was that it was difficult to separate chronic disease risk related to high sodium intake from a toxic level of intake. According to the CDC, most Americans do eat far more sodium than the CDRR, and it is mostly coming from restaurant meals and processed foods. However, since the impact of salt intake on cardiovascular disease and blood pressure is not linear (it is a J-shaped curve), the current one-size-fits-all recommendations that we have for sodium are not adequate. For a subset of the population, the general recommendation may even have detrimental effects, such as excessive hypotension (blood pressure that is too low) in the elderly.
The American Heart Association has recognized (article here) that “the reproducibility of SSBP [salt-sensitive blood pressure] tests separated by weeks or years supports the conclusion that underlying differences in sodium sensitivity exist among individuals.” Unfortunately, “translating this knowledge on SSBP to clinical practice is practically impossible because the traditional protocol requires a 3-day hospital stay and attempted briefer protocols in the clinic failed validation.”
Do athletes have higher sodium needs?
Like those with inverse salt-sensitivity, athletes are another group whose sodium needs may not align with the sodium dietary reference intakes. As noted in the graphic above, the CDRR were calculated based on sedentary estimated energy requirements. Exercise very often results in an increased need for sodium, particularly if the person loses a lot of salt in their sweat, or if they are exercising in hot weather. The concentration of sodium that is lost in sweat is highly variable among individuals (anywhere from 230 to 3,358 mg/L in adults), with some being very “salty sweaters” while others are not so much.
There are some easy ways to figure out if you are one of the folks who are prone to large sodium losses when you work out. After the sweat dries, your skin may have some grainy residue, or your clothing may have white streaks. If it stings if sweat drips into your eyes while you are working out, this is another indication that you may be a salty sweater. If you are losing large amounts of salt in your sweat, the stringent dietary recommendations for sodium listed above may not be appropriate for you. The National Academies states in their DRI report that “Because of the variability in heat acclimatization and sweat sodium losses, an individualized approach considering intensity of physical activity, temperature exposure, and sweat loss is needed.” Tailored nutrition information is key for athletes and others with elevated needs for sodium (as well as other electrolytes).
Need more information?
If you are trying to follow a low-sodium diet, eating out can be one of the toughest challenges.On the other hand, if you fare better with a higher sodium intake, restaurant meals will most likely help you out.
Unrelated, I wanted to take a moment to recommend the Obesity and Energetics Offerings email list before we end today. They have a section “Headline vs. Study” which looks at how the information in recent scientific studies get distorted in the press release and the headline. Check out the (sadly typical) example below…