Low-Sodium Diets: Rethinking the Science
"Watch your salt intake!" is a maxim we often hear from the nutrition world, but new research released last month indicates that there is more to the story.
Before going further, it is important to define "salt." In its most general form, the word "salt" is an umbrella term for the electrolytes sodium, potassium, magnesium, calcium and chloride, all of which are lost through sweat and all of which are vital for a variety of bodily functions. In the field of nutrition, salt usually refers to sodium. Among other things, sodium helps regulate blood pressure by working with potassium to move fluid through the body. This process is assisted by a balance of the two minerals, and if a person consumes too much of one type of mineral the process will be hampered. (You can learn more about the ratio process here.) Because the average adult does not consume enough potassium, many people have an excess of sodium, and a chronic imbalance of these two minerals can lead to higher blood pressure. Thus, it is often recommended to keep sodium intake low in order to keep the ratio in balance.
However, as a recent study indicates, lowering sodium may not be as effective at lowering blood pressure as previously thought.
The background
The standard recommendation for Americans is to consume a maximum of 2,300mg of sodium per day. This equals about 5.7g of salt, aka sodium chloride, or roughly the amount contained in 1 teaspoon. Each person's physiology is slightly different, so 2,300mg of sodium will have a different impact on different people. Also, because blood pressure is largely regulated by the ratio of sodium to potassium—and not the exact amount consumed—this is just a recommendation.
For the past 20 years, scientists have known that people with high blood pressure who do not want to lower their salt intake can simply consume more potassium-containing foods. Why? Because it is really the balance of the two minerals that matters. In fact, Dutch researchers determined that low potassium intake has the same impact on your blood pressure as high salt consumption. Nevertheless, common wisdom remains that increasing sodium intake increases blood pressure. To test this assumption, researchers at the Boston University School of Medicine examined more than 2,600 people for 16 years.
The study
To gather data for the study, researchers looked at 2,632 men and women between 30 and 64 years of age who participated in the 16-year Framingham Offspring Study, a long-range heart health study of people from Framingham, Mass. (The original cohort was called "The Framingham Study.") By using dietary journals, the researchers measured sodium intake, as well as intake of other minerals that help regulate blood pressure, such as potassium, magnesium and calcium. The participants had normal, healthy blood pressure readings at the start of the study.
The results
"We saw no evidence that a diet lower in sodium had any long-term beneficial effects on blood pressure. Our findings add to growing evidence that current recommendations for sodium intake may be misguided," said Lynn L. Moore, DSc, associate professor of medicine at Boston University School of Medicine.
The paper is clear in its takeaway that lowering sodium does not lead to better blood pressure levels. In fact, while all participants started with normal blood pressure readings, participants who consumed less than 2,500 milligrams of sodium a day had higher blood pressure at the end of the study than participants who consumed higher amounts of sodium. This research finding was echoed a year ago in a study published in The Lancet, which found that people who consumed less than 3,000mg of sodium a day had the same level of risk for heart disease as people who consumed more than 7,000mg a day.
The Boston University study also found that participants who consumed high levels of potassium, calcium and magnesium tended to have lower blood pressure levels. That is most likely because blood pressure is regulated by ratios of electrolytes, rather than their absolute values. By consuming higher amounts of potassium, participants could have mitigated high levels of sodium intake, resulting in normal blood pressure levels.
"This study and others point to the importance of higher potassium intakes, in particular, on blood pressure and probably cardiovascular outcomes as well," said Moore. "I hope that this research will help refocus the current Dietary Guidelines for Americans on the importance of increasing intakes of foods rich in potassium, calcium and magnesium for the purpose of maintaining a healthy blood pressure."
Where supplements fit in
Five electrolytes in particular play an important role in maintaining normal human muscle function: sodium, potassium, magnesium, calcium, and chloride. A shortage of any one of these electrolytes can affect athletic performance. This means that as an endurance athlete who routinely loses electrolytes through sweat, you need to be replacing these electrolytes in order to maintain performance. If you do not, your output will be reduced.
In fact, researchers at Camilo José Cela University examined in a double-blind study the performance of 26 triathletes who competed in a half-distance race, and found that athletes who replaced lost electrolytes with a full-spectrum electrolyte capsule finished the race 26 minutes faster on average than athletes who hydrated with sports drinks alone.
What if my doctor has me on a low-sodium diet? If you are on a sodium-restricted diet, you should consult your physician when considering the use of supplemental electrolyte products. As part of an exercise regimen, these products are designed to replace lost electrolytes. They are not designed to be part of a normal diet, as daily food intake provides sufficient electrolytes for regular activities.
It is worthwhile to note that only a small percentage of the population reacts to dietary sodium with higher blood pressure. Large-scale scientific reviews have determined that there is no reason for people with normal blood pressure to restrict their sodium intake. But if you already have high blood pressure, you may be "salt sensitive." As a result, reducing the amount of salt you eat could be helpful.
Conclusion
While the researchers in this study advocated for raising the recommended limit for daily sodium intake, they were quick to caution that it is still possible to consume too much sodium. This is especially true if you are not getting enough potassium and other nutrients from sources such as leafy greens, bananas, sweet potatoes, and berries. Nutrient balance matters, but as long as you consume a varied and healthy diet, you ahould
Important Note: The above should not be construed as medical advice. Contact your physician before starting any exercise program or if you are taking any medication. Individuals with high blood pressure should also consult their physician prior to taking an electrolyte supplement. Overdose of electrolytes is possible, with symptoms such as vomiting and feeling ill, and care should be taken not to overdose on any electrolyte supplement.
Jonathan Toker is a Canadian elite-level runner and triathlete. He received a Ph.D. in organic chemistry from The Scripps Research Institute in 2001, and raced in the professional ranks as a triathlete for 5 years and now mostly runs on trails. Dr. Toker worked as a scientist in the biotech industry for 5 years prior to launching his unique SaltStick Electrolytes and Dispensers lineup.
