April 24, 2013
Sodium intake (SI) is far beyond the normal recommended amounts in many countries. In an analysis (Medline ID: 20826631) of 38 studies between 1957 and 2003, it was determined that the US population drastically exceeds guidelines without any reduction over the years. This article examines the two primary claims surrounding sodium consumption:
1. Higher SI leads to increased mortality from cardiovascular disease (CVD), hypertension, metabolic syndrome, cancer, and other inflammation markers
2. Reducing SI leads to decreased mortality from CVD, hypertension, metabolic syndrome, cancer, and other inflammation markers.
Does Higher Sodium Intake Lead to Increased Mortality from CVD, Hypertension, Cancer, and other Inflammatory Markers?
A massive review (Medline ID: 10333851) of many (randomized) controlled trials reveals that there is insufficient evidence that the reduction of sodium intake for normal (non-hypertensive) people would provide any benefit.
The DRI report provided by the USDA says that sodium intake does indeed increase the risk for hypertension and thus stroke, coronary heart disease, heart failure, and renal disease. It goes on to acknowledge that modifications in SI and resulting risks are based on many variables including: age, gender, genetics, blood pressure, race, etc.
A Japanese study (Medline ID: 20016010) of nearly 80,000 men and women concluded that sodium intake as a whole does not increase risk for cancer, but may increase risk for CVD. Interestingly, salty foods do increase risk for cancer.
Another Japanese study (Medline ID: 18614741) of nearly 60,000 men and women with no history of stroke, heart disease, or cancer, concluded that a high SI and low potassium intake increases the risk of mortality from CVD.
A study (Medline ID: 18556187) of 766 subjects observed higher sodium levels in those with metabolic syndrome. A higher sodium level was also associated with obesity and high blood pressure. After adjustment for obesity, there was no association between sodium levels and blood pressure.
A randomized population study (Medline ID: 19386745) saw an association between sodium intake and inflammation markers, but suggests that this is due to body mass index. They conclude that evidence is weak for a causal relationship between SI and inflammation markers that lead to CVD and cancer.
Will Reducing Sodium Intake Lead to Decreased Mortality from CVD, Hypertension, Metabolic Syndrome, Cancer, and other Inflammation Markers?
A review (Medline ID: 21219163) of multiple studies concludes that the reduction of sodium intake in the general population would lead to a significant decrease in risk for CVD in a much more cost-effective way than normal intervention.
The same review listed above (Medline ID: 10333851) concludes that reduction of sodium intake is effective for hypertensive individuals.
A recent report (Medline ID: 20577156) by the CDC says the following: “Based on predictive modeling of the health benefits of reduced salt intake on blood pressure, a population-wide reduction in sodium of 1,200 mg/day would reduce the annual number of new cases of coronary heart disease by 60,000---120,000 cases and stroke by 32,000---66,000 cases.”
A review (Medline ID: 19768251) of 9 studies showed that sodium intake has an effect on insulin resistance, metabolic syndrome, blood pressure, and inflammation markers. Most studies showed benefits from moderate sodium restriction, but the authors claimed that more studies are needed.
A review (Medline ID: 19121772) of random controlled trials, including a meta-analysis, concludes that sodium restriction in hypertensive individuals reduces blood pressure, but not in normal individuals. The effect of long-term reduced SI on mortality from hypertension is unclear.
Seemingly there has yet to be studies which can directly link sodium intake as a cause for hypertension, cancer, CVD, metabolic syndrome, and other inflammation markers. The associations which were found are likely due to an obesity factor. Many foods that are high in sodium, such as processed foods, are also very high in calories and trans fats. Restricting sodium for hypertensive individuals may be an effective treatment however encouraging people to lose weight should have a larger impact on mortality from the above conditions.