Humanity likes a good villain; someone to blame for the problem. Knowing who to hate and what to fight seems important. This is especially true when it comes to our health. One villain per disease makes healing feel achievable. When it comes to heart disease it’s cholesterol. With diabetes it’s sugar. And hypertension? Salt of course!
Hypertension is often blamed on excess salt in the diet. However, not all blood pressure is affected by salt intake. Salt sensitivity of blood pressure (SSBP) does exist and is an independent risk factor for cardiovascular disease and death. It’s estimated that more than 50 percent of hypertension cases are salt sensitive. It also affects a quarter of individuals with normal blood pressure in the United States and manifests in other ways.
I believe one reason salt has become a problem is the all-too-common state of insulin resistance. Insulin resistance is present in type 2 diabetes, metabolic syndrome, pre-diabetes, polycystic ovary syndrome (PCOS), often in type-1 diabetes and elevated cholesterol, and hypertension. Insulin resistance results in higher insulin levels, either naturally occurring or injected. This elevated insulin decreases the excretion of sodium in the urine, which is a primary way we eliminate sodium from the blood other than through sweat. As a result, the kidneys retain more salt. So insulin resistance basically impedes our ability to tolerate salt.
“Research in the last three decades has proved a strong association between hypertension and insulin resistance, and this relationship is stronger in salt sensitive hypertension.”1 Interestingly, in those who are salt sensitive, high salt intake may exacerbate insulin resistance. “In turn, insulin resistance seems to heighten the blood pressure response to sodium intake.”2 In other words, individuals with insulin resistance are more likely to experience hypertension, and this is compounded if they are salt sensitive and consuming a lot of salt.
High salt intake seems to make insulin resistance worse. However, this is not true across the board. In fact, some research indicates that insufficient sodium promotes insulin resistance. Some studies have found that blood glucose levels in in the low-salt intake group were significantly higher than those in the normal or high-salt intake groups.3 Whoa!
Research with sodium and osteoporosis is mixed, as well. While some research shows excess excretion of calcium in the diet with high salt intake, sodium was not associated with change in bone mineral density in post-menopausal women.4 In addition, some research found “that decreased dietary salt intake was significantly associated with the development of osteoporosis.”5 They observed that a low sodium diet activates the renin-angiotensin-aldosterone system (RAAS) which stimulates osteoclast formation and inhibits osteoblast activity promoting osteoporosis. Osteoclasts break bone down, while osteoblasts build bone. The researchers concluded that consuming less than 2,000 mg/day was an independent predictor for increased risk of osteoporosis.
Sodium is actually vital for body function. It is not a clear-cut enemy. What is the solution to something that may not be as absolute as we thought? With no villain, how do we know what our stance should be?
The context of the amount of salt we consume is an important variable in determining if the sodium will do more harm than good. Discussion on how to be safely and healthfully salted will be our topic next month.
In summary:
- This is not a comprehensive discussion on salt.
- Not all people are salt sensitive and require dramatic restriction of salt in the diet.
- Knowing if you are salt sensitive is important. Restrict sodium to 2,000 mg/day and see if blood pressure number lowers 10 points to determine if salt restriction is going to help.
- Insulin resistance can make us unable to tolerate as much salt in the diet.
- Low salt intake has been associated with higher blood glucose levels and osteoporosis in some individuals.
- Ertuglu, L. A., Elijovich, F., Laffer, C. L., & Kirabo, A. (2021). Salt-Sensitivity of blood pressure and insulin resistance. Frontiers in Psychology, 12. https://doi.org/10.3389/fphys.2021.793924
- Ibid.
- Shen, Y., Shi, Y., Cui, J., He, H., & Ren, S. (2023). Effects of dietary salt intake restriction on blood glucose levels: a meta-analysis of crossover study. Nutrition Research and Practice, 17(3), 387. https://doi.org/10.4162/nrp.2023.17.3.387
- Carbone, L., Johnson, K. C., Huang, Y., Pettinger, M., Thomas, F., Cauley, J., Crandall, C., Tinker, L., LeBoff, M. S., Wactawski-Wende, J., Bethel, M., Li, W., & Prentice, R. (2016). Sodium intake and osteoporosis. Findings from the Women’s Health Initiative. The Journal of Clinical Endocrinology & Metabolism, 101(4), 1414–1421. https://doi.org/10.1210/jc.2015-4017
- Hong, S., Choi, J. W., Park, J., & Lee, C. H. (2022). The association between dietary sodium intake and osteoporosis. Scientific Reports, 12(1). https://doi.org/10.1038/s41598-022-18830-4
