Microalbuminuria And Sodium

High potassium foods are characterized by a high ratio of potassium to sodium. There have been many studies showing the strong preventive relationship between high potassium foods and hypertension, strokes, cardiovascular disease, and osteoporosis. However there are a number of other diseases that also may be related to a poor potassium sodium ratio. An early marker for several of these diseases is moderately increased albumin (a normal blood protein) in the urine. This increased albumin in the urine is an early sign of damage to blood vessel lining cells. Damage to the blood vessel lining cells in the kidney results in leakage of albumin into the urine from the blood vessels as the blood is filtered. This moderately increased albuminuria is also called microalbuminuria. It occurs in 5 to 14% of the general population. There are several conditions that lead to it. Two common conditions leading to microalbuminuria are diabetes and hypertension. In these two conditions, microalbuminuria is an important risk factor for progression toward worsening cardiovascular and kidney damage.

Microalbuminuria And Sodium

Glomerulus
Glomerulus (where blood filtering begins in kidney)
Some recent studies of the association of sodium and microalbuminuria have been done, one of which was published in 2014 (1). Prior published studies had smaller numbers of participants, but showed a positive association of sodium and microalbuminuria. This study was based on a national survey, the Korea National Health and Nutrition Examination Survey (KHANES). The researchers looked at the records of over 5100 participants. They found a positive association of sodium intake with albumin in the urine.

In this study and in other studies, the association of sodium and microalbuminuria did not depend on increased blood pressure. Some animal and human studies indicate the damage to the kidney is independent of blood pressure. Inflammation appears to be involved. Other researchers have found a raised level of an inflammatory marker in the blood, and another set of researchers has found scar tissue (fibrosis) in the kidney when there is albuminuria and a high salt intake.

There were multiple other associations with sodium also found in this study. These are all diseases which would be associated with aging. The researchers then corrected for the associated problems and still found an independent association of increased sodium intake with microalbuminuria.

The Findings

The researchers collected urine samples from the participants and estimated sodium intake from urinary sodium. They divided the group into 4 separate groups according to the estimated sodium excretion per day. They found a high association of increased albumin in the urine with increased salt excretion.

However, they found a number of other associations also. They found an association with age. In the group with the lowest sodium excretion there was an average age of only 45. The group with the highest sodium excretion was older with an average age of 58.

They also found an association of sodium excretion with gender. The group with the lowest amount of sodium excretion had fewer females than the group with the highest sodium excretion.

They also found that waist circumference went up as sodium excretion went up. And the Body Mass Index (BMI) increased in a similar fashion. The percentage of people who were obese in the group with the lowest sodium excretion was 28%. The percentage who were obese in the highest quartile was 38%.

They also found a strong association of sodium excretion with systolic and diastolic pressure. And likewise there was an association with serum triglycerides.

Adjustments

Because of these other associations, the researchers adjusted for age, gender, diabetes, hypertension, and obesity. They used 3 models. The 1st model had no statistical adjustments to the data. In this model there was an extremely high correlation between urinary sodium excretion and albuminuria.

The second model adjusted for age and gender. It also had a high correlation of salt intake and microalbuminuria.

In the third model, the researchers adjusted for age, gender, diabetes, hypertension, and obesity. This model continued to have a highly significant association. So the association of microalbuminuria with sodium is independent of these other factors that are also associated with sodium.

Limitations

The study was a simple cross-sectional study. The researchers simply took a cross section of the population, divided them according to sodium intake, and compared the groups to each other. Because of this design of the study, they were not able to determine causality.

Additionally, there are other limitations to the study. The researchers went unable to obtain the drug history. So some participants may have been on diuretics or other medications affecting the urinary sodium and albumin excretion.

And another limitation is that the researchers used a single spot collection of urine instead of a 24 hour collection. These collections are known to have highly variable sodium content with a low correlation to the day's sodium intake.

Nonetheless this was an early study that shows potential kidney damage from a high sodium intake. It indicates that more studies should be done on the role of excessive sodium in kidney damage.

A poor potassium sodium ratio affects every cell in the body. Either too much sodium or too little potassium will result in a poor potassium sodium ratio. The researchers did not examine potassium in this study, so the correlation of the potassium sodium ratio with microalbuminuria could not be done. But such a study is needed.
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1. Association of the estimated 24-h urinary sodium excretion with albuminuria in adult koreans: the 2011 Korea National Health and Nutrition Examination Survey. Han SY, Hong JW, Noh JH, Kim DJ. PLoS One. 2014 Oct 14;9(10):e109073. doi: 10.1371/journal.pone.0109073. eCollection 2014.