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Creatinine

CREATININE

(S-CR)Creatinine (Cr) is a waste product created during the use of creatine phosphate in muscle energy production. Creatinine is constantly removed from the body via kidneys by filtering it into the urine. Due to this, the creatinine levels in the serum are crucial when assessing kidney function. Proper kidney function is critical in waste product removal as well as red blood cell production, bone metabolism, and the regulation of blood pressure and fluid balance.

The creatinine levels of healthy individuals are in proportion to their muscle mass and protein intake. High levels indicate impaired kidney function that may be caused by various reasons. These include infections, autoimmune diseases, kidney inflammation, kidney stones, urinary tract obstruction, and certain medications such as ACE inhibitors. If the creatinine levels are high, a new blood test should be completed to confirm the result. Even slightly elevated creatinine levels can indicate severe kidney damage or disease. Consistently high creatinine levels require medical treatment and follow-up tests.


Low creatinine levels can indicate a low body muscle mass or protein intake. Insufficient creatinine levels are linked to increased mortality and lower survival rates, particularly for hospitalized patients. Such cases usually involve cachexia, a significant loss of muscle protein.


Slightly elevated levels occur particularly in men with a large muscle mass and high protein intake from food, as well as generally in connection with dehydration, without indicating a pathological change. In such cases, the cystatin-C marker is more precise in assessing kidney function.


Approximately 10 % of the world population has a chronic kidney disease of some type. The two main risk factors for kidney deficiency are high blood pressure and hypertension as well as diabetes.


Typical reference range (S-Cr):

  • Men: 60–100 umol/l
  • Women: 50–90 umol/l

Lifestyle factors improving kidney function include:

  • Avoiding (or quitting) smoking
  • Moderate exercise that strengthens the circulatory system
  • Sufficient fluid intake
  • Good control of blood sugar and avoiding diabetes
  • Maintaining normal body weight
  • Maintaining normal blood pressure level

In healthy individuals, a high-protein diet is not harmful to the kidneys. However, in individuals already suffering from kidney deficiency, restricting protein intake reduces the stress placed on the kidneys and alleviates the deficiency. In fact, protein has been found to lower blood pressure and thus ease the stress placed on the kidneys.


When improving kidney function through nutrition, the focus is on an anti-inflammatory and nutrient-rich diet. Keeping the intestines in good condition is also important for kidney function—in particular, the leaky gut syndrome may cause toxins to be released into the circulation, potentially causing kidney damage. Studies have found that a pro-inflammatory diet, such as SAD (Standard American Diet), significantly impairs kidney function.


In the event of impaired kidney function, it is recommended to (at least temporarily) limit sodium, potassium and phosphorus intake from food.


Foods and supplements that support kidney function include:

  • Flavonoid-rich foods in general support kidney function
  • Blueberries (rich in anthocyanins)
  • Cranberries (improve the condition of urinary tracts and ureters and inhibit infections)
  • Alkaline foods such as vegetables, berries, and fruits (a high dietary acid load impairs kidney function)
  • Resveratrol (animal tests have found it to reduce inflammation and oxidative stress in the kidneys)
  • Dandelion
  • Curcumin
  • Nettle (lowers blood pressure and acts as a diuretic)
  • Silybum marianum (Milk thistle)
  • Reishi (animal tests have found it to inhibit kidney damage)
  • Schisandra (five-flavor berry) (findings from animal tests)
  • Lemon juice (inhibits the formation of kidney stones)
  • Vitamin C (human and animal tests have found it to protect kidneys in connection with kidney disease)
  • Excessive vitamin C use may be a predisposing factor for kidney stones (at least in men)
  • Antioxidants, in general, may be helpful in early stages of impaired kidney function
  • Kidney deficiency causes impaired nitric oxide (NO) production; therefore, NO production-boosting foods (and amino acids) may help improve kidney function
  • Beetroot
  • Arginine
  • Citrulline malate