RENAL ROTATION: Understanding Calcium Imbalances
In this blog post you will have the chance to review all the things about calcium and chronic kidney disease (CKD) that you may have forgot about from your MNT and micronutrient metabolism classes.
First we’ll review the relationship between calcium and the kidneys. Then discuss when you should be concerned about your patient’s calcium levels and how to go about discussing these concerns with your patient. Then, review the sources of calcium your patients should know about so they have a better understanding of how their diet and treatment impacts their overall calcium balance.
Let’s get started.
Calcium and the Kidneys
When Calcium Levels are LOW
The kidneys play a role in maintaining electrolyte balance, including calcium. When calcium levels are low, the parathyroid gland releases parathyroid hormone (PTH) which tells the kidneys to produce more calcitriol, the active form of Vitamin D.
Calcitriol acts in two ways to increase calcium levels (1):
signals the kidneys to reabsorb calcium
signals the gut to produce more calcium transport proteins which then increases absorption of calcium
When Should I be Concerned About My Patient’s Calcium Levels
As we just reviewed, declining kidney function can affect calcium balance. Studies have shown that patients with low calcium levels and CKD will develop kidney failure sooner than patients with normal calcium levels (3). So, if you have a patient with CKD, it’s important to keep an eye on their calcium levels especially as their condition progresses.
Negative Calcium Balance
Negative calcium balance can occur when dietary intake can’t keep up with the amount of calcium loss despite the body’s best efforts to increase calcium levels (i.e. the release of PTH).
Since 99% of calcium is stored in our bones and teeth a negative calcium balance can lead to mineral bone disorder, osteoporosis and an increased risk of fractures (4, 5).
Positive Calcium Balance
A positive calcium balance can occur if calcium intake exceeds the kidney’s ability to excrete it fast enough. High calcium levels can be related to consuming excessive amounts of calcium through the foods they eat or with supplements (4). An excess amount of vitamin D supplements can also increase calcium levels (6).
A positive balance of calcium can increase the risk of heart attacks, stoke, and calcification of heart valves (4, 7).
How do I Discuss These Concerns with My Patient
STEP 1: Review lab results
If the patient is newly diagnosed with CKD, reviewing labs may be a bit overwhelming. Even if your patient was been diagnosed with CKD years ago or has undergone multiple dialysis treatments, you may still need to explain the labs like it’s their first time.
Labs can be complicated and if your patient is experiencing symptoms related to their CKD it can be difficult to focus. So it’s important to keep it simple and to the point when discussing labs with your patient.
If the patient is in early stage of CKD you may focus mainly on the abnormal labs and briefly discuss labs that are within normal limits. However, if the patient is in a more advanced stage of CKD or undergoing dialysis treatment you may review ALL the labs with the patient on a regular basis to show them how their treatment is going and how their diet may or may not be impacting their blood levels.
Depending on the stage of CKD, patients will get their labs draw annually to as frequent as every three months or before and after every hemodialysis treatment.
As if related to calcium related labs, you’ll likely focus on corrected serum calcium, PTH-intact, and phosphorus levels with the patient. Each of which you can go into brief detail about the function of each and how they interact with one another. Again, the level of detail you review with the patient may depend on how alter or focused they are during your nutrition consult session.
** Note that there are other medical conditions that can affect these lab values such as hyperparathyroidism, elevated Vitamin D levels, dehydration, and certain types of cancer (1).
STEP 2: Discuss risks associated with abnormal calcium levels
Having an open discussion with your patient about the risks associated with their abnormal calcium levels gives them the knowledge to help them make informed decisions about their health.
If there calcium levels are trending down or have been consistently low you can discuss the risks of low calcium which can then lead into the conversation about the foods and possibly supplements that can help bring their levels back to a level that is acceptable or normal for their condition.
If calcium levels are trending upwards or are consistently elevated, you can discuss the risks of high calcium levels then lead the conversation into dietary recommendations and foods to avoid until levels return back to normal for their condition.
STEP 3: Review dietary recommendations
You’ve reviewed the labs, explained why it’s important to maintain normal levels. Now you discuss dietary intake recommendations that can help bring them back to normal levels. Dietary intake recommendations for kidney disease are slightly different than individuals with healthy kidneys.
Calcium intake recommendations for adults with CKD ranges from 800 to 1,000 mg/day and not to exceed 1,500 mg/day (8). Though the National Kidney Foundation recommends that total calcium intake does not exceed 2,000 mg/day in patients with renal disease (9).
As you’re discussing dietary recommendations with your patient, this is a great opportunity to transition into the different sources of calcium before discussing the patient’s overall calcium intake goals to help return calcium levels back to levels for are appropriate for their condition.
Sources of Calcium that Your Patients Should Know
Review the sources of calcium your patients will help them have a better understanding of how their diet and treatment impacts their overall calcium balance and help them make informed decisions about their overall health.
Calcium Containing Foods (10): When speaking to patients about sources of calcium it’s important to note that foods high in calcium can also be high in phosphorus. If you’re concerned about your patients phosphorus levels, you may have to recommend avoiding or limiting calcium containing foods that are high in phosphorus. Patients may also be prescribed a phosphate binder to help reduce phosphorus levels.
Phosphate binders (11): Certain types of phosphate binders contain calcium - this included calcium carbonate and calcium acetate. A physician may recommend a calcium containing phosphate binder if calcium levels are low, or switch to a calcium-free phosphate binder if calcium levels are high.
Dialysate (12, 13 ): The dialysate solution used in dialysis treatment contain calcium as well as other electrolytes. Calcium concentrations can vary by patient and treatment. Calcium concentrations in dialysate can be as low as 1.5 mEq/L or even as high as 3 mEq/L depending on the patients needs.
Supplements (9, 14): It’s important to note any and all supplements that the patient is taking including protein powders, herbs, minerals, etc. as some may contain calcium or other nutrients that are not appropriate for kidney disease. There are times that supplements may be deemed appropriate. For instance, if calcium levels are low, patients may be prescribed a calcium supplement or a vitamin D supplement to help increase calcium absorption.
* This blog is for educational purposes only and shall not be taken as medical advice. *
