Do Not Ignore Micronutrients in Low-Protein, Plant-Based Diets in CKD – Renal and Urology News

Low-protein, plant-based diets are gaining traction in the chronic kidney disease (CKD) community as a therapy to slow progression of kidney disease.  As with any new and emerging therapy, it is important to consider any potential negative side effects, however unintentional, if the therapy is to be improved. Several studies have examined the risk of protein malnutrition in low-protein, plant-based diets in CKD and demonstrated that protein malnutrition can largely be prevented with careful oversight by a dietitian as well as the use of ketoanalogues.¹ However, micronutrient deficiency seems to be largely unexplored. Micronutrient deficiencies can lead to serious complications in patients with CKD and potentially limit the effectiveness of low-protein, plant-based diets.  Assessing for micronutrient deficiencies is a key factor in ensuring that dietary interventions support overall health, not just maintaining specific mineral balances to prevent kidney-related complications.

There can be nutrient deficiencies with any diet: vegan, omnivore, gluten-free, high-protein, low-protein, and others. Some diets may naturally be higher or lower in certain nutrients and may necessitate more focus. This should be considered in addition to potential risk factors and increased or decreased needs an individual may have based on disease conditions, medications, micronutrient deficiencies, and symptoms. 

An example of a micronutrient to consider in patients with CKD on a low-protein, plant-based diet is zinc. Studies show that zinc levels tend to be lower in those with CKD, and low zinc levels are a risk factor for kidney failure and cardiovascular disease.² Multiple studies show that plant-based diets (ie, vegetarian or vegan diets) can be 43%-54% lower in zinc compared with an omnivore diet.³ It is also important to consider that zinc (and many other minerals) have reduced bioavailability from plant-foods, anywhere from 5%-50%.⁴ Zinc deficiency symptoms include poor wound healing, reduced appetite, hair loss, loss of taste, diarrhea, nausea, and depression. These symptoms are also commonly associated with CKD in general, but zinc status is not often assessed.⁵ This article cannot review all the micronutrient considerations, but illustrates a point that interventions without appropriate oversight and full consideration of the impact of micronutrients can contribute to other problems that may be overlooked because they are common in CKD.

An additional challenge is that micronutrient recommendations for those with CKD, let alone considering therapeutic diets, are unclear. This is likely due to several reasons. Many of the human studies of dietary interventions in CKD are conducted over a short period of time, a matter of weeks to just over a year. Additionally, many studies have not assessed micronutrient status before and after dietary changes. This may be because, generally speaking, the assessment of nutrition is challenging to begin with, and there is a scarcity of data with regard to micronutrient estimated needs in those with CKD.  Currently, Dietary Reference Intakes (DRIs) are the most common recommendation for nutrient goals for patients with CKD, even though an Institute of Medicine DRI reference specifically states, “A requirement is defined as the lowest continuing intake level of a nutrient that will maintain a defined level of nutriture in an individual…It was beyond the scope of the report to consider the use of nutrients in the treatment of disease or other disorders.”⁶ Providers are in a difficult position given that the DRIs are not appropriate for patients with CKD and research does not provide clear recommendations.

Still, to support a healthy micronutrient status in patients with CKD, clinicians can:

1. Ensure any patient following a therapeutic diet (such as a low-protein, plant-based diet) has the support of a trained renal dietitian.
2. Encourage regular food tracking so that a patient’s nutrient intake can be estimated and compared with their estimated nutrient requirements.
3. Regularly assess for nutrient deficiencies, which are easy to miss if no one looks for signs and symptoms. Regular assessment can be done by any health care professional trained in looking for signs and symptoms of nutrient deficiencies, especially for patients at increased risk for them.
4. Consider micronutrient testing, keeping in mind that serum levels may not always be accurate, so functional micronutrient testing may be more appropriate.  (Labs such as Genova Diagnostics, SpectraCell, Vibrant America Labs or Cell Science Systems are available options.)
5. Be willing to use supplements. Most people need some supplements to fill in dietary gaps. There are many considerations and options available. Providers who have not had extensive training on the use of supplements can collaborate with those who have to ensure that quality supplements are used judiciously. 

Micronutrients are key for any biochemical pathway to function properly. While a low-protein, plant-based diet can support kidney health, in the long term, without the support of adequate micronutrients, the benefits are likely to be short-lived.  As more research emerges, providers can provide more targeted approaches to micronutrient management, but until then providers can use the variety of tools available to create a supportive body of practice-based evidence.

Lindsey Zirker MS, RD, is a renal dietitian and Director of Clinical Services for the Kidney Nutrition Institute in Titusville, Florida. She specializes in autoimmune kidney disease and advanced practice medical nutrition therapy for people with kidney disease. 

References

1. Molina P, Gavela E, Vizcaino, Huarte E, Carrero J. Optimizing diet to slow CKD progression.  Front Med. 2021. Doi:10.3389/fmed.2021.654250
2. Tokuyama A, Kanda E, Itano S, et al. Effect of zinc deficiency on chronic kidney disease progression and effect modification by hypoalbuminemia. PLoS One. 2021;16(5):e0251554. doi:10.1371/journal.pone.0251554
3. Tso R, Forde CG. Unintended Consequences: Nutritional impact and potential pitfalls of switching from animal- to plant-based foods. Nutrients. 2021;13(8):2527. doi:10.3390/nu13082527
4. National Institutes of Health. Zinc. Fact Sheet for Health Professionals.
5. Kopple JD, Massry SG, Kalantar-Zadeh K, Fouque D. Nutritional Management of Renal Disease. 4^th ed. Academic Press; 2021.
6. ‌National Academies of Sciences, Engineering, and Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press.