As a kidney doctor, I can’t tell you the number of times a patient has told me that they were told to avoid eating plant-based foods by somebody else. Sometimes it’s because of the phosphate content of these foods. Other times it’s because of the “sugar.” But often it’s because of the potassium. In the same breath (or should I say bite?), patients tell me that they have been told to eat more meat because their kidney disease requires them to consume more protein. Although a few patients might have medically-justified reasons for limiting certain plant foods, many patients might benefit from doing the exact opposite: eating more plant-based foods and less animal-based foods. Time and time again, plant foods are beneficial for the body and it should come as no surprise that there is growing evidence for their use in kidney disease.
Any discussion of the prevention and treatment of kidney disease requires a quick primer in the field. Chronic kidney disease, or CKD, is an umbrella term for any sort of dysfunction of the kidney, irrespective of cause. The phrase “chronic kidney disease” is often accompanied by a number after it, ranging from 1 to 5, indicating the severing of the disease (stage 5 being the worst). Approximately 1 in 3 Americans are at risk for developing it and 1 in 7 already have it. The reason CKD is so common is because the causes for it – namely diabetes and high blood pressure – are even more common. Diabetes is the most common cause of kidney failure (also known as CKD 5 or end-stage renal disease) in America, with high blood pressure (or hypertension) not far behind. Fortunately, in most cases, both diabetes and hypertension are often not only treatable but preventable.
However, too few people know that their diseases can be reversed, and their CKD need not progress to the final stage of the disease, which requires dialysis (a machine to filter the blood) or a transplant. Nearly 90% of people who have CKD don’t even know they have it, which is why it is so important to see a physician regularly and to have blood work done, especially if you have diabetes or hypertension or at risk for either of those diseases. A whole-foods, plant-based (WFPB) diet that is rich in fruits, vegetables, legumes, and whole grains will help you lose weight and help your body metabolize glucose more efficiently, both of which ultimately help treat – and even reverse – type 2 diabetes (the type caused by lifestyle whereas type 1 diabetes is an autoimmune disorder). As I’ve told countless of patients, although fruits contain “sugar,” they also contain fiber, which helps slow down the absorption of the sugar – so much so that diabetics eating fruits do better than those who don’t. The danger is in eating a vegan diet that isn’t healthy, like Oreo cookies or french fries all day. The key is to eat a healthy vegan diet.
The beauty of this type of diet is that it also prevents and treats other diseases like high blood pressure, which is the second most common cause of kidney failure in Americans. A WFPB diet is low in sodium and high in potassium – both of which help to reduce blood pressure. It can also help you lose weight, which is important because weight loss directly lowers blood pressure. Even the basic building blocks, or amino acids, found in animal protein have been shown to raise blood pressure when compared to those found in plant proteins. When researchers have looked at blood pressure in modern societies, they often find that those eating a healthy vegan diet have the lowest blood pressures of all the people in the study.
Okay doc, you’ve convinced me that eating a WFPB can prevent and treat type 2 diabetes and hypertension, thereby preventing kidney disease, but what if I already have it?
If you already have kidney disease, it is not too late to start eating a WFPB as CKD may be progressive, meaning that your kidney function can decrease with time even if your diabetes or high blood pressure is reasonably controlled. Even with the best of medications, the mere presence of diabetes and high blood pressure can take a toll on the kidneys in some (but thankfully not all) people.
If you already have kidney disease, a plant-based diet can also be directly beneficial to the kidney and your health in other ways. For example, the diet can change your microbiome to what many researchers believe is a healthier microbiome – one that is filled with bacteria that digest carbohydrates as opposed to meat, which has been shown to reduce general inflammation. The diet can also reduce levels of TMAO, a toxic compound produced by bacteria in the gut after ingestion of meat or dairy leading to heart and kidney disease, and even death.
A WFPB can also reduce the amount of phosphorus levels in the blood because most of the phosphorus in plant foods is in a non-absorbable form. Lower phosphorus levels are important in controlling some of the more deleterious effect of CKD, like calcification of the blood vessels and progression of CKD. Animal-based and processed foods have phosphorus that are more readily absorbable – and in some cases 100% absorbable – making it difficult to control the level in the blood.
Another important benefit of plant foods is that they are naturally alkaline because kidneys lose the ability to reduce acid levels in the blood in CKD. As such, many patients with CKD often have high levels of acid in their blood requiring – none other than – baking soda to neutralize the acid levels. Researchers have shown that the same benefit of neutralizing acid levels can be achieved by just eating more fruits and vegetables, which are naturally alkaline. Too much acid in the blood can lead to weakened bones (bones are the body’s natural buffer to acid in kidney disease) and further loss of kidney function.
But what about getting too much potassium or not enough protein when eating a whole-foods, plant-based diet?
Researchers have shown that those eating a plant-based diet in CKD get enough protein to meet their daily needs, especially when eating a diet from a variety of sources (one that includes different type of plant-based foods and not just apples by themselves all day, for example). In fact, eating too much protein while having CKD is thought to worsen kidney disease, which can happen more readily in those eating protein-dense, animal-based diets. On the contrary, plant-based diets have enough protein to meet daily demands but not so much as to put one at risk for more kidney disease.
Although plant foods do contain potassium, they also contain substances that help reduce the rise in potassium levels in the blood. High levels of potassium in the blood can stop the heart from beating correctly, causing death. However, not everyone who eats plants gets high potassium levels. Why? Plant foods contain fiber which helps increase the size and frequency of bowel movements, which is important in helping you get rid of potassium Every time you have a bowel movement, you lose potassium, which helps to balance against rise in potassium in the blood. Plant-based foods also improve sugar and acid levels in the blood, which can also reduce potassium levels in the blood. Also, not all plant-foods are not created or prepared equally. For example, eating a medium sized orange has less potassium than drinking a cup of orange juice, which takes two to four oranges to make. For that reason, fruit juices and vegetables sauces (like tomato sauce/paste) can easily increase potassium levels for patients with kidney disease. Potatoes and beets are also unusually high in potassium compared to other plant foods and should not be eaten in excess, at least until more research is done. But non-dietary factors can also affect potassium levels. Many of the medications that patients with kidney disease take can raise levels of potassium leaving little room for error, like beta-blockers (e.g. metoprolol) or ACE-inhibitors/ARBs (e.g. lisinopril or losartan). It is for these reasons that all patients with CKD or at-risk for having CKD should be supervised by a physician with monitoring of their blood work while incorporating plant-based foods to their diet to avoid dangerous potassium levels. Some people will only need minor changes to their medication regimen or diet while others will tolerate the changes without incident. A select few will not be able to tolerate the changes and will need to work with a dietician or physician to make additional changes.
Although potassium levels are a cause for concern, they do not universally preclude the use of plant-based diets in patients with CKD. In fact, many patients are not only able to tolerate the transition but benefit from it by treating their diabetes, high blood pressure, chronic kidney disease, and other complications of CKD (like acidosis and high phosphate levels). Plant-based diets have been so beneficial in other areas of health, like heart disease and cholesterol, that it doesn’t come as a surprise that they can have benefits to those with – and at-risk for developing – kidney disease.
Shivam Joshi is a nephrologist and internal medicine physician practicing in New York City. You can follow him on Twitter and Facebook as sjoshiMD.