Your kidneys hold about 2 million tiny filters, and a filter that scars does not grow back. In one small trial, cutting salt for two weeks halved the protein leaking from damaged kidneys, and in another it worked more than twice as well as adding a second blood pressure pill. Here are five daily habits that may take pressure off your kidney filters, what the research found for each, and which two tests show whether they are working. (Based on the insights of Dr. Sean Hashmi)
Key Takeaways
- In a small crossover trial of 20 people with stage 3 to 4 kidney disease, two weeks of low sodium (about 1,700 mg/day) halved the protein leak and lowered blood pressure; it did not measure eGFR.
- A second trial found cutting salt reduced the protein leak by 51% versus 21% for adding a second blood pressure pill. The guideline target for kidney disease is under 2,000 mg of sodium a day.
- Sweet drinks, plant versus animal protein, post-meal walking and 7 to 8 hours of sleep were each linked with lower kidney strain or risk, though many of these findings are observational.
- In a year-long trial of 631 people with stage 3 kidney disease, extra water did not slow kidney decline; kidney stones are the exception, and fluid limits should be followed.
- Track eGFR (under 60 for 3 months or longer indicates kidney disease) and UACR (under 30 mg/g is normal), and check with your care team before changing diet, fluids or medicines.
Why Pressure Inside The Kidney Filters Matters
Your two kidneys hold about 2 million tiny filters, and a filter that scars does not grow back. When the pressure inside a filter stays too high for too long, it starts leaking protein, then scars, and finally stops working. Kidney function is lost one filter at a time. That pressure also shifts every day with what you eat, what you drink, how much you move and how long you sleep.
One clarification on the idea of improving kidney function in two weeks: the short trial described below measured protein leak and blood pressure, not eGFR. These habits are supportive steps that may take pressure off your filters, and they do not replace medical treatment.
Habit 1: Cut Your Sodium
The international kidney guideline sets a limit of under 2,000 mg of sodium a day for people with kidney disease. The average American eats about 3,400 mg. Salt pulls extra fluid into the blood and raises blood pressure, which pushes up the pressure inside the filters.
In a small crossover trial, 20 people with stage 3 and 4 kidney disease and high blood pressure spent two weeks eating about 3,900 mg of sodium a day and two weeks eating about 1,700 mg. On the low-salt weeks, systolic blood pressure dropped by about 10 points and diastolic by about 4, and the protein leaking into the urine fell by half.
In a second trial, people with kidney disease who were already on the top dose of lisinopril were given either a second blood pressure pill or a low-salt diet. The second pill cut the protein leak by 21%, while cutting salt cut it by 51%, even though the diet only brought people down to about 2,400 mg of sodium a day. These were small, short trials, but they suggest salt can matter a lot.
- Look at packaged foods. More than 70% of the sodium Americans eat comes from packaged and prepared foods, not the salt shaker.
- Read the label. A food with 5% of the daily value or less per serving is low in sodium, and 20% or more is high.
- Cook at home more and use garlic, onions, lemon, black pepper and herbs for flavor.
Taste adapts: in one study, people who cut their salt for five months came to prefer less salt in soup and crackers. Do not stop or change a blood pressure medicine on your own. If you take diuretics, have low blood pressure or have been given a fluid or salt plan, check with your care team before making big changes.
Habit 2: Drop The Sweet Drinks
Sugar also raises pressure inside the filters. A sugary drink hits the blood fast and prompts a surge of insulin, and insulin tells the kidneys to hold on to salt. In a small physiology study, raising insulin within the normal range in healthy adults cut the amount of salt their kidneys excreted by more than half.
High blood sugar adds a second problem. The kidneys pull extra sugar back into the blood with a pump that drags salt back in with it. Less salt then reaches the kidney’s salt sensor, which reads the filter as underworking and opens the gate wider, raising pressure inside the filter. Kidney doctors call this hyperfiltration. SGLT2 inhibitors, a newer class of prescription medicines, block that pump, and in an eight-week study in people with type 1 diabetes and overworked kidneys, filtration fell by about 20% back toward normal. Never start or stop such a medicine without your doctor.
Sugary drinks also raise the risk of type 2 diabetes. In a pooled analysis of more than 310,000 people, those who drank one to two sugary drinks a day had a 26% higher risk of type 2 diabetes than those who almost never did. This was observational, so it shows an association. About four in ten adults with diabetes have kidney disease.
Consider swapping soda, sweet tea, juice, sports and energy drinks and sweetened coffee drinks for water, sparkling water, unsweetened tea or black coffee, and eating fruit whole instead of drinking it. If you use insulin or medicines that can cause low blood sugar, keep treating lows the way your doctor advised.
The Extra-Water Myth
Many people are told that drinking lots of extra water is the best thing for the kidneys. In a trial of 631 people with stage 3 kidney disease, half were coached to drink more water for a year and drank about two and a half extra cups a day. After a year, they lost kidney function just as fast as those who drank their usual amount. A reasonable approach is to drink enough to keep your urine pale yellow, and to put your effort into the habits that move your kidney numbers.
Kidney stones are the exception. In a five-year study that followed people after a first kidney stone, drinking plenty of water cut repeat stones by more than half. If you have a fluid limit, keep to it.
Habit 3: Make Plants Your Main Protein
Protein from meat makes the filters work harder for hours after a meal. In one study, a meat meal made the kidneys filter about 16% harder, while the same amount of protein from soy left filtration unchanged. When healthy people ate mostly animal protein for three weeks, their kidneys let through almost twice as much albumin (a protein that should stay in the blood) as when they ate mostly plant protein.
In an observational study that followed almost 12,000 Americans for 23 years, those who ate the most red and processed meat had a 23% higher risk of kidney disease. Those who ate the most beans, peas and lentils had a 17% lower risk, and those who ate the most nuts had a 19% lower risk. Observational findings cannot prove cause and effect.
Plants may help kidneys that are already damaged too. In a three-year study of 108 people with stage 3 kidney disease, adding fruits and vegetables slowed the fall in kidney function compared with usual care. Fruits and vegetables lower the acid load the kidneys must clear, and across 14 studies in people with kidney disease, adding fiber lowered urea and creatinine.
You might build meals around beans, lentils, tofu, tempeh, edamame and nuts, and fill half your plate with vegetables. If your doctor has told you your potassium runs high, ask which plant foods fit your lab numbers. People with kidney disease should coordinate big diet changes, including potassium, phosphorus and protein, with their care team or a kidney dietitian.
Habit 4: Walk For 10 Minutes After Meals
After a meal, your leg muscles pull sugar out of the blood, so your body needs less insulin. In a study of 41 adults with type 2 diabetes, a 10-minute walk after each meal lowered after-meal blood sugar more than one 30-minute walk a day, and after dinner the rise in blood sugar was 22% smaller. Lower blood sugar and lower insulin mean your kidneys hold on to less salt, so the filters do less work.
In an observational study of more than 6,000 people with stage 3 to 5 kidney disease, those who walked for exercise were 21% less likely to need dialysis or a transplant and 33% less likely to die during the study. Those who walked five or more times a week were about 43% less likely to need dialysis or a transplant. Because this is observational, healthier people may simply walk more. If you have heart disease or trouble with mobility or balance, ask your doctor what is safe for you.
Habit 5: Sleep 7 To 8 Hours
Your kidneys run on a body clock, and sleep helps set it. While you sleep, blood pressure should normally drop by at least 10%, which gives the filters a break from pressure. In a study that followed 1,061 people with kidney disease for about five years, those whose blood pressure dropped by less than 10% at night were 30% more likely to lose half their kidney function or need dialysis or a transplant.
Short sleep also shows up in the numbers. In an observational study of more than 4,000 women followed for 11 years, those who slept 5 hours or less a night had 79% higher odds of rapid kidney function loss (a drop of 30% or more in eGFR) than those who slept 7 to 8 hours, and even 6 hours was linked with 31% higher odds. A practical approach is to go to bed and get up at the same time every day, even on weekends, and to leave enough time in bed for 7 to 8 hours. If you have persistent sleep trouble, loud snoring or daytime sleepiness, mention it to your doctor.
Two Kidney Numbers To Track
Two tests show whether the habits are working. Your eGFR is a blood test that estimates how well your kidneys filter: 90 or higher is normal, and under 60 for three months or longer indicates kidney disease. Your urine albumin-to-creatinine ratio (UACR) measures how much albumin leaks through the filters, and under 30 mg per gram is normal. Consider getting both checked and then repeating them in about three months. Since the protein leak dropped within two weeks in the salt trial, UACR is the number most likely to move first.
A sensible plan is to start this week with salt and sweet drinks and add one more habit each week after that, while keeping your regular medicines and follow-up appointments.
h2>Frequently Asked QuestionsCan cutting salt really improve kidney function in two weeks?
In one small trial of 20 people with stage 3 to 4 kidney disease, two weeks of low sodium halved the protein leaking into the urine and lowered blood pressure. It did not show a change in eGFR, so it is better described as taking pressure off the filters than as improving kidney function.
Should I drink extra water for my kidneys?
In a one-year trial of 631 people with stage 3 kidney disease, coaching people to drink about two and a half extra cups a day did not slow kidney function loss. Drinking enough to keep urine pale yellow is a reasonable goal. People with kidney stones are the exception, and anyone with a fluid limit should keep to it.
Is plant protein safe if I have kidney disease?
Plant-focused eating was linked with lower kidney strain and a lower risk of kidney disease in the studies cited. But plant foods can be high in potassium or phosphorus, so people with kidney disease should ask their care team or a kidney dietitian which foods fit their lab numbers.
Which tests show whether these habits are working?
Your eGFR (blood test; 90 or higher is normal, under 60 for three months or longer indicates kidney disease) and your urine albumin-to-creatinine ratio, or UACR (under 30 mg/g is normal). UACR is the number most likely to move first. Consider checking both now and again in about three months.
Five-Habit Kidney Checklist
- ☐ Aim for under 2,000 mg of sodium a day if you have kidney disease (ask your care team)
- ☐ Check labels: 5% DV or less is low sodium, 20% or more is high
- ☐ Swap sweet drinks for water, sparkling water, unsweetened tea or black coffee
- ☐ Build meals around beans, lentils, tofu, tempeh, edamame and nuts
- ☐ Walk about 10 minutes after each meal
- ☐ Keep a regular bedtime and aim for 7 to 8 hours of sleep
- ☐ Drink enough to keep urine pale yellow, unless you have a fluid limit
- ☐ Ask for eGFR and UACR tests now and again in about 3 months
This article is for general educational purposes and is not medical advice. Several findings come from small or observational studies, which show associations and cannot prove cause and effect. Never start, stop or change the dose of a prescription medicine without consulting your doctor. If you have kidney disease, coordinate changes to salt, potassium, phosphorus, protein and fluids with your care team.