By Dr. Mercola
Your kidneys — two bean-shaped organs — are located just below your rib cage one on either side of your spine. Positioned on top of each kidney are your adrenal glands. Each day, your kidneys filter up to 150 quarts of blood and flush out waste products through your urine.
One of the reasons why you need to drink enough water is to ensure healthy kidney function. In fact, chronic low-grade dehydration is one of the most common causes of kidney stones.
Poor kidney function is also associated with a number of other serious health problems, including diabetes, hypertension, and heart disease. Common signs of kidney problems include:
- Frequent urination
- Problems urinating
- Pain or burning sensation during urination
- Constant thirst
Good kidney function1 is essential for maintaining homeostasis in your body, starting with the composition of your blood. For example, your kidneys are responsible for maintaining proper pH level and electrolyte balance (the ratios of sodium, potassium and phosphates).
They also produce hormones that make red blood cells, and those that help regulate your blood pressure.
Dietary Factors That Threaten Kidney Health
Waste products removed by your kidneys and eliminated through your urine include urea and uric acid, produced from the breakdown of proteins and nucleic acids respectively.
Excessive protein intake increases urea, while uric acid is a byproduct of both protein and fructose metabolism. Fructose typically increases uric acid within minutes of ingestion.
I became fully aware of the dramatic and devastating impact fructose has on your uric acid levels when I interviewed Dr. Richard Johnson on this topic.
Most Americans consume three to five times more protein than they need, and two to four times (or more) fructose than is considered safe. These two dietary factors, alone and especially in combination, places significant stress on your kidneys and promote kidney disease and kidney stones.
Kidney stones are particularly linked to a diet high in processed fructose and other sugars, as sugar upsets the mineral relationships in your body by interfering with calcium and magnesium absorption. The phosphorus acid in soda also acidifies your urine, which promotes stone formation.
Analgesic drugs are also known to damage your kidneys when taken in excess, and/or over long periods of time. This includes aspirin, anti-inflammatory drugs (NSAIDs), ibuprofen, naproxen, and acetaminophen — especially when taken in combination with alcohol, even if the amount of alcohol is small.
Research2,3 shows that combining alcohol with acetaminophen raises your risk of kidney damage by 123 percent, compared to taking either of them individually. Long term alcohol consumption and smoking also take their toll on kidney function.
3 Dietary Keys to Protect Kidney Function
To protect your kidney function, keep the following three basic factors in mind:
- Restrict protein to just what your body needs. An ideal protein intake is likely around one-half gram of protein per pound of lean body mass, which for most is 40 to 70 grams a day.
The American Kidney Fund recommends restricting protein to a maximum of 50 grams if you have kidney disease4
- Restrict fructose to 25 grams per day (about 6 teaspoons), or less (especially if you’re insulin/leptin resistant)
- Drink pure, clean water. Simply swapping out sweetened beverages like sodas and fruit juices for pure water can go a long way toward improving your kidney function and overall health.
The best way to gauge your water needs is to observe the color of your urine (it should be light pale yellow) and the frequency of your bathroom visits (ideally, this is around seven to eight times per day).
How to Calculate Your Protein Requirement
Considering the fact that the majority of Americans are overweight or obese, I recommend calculating your individual protein requirement based on lean bodyweight (your total weight minus your fat) only.
For optimal health, I believe most adults need about 1 gram of protein per kilogram of lean body mass (not total body weight), or 0.5 gram of protein per pound of lean body mass.
In this formula, you must first determine your lean body mass. To do that, subtract your percent body fat from 100. For example, if you have 30 percent body fat, then you have 70 percent lean body mass.
Then multiply that percentage (in this case, 0.7) by your current weight to get your lean body mass in pounds or kilos. As an example, if you weigh 170 pounds; 0.7 multiplied by 170 equals 119 pounds of lean body mass.
Using the “0.5 gram of protein” rule, you would need 59.5 or just under 60 grams of protein per day.
100 – % of body fat = % of lean mass X actual weight X 0.5 gm protein = total grams of protein recommended
Example: A 170 lb individual with 30% fat mass
100% total weight – 30% fat mass = 70 % lean mass
0.70 X 170 = 119 X 0.5 = 60 grams of protein recommended
Translating Ideal Protein Requirements Into Foods
To determine whether you’re getting too much protein, simply calculate your lean body mass as described above, then write down everything you’re eating for a few days, and calculate the amount of daily protein from all sources.
Again, you’re aiming for one-half gram of protein per pound of lean body mass, which would place most people in the range of 40 to 70 grams of protein per day. If you’re currently averaging a lot more than that, adjust downward accordingly.
The chart below can give you a general idea of the protein content of many foods. I personally use Cronometer.com to enter everything I eat and carefully calculate my protein requirement to the gram.
Just be sure to enter the correct foods and amounts into the program, as the results will be inaccurate if you don’t enter the correct details.
| Red meat, pork, and poultry average 6 to 9 grams of protein per ounce. |
An ideal amount for most people would be a 3-ounce serving of meat (not 9 or 12 ounce steaks!), which will provide about 18 to 27 grams of protein
|Eggs contain about 6 to 8 grams of protein per egg.
So an omelet made from two eggs would give you about 12 to 16 grams of protein.
If you add cheese, you need to calculate that protein in as well (check the label of your cheese)
|Seeds and nuts contain on average 4 to 8 grams of protein per quarter cup
||Cooked beans average about 7 to 8 grams per half cup
|Cooked grains average about 5 to 7 grams per cup
||Most vegetables contain about 1 to 2 grams of protein per ounce
Interestingly, while fish is typically considered a good source of protein, most fish contain only HALF of the protein found in beef and chicken. The reduced protein content in fish may actually be one reason why the Mediterranean diet is linked to life extension and reduced risk for chronic disease.5 In essence, those who eat more fish than red meat are automatically getting far less protein.
Other Dietary Dos and Don’ts If You Have Kidney Disease and/or Stones
If you have kidney disease, you also need to reduce consumption of foods rich in phosphorous, as they may promote the formation of kidney stones. On the other hand, if you have problems urinating but don’t yet have kidney disease, try adding more potassium-rich foods (primarily vegetables and seeds) to your diet. Depending on the type of kidney stone you have, you may also need to modify your diet in other ways:
- Struvite stones: Found more often in women, these are almost always the result of urinary tract infections
- Cystine stones: Represent a very small percentage of kidney stones. These are the result of a hereditary disorder that causes your kidneys to excrete massive amounts of certain amino acids (cystinuria)
- Uric acid stones: These are a byproduct of protein and fructose metabolism, and are commonly seen with gout. Cutting your protein and fructose consumption is essential for preventing and treating these types of stones. Taking potassium citrate (which lowers urine acidity and reduces urine excretion of calcium) may also help prevent uric acid stones6
- Calcium oxalate stones:7 These are the most common. About 80 percent of kidney stones are calcium based, and about 80 percent of those are calcium oxalate stones. Typically, they are the result of insufficient water intake and dietary factors, including excessive oxalate, protein, and processed salt consumption
Oxalate is found in some fruits and vegetables, but your liver produces most of your oxalate. If you are found to have oxalate stones, your physician may recommend avoiding oxalate-rich foods. Also, make sure you’re getting enough magnesium, as magnesium helps prevent calcium from combining with oxalate to form stones8
If you have calcium oxalate stones, rather than reducing your calcium intake you’ll want to minimize the amount of oxalates in your body. Soy and beer are two primary culprits that should be avoided. For reasons that are unclear, grapefruit juice has been shown to increase the risk of kidney stones9 and is therefore best avoided. Other foods that contain high levels of oxalate10 that you’ll want to avoid if you have calcium oxalate kidney stones include:
| Spinach || Rhubarb|| Chocolate
| Parsley|| Beetroot|| Most legumes,11 including green beans
| Wheat and other grain-based flours12|| Pepper|| Nuts13
Potassium and Kidney Health
Potassium is a nutrient that receives a great deal of attention when you have kidney disease. On the one hand, potassium (a mineral and electrolyte) is essential for your cells, tissues, and organs to function properly. It plays a vital role in heart health, digestive, and muscular function, bone health, and more.
While potassium is found in many foods commonly consumed in the U.S. — including fruits, vegetables, dairy products, salmon, sardines, and nuts — only 2 percent of U.S. adults get the recommended daily amount of 4,700 milligrams (mg).
This can be problematic because potassium needs to be kept in proper balance with sodium in your blood. If you consume too much sodium, which is common if you eat many processed foods, you’ll have an increased need for potassium. Others who are at particular risk of low potassium (hypokalemia) are those with chronic malabsorption syndromes, such as Crohn’s disease, or those taking heart medicine (particularly loop diuretics).
However, anyone who eats a poor diet — an excess of processed foods and not enough fresh, whole foods — is potentially at risk of inadequate potassium levels.
All of that said, if you have severe kidney impairment, you typically need to restrict your intake of high-potassium foods.14 Why? Because your kidneys are responsible for maintaining the proper amount of potassium in your body, and when they’re not working well, your levels could become excessively elevated.
Potassium helps maintain a regular heart rhythm and plays a role in muscle function, and when your potassium level gets too high, it can lead to irregular heartbeat and/or a heart attack.
Recommended Potassium Intake Varies Depending on the Health of Your Kidneys
If your kidneys are working well, the recommended amount of potassium is about 4,700 mg per day,15 which also needs to be balanced with sodium. As a general rule, your potassium to sodium ratio should be around 5:1. The easiest way to achieve this ratio is to eat REAL food (lots of fresh vegetables), ideally organically and locally grown to ensure optimal nutrient content.
This type of whole food diet will naturally provide much larger amounts of potassium in relation to sodium, whereas a processed food diet is virtually guaranteed to provide you with an upside-down ratio. Juicing your vegetables is a good way to ensure you’re getting enough potassium.
If you have kidney disease, you need to pay careful attention to your potassium level and dietary intake. Most who are being treated for kidney disease will monitor their potassium level by measuring it monthly, and potassium-restricted diets typically recommend keeping potassium intake to about 2,000 mg per day.
Besides monitoring your protein and sugar/fructose intake and drinking plenty of water, adding the following foods to your diet can also help promote optimal kidney function.16,17,18,19,20
|Red bell peppers: low in potassium, rich in vitamins A, B6, C, folic acid and fiber
||Cherries: rich in antioxidants and phytochemicals
|Cabbage: low in potassium, rich in vitamins C and K, and fiber, and phytochemicals that protect against free radical damage
||Red and purple grapes: rich in antioxidants; the skin is particularly rich in resveratrol
|Cauliflower: high in vitamin C, folate and fiber
||Watermelon: rich in water, with diuretic properties, allowing you to produce more urine to flush out toxins
|Garlic: antioxidant, anti-inflammatory, and anti-clotting properties
||Lemon juice: helps reduce kidney stone formation
|Onion: low in potassium, rich in antioxidants, particularly quercetin, which has natural antihistamine properties
||Pumpkin seeds: rich in antioxidants, vitamins and minerals, especially magnesium, which helps reduce the risk of kidney stones
|Apples: high in fiber, antioxidants, and anti-inflammatory compounds. Raw organic apple cider vinegar is helpful for the prevention of kidney stones
||Kale: lower in potassium, good source of vitamins A and C, rich in iron — the latter of which is important for kidney health. Many with kidney disease are also iron deficient21
|Berries,22 including blueberries, raspberries, and strawberries
||Sweet potatoes: rich in beta-carotene, vitamins A and C, and fiber, and a good source of B6 and potassium
Herbal Kidney Cleansers
A number of herbs also have kidney-cleansing properties, including the following:
|Ginger: purifies the blood and kidneys of toxins
||Red clover: diuretic that stimulates waste removal from the kidneys
|Turmeric: has antiseptic and anti-inflammatory properties that help prevent and treat kidney infections and inflammation ||Chanca Piedra: Used in South America to break up kidney stones (its Spanish name actually means “stone breaker”)
|Dandelion: a natural diuretic that helps strengthen the kidneys and soothe urinary tract problems ||Hydrangea root: Native American remedy for kidney stones
|Nettle: natural diuretic that helps purify blood and treat urinary tract infections; also high in iron, making it beneficial for building blood ||Uva ursi root: helps treat urinary and bladder problems
|Marshmallow root: natural diuretic that helps treat urinary tract infections, kidney stones, and bladder infections ||Gravel root (Joe-Pye weed): Indian remedy for urinary tract and kidney health
|Juniper: improves kidney function and helps treat urinary tract infections and kidney and/or bladder stones.
Avoid juniper berry if you have a kidney infection and/or are pregnant. Also don’t take continuously for more than four weeks
|Goldenrod root: Native American remedy traditionally used to support urinary tract and kidney health
|Yarrow root: a natural diuretic with antiseptic and anti-inflammatory properties; helpful for urinary tract infections