Research Review: High-protein diets – safe for kidneys

High protein diets (HPDs) have been promoted as safe for the kidneys. Many articles have been published on this topic, which have relied on conflicting results from animal studies. This article reviews the literature on HPDs, present evidence on their safety in humans, and point out limitations in current HPD research.

A lot of people are very over-weight, and a lot of doctors are very worried about this issue. The main reason is that they do not know how to manage the situation, and they are not taking the right measures. The first step is to maintain their body weight; however, since they are over-weight, they must not lose their extra pounds. If you are obese, you should consider losing weight as soon as possible. For this, you may be interested in a high protein diet. In a high protein diet, you consume four to five times the amount of protein you consume in a normal diet.

Protein is essential to a healthy diet. It is a building block of muscles and supports healthy hair and nails, but too much protein can overload the kidneys, causing them to work overtime and do damage to the body. High-protein diets are now known to be linked to increased kidney injury, and some experts have suggested that protein should be limited, especially for people with kidney issues. The good news is that there is a safe and effective way to eat more protein without risking kidney problems.

When I tell people how much protein I eat, the first thing they say is, “That’s bad for your kidneys.”

Are all of these people medical professionals? Nephrologists? Psychics, perhaps, who communicate with my kidneys on the other side of the veil?

No, but the ordinary individual intuitively understands that taking 35 percent of one’s calories from protein is hazardous for the kidneys. You’ll end up on dialysis or feeling like you’ve slept with a cinder block under your lumbar spine if you eat too many chicken breasts.

When you ask these people what protein does to the kidneys, you’ll get a lot of ambiguity. It’s just a disaster.

Meanwhile, my workplace colleague, a cola-guzzling, fry-eating, immovable object, is left unchecked regarding their lifestyle choices.

Kidney health

Is it true, however, that protein can hurt my kidneys?

Before I go over this notion in detail, let’s go over what kidneys perform and how your doctor can tell if your kidneys are healthy and working.

Kidneys perform a variety of functions. They:

Filtering your blood and removing waste
control the amount of water and different salts in your blood
aid in the maintenance of a healthy blood pH (how acidic or alkaline your blood is)
manufacture erythropoietin and other hormones (among others)

The potentially increased load of having to process protein is the basis for the notion that protein harms kidneys – assuming anyone can ever prove it. More protein, the theory goes, means more filtration challenges for the kidneys, which leads to a kidney explosion or renal labor strike.

Kidney function testing

There are around a half-dozen kidney function tests, but they all assess the amount of fluid (blood plasma) your kidney filters at any one time.

Rate of glomerular filtration (GFR)

The glomerular filtration rate is the rate of filtering (GFR). GFR stands for glomerulus filtration, which occurs in a specific area of the kidneys where blood plasma is filtered.
GFR is difficult to assess since you must be administered with a material that passes through the glomerulus without causing any problems. In most cases, a chemical known as inulin is employed (not be confused with insulin).
Following that, GFR is computed using blood and urine samples. The rate at which inulin leaves the circulation and enters the urine determines GFR.
GFR is typically 90-120 mL/min. Kidney failure is defined as a urine output of less than 15 milliliters per minute.

Clearance of creatinine

Because of the breakdown of creatine phosphate in muscle, creatinine is a natural consequence of physical exertion. More muscle mass means more creatinine is absorbed into the bloodstream.
GFR is measured indirectly using creatinine clearance (filtration). Because the body produces creatinine at a fairly constant pace, with only a little amount being reabsorbed, the rate at which creatinine appears in your urine is the rate at which your kidneys can filter it.
Men should have a flow rate of 97-138 mL/min, while women should have a flow rate of 88-128 mL/min.

Indirect techniques of determining kidney function include: Albumin in the urine, BUN in the blood, and plasma creatinine

Instead of attempting to measure filtration rate, look for increases in plasma levels of substances that your kidneys are designed to eliminate, such as creatinine and urea.
Higher levels of plasma creatinine or blood urea (Blood Urea Nitrogen; BUN) indicate that your kidneys aren’t filtering the surplus effectively enough.
For women, normal creatinine levels are 0.5 to 1.0 mg/dL (45-90 mol/L) and for men, 0.7 to 1.2 mg/dL (60-110 mol/L). These figures will rise as muscle mass increases. BUN levels of 10-20 mg/dL are considered normal.
Urine albumin is a test that determines how much albumin is present in your urine. There ought to be none. If there is any, it indicates that the kidneys have been damaged, enabling albumin to slip through.
Normal kidney function is defined as less than 20 g of albumin per minute.

As a result, we can utilize these types of tests to assess if the kidneys are functioning appropriately. This week’s study includes renal testing and other tests to see if a high-protein diet is safe and useful in a group that is already at risk of kidney impairment.

High protein levels and renal function are both tested.

Now that we know how to evaluate kidney function and potential damage, we can utilize these assays to see if high-protein diets indeed injure the kidneys.

We could examine renal function and high-protein diets in healthy persons to figure this out. We may even take it a step further and test a high-protein diet on those who already have reduced kidney function, such as obese diabetics.

Obesity, diabetes, and renal disease are all linked.

Obesity and type 2 diabetes can both cause and aggravate renal disease (1). End-stage renal disease (ESRD) increased proportionately to body mass index (BMI) in one large-scale investigation, for example: as BMI climbed, so did kidney disease. (2)

Overweight and poor nutrition aggravate cardiorenal damage mechanisms (click to enlarge). Sowers et al., Sowers et al., Sowers et al (1)

Question for investigation

This week’s study looks at how a high-protein diet and resistance training can help persons with type 2 diabetes who are overweight or obese. Their kidneys did not explode, contrary to popular belief.

TP Wycherley, M Noakes, PM Clifton, X Cleanthous, JB Keogh, and GD Brinkworth. In type 2 diabetes patients who are overweight or obese, a high-protein diet combined with resistance exercise training promotes weight loss and body composition. May 2010;33(5):969-76 in Diabetes Care. 11 February 2010, epub.

Methods

There were males and women among the participants, with an average age of:

35.4 kg/m2 BMI (roughly 39 percent body fat)
55 years of age
103 kg (40 kilograms fat + 63 kilograms lean body mass)

There were four groups in this study:

Members of the control (CON) group were put on a low-calorie diet (53 percent carbs, 19 percent protein and 26 percent fat)
Members of the high-protein (HP) group ate a low-calorie, high-protein diet (43 percent carbs, 33 percent protein and 22 percent fat)
Members of the control Plus resistance training (CON+RT) group ate a low-calorie diet and worked out with weights three times a week.
Members of the high-protein + resistance training (HP + RT) group ate the same hypercaloric high-protein diet as group #2, but they also did resistance training like group #3.

The experiment lasted 16 weeks. Before and after measurements of body weight, body fat, blood pressure, strength, and blood tests were taken.

Diet

In the literature, different definitions of “high protein” have been proposed. Bodybuilders and strength trainers often consume 2.2-4.4g of protein per kilogram of body weight each day (1-2g/lb/day).

High protein was defined as 33 percent of total calories, or roughly 1.2 grams per kilogram per day (0.55 grams per pound per day) in this study. This group ingested around 2.04 grams of protein per kilogram of lean body mass (or 0.92 grams per pound of lean body mass).

While this amount is higher than what standard food guidelines recommend, I wouldn’t call this a high protein diet based on what bodybuilders and strength athletes often consume.

Training

Groups 3 and 4 did resistance training three times a week, with at least one day off in between.

Each workout consisted of eight exercises performed at 70-85% of one repetition maximum for 8-12 repetitions for two sets, with 1-2 minutes of rest in between. If they could complete more than 12 reps for both sets, the weight was raised.

The following were the exercises:

leg press ups
extension of the knees
push your chest
shoulder flexion
pullups on the lats
row of seated people
triceps extension
sit-ups

Except for the sit-ups, all of the activities were performed on machines.

Overall, it’s not a really amazing training routine, but progressing from nothing to something can enhance strength and muscle mass.

Results

Fat loss is achieved by combining a high protein diet with resistance training.

All groups lost weight (see Figure 1 & 2).

The HP+RT, on the other hand, dropped the most weight and fat (13.8 kg and 11.4 kg, respectively).

In addition, the HP+RT group dropped more fat around their waist, losing 11.4 cm compared to the other groups, which lost 8.2cm (CON), 8.9cm (HP), and 11.3cm (CON+RT).

Resistance training and a high protein diet equals a stronger body.

Both groups that worked out (CON+RT & HP+RT) got stronger while the other groups (CON & HP) got weaker when you look at their 1 RM on bench press (Figure 3).

Measurements of blood

All groups had improvements in their blood pressure after the 16 weeks (15 mmHg decrease in systolic blood pressure & 8 mm Hg decrease in diastolic blood pressure).

There were considerable improvements in all of the following areas for all of the groups:

1.9 to 2.7 mmol/l plasma glucose
Insulin levels in the blood (3.5–7.9 mU/l)
(0.3 to 0.6 mmol/l) triglycerides
cholesterol total (0.6 to 0.8 mmol/l)
LDL cholesterol (0.2 to 0.5 mmol/l) is a kind of cholesterol that is found in the blood.

In terms of blood measurements, there were no differences between groups, while the authors indicate that having more persons in the trial (greater statistical power) would have helped show some blood differences. They reasoned that because the HP+RT group had marginal blood improvements across the board, more persons in the research would show higher blood measure gains. But until they conduct a larger study with more people, we can only speculate.

The HDL cholesterol was unusual in that it decreased somewhat (0.1 mmol/l) in all groups except the CON over the 16 weeks.

Legend

Hypocaloric diet is a disadvantage (19 percent protein)
HP refers to a low-calorie, high-protein diet.
CON+RT – Constraint diet plus resistance training
HP+RT Is a high-protein, low-carbohydrate diet combined with resistance training.

Figure 1: After 16 weeks of testing, the body weight was reduced.

Figure 2: After 16 weeks of testing, body fat was reduced.

Figure 3: After 16 weeks of testing, the change in bench press strength as determined by 1 repetition maximum is shown.

No kidney troubles if you eat a lot of protein.

Here’s some information to assist you avoid the Protein will cause your kidneys to explode crowd.

You’d expect that since diabetes is the leading cause of kidney failure and obesity is a risk factor, these overweight and obese diabetics eating high protein diets would show indications of renal dysfunction. Nope.

The researchers found no difference in renal function between the high protein diet and the control diet when they measured creatinine clearance and urine albumin. The rate of creatinine clearance decreased over time, whereas microalbuminuria improved.

Conclusion

When compared to individuals on a calorie-limited diet with 19 percent protein, overweight and obese diabetics (type 2) who eat a high protein (33%) but calorically restricted diet while weight training shed more overall weight and fat, and had a smaller waist circumference.

There were no variations in blood lipids or other blood measurements across groups (albeit the high-protein group would have done better with more participants), but there was an improvement over the 16-week study period.

Despite fears that a high-protein diet may compromise kidney function (particularly in diabetics at high risk of renal failure), no variations in kidney function parameters were found across groups.

In conclusion

Weight training combined with a high protein diet (33% of calories) is more effective for fat loss than weight training alone or weight training combined with a lower protein diet (19 percent ).

The renal function of obese and overweight diabetics on a high protein diet or a control diet for 16 weeks was the same. Even in these people who were at increased risk, adding protein had no harmful consequences.

Everyone, have fun with your protein shakes.

References

To see the information sources mentioned in this article, go here.

James R. Sowers, Adam Whaley-Connell, and Melvin R. Hayden Overweight and obesity play a role in cardiorenal syndrome. 5-12 in Cardiorenal Medicine, vol. 1, no. 1 (2011).
CY Hsu, CE McCulloch, C Iribarren, J Darbinian, AS Go. The relationship between BMI and the risk of end-stage renal disease. 21–28 in Ann Intern Med 144 (2006).
The Physiology Coloring Book, by W. Kapit, R. I. Macey, and E. Meisami. HarperCollins, New York, 1987, pp. 54-58.
R. Freeman Eckert, R. Freeman Eckert, R. Freeman Eckert, R. Freeman Eckert, R. Freeman Eckert, R. Freeman Eckert, R. Freeman Eckert, R. Free
Human Physiology, 3rd edition, Rhoades RA, Pflanzer RG. Saunders College Publishing, Orlando, 1996.
Diabetes-related kidney disease.

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Protein, low carbs, and controlled fat intake are all effective ways to lose weight and keep it off. But what makes a particular diet work? What are the possible side effects and benefits? The following blog post seeks to answer these questions.. Read more about excess protein in the diet has been linked with decreased bone and let us know what you think.

Frequently Asked Questions

What protein foods are bad for kidneys?

The kidneys are a vital organ that filters the blood and removes waste from the body. Protein foods like red meat, eggs, and dairy can cause kidney damage over time if they are consumed too much.

Are high protein vegetable based diets safe for kidney function a review of the literature?

Yes, high protein diets are safe for kidney function.

Is plant based protein safe for kidneys?

Plant based protein is not safe for kidneys.

This article broadly covered the following related topics:

high protein diet and creatinine
effect of high protein diet on gfr
bun creatinine ratio high protein diet
too much protein kidney damage
best protein for kidney disease