Sport and Diabetic Nephropathy

Physical activity has always been one of the pillars of diabetes therapy. This is not only because of its beneficial effects on lowering blood pressure and improving the blood lipid profile, but also because of its action of promoting a general sense of well-being.

Sport and physical activity are fun, they demand strength and endurance and thereby increase your self-confidence. In addition, people who are overweight find it easier to lose weight when they undertake regular exercise. People with diabetic nephropathy usually have hypertension as well as diabetes.

Physical activity causes a rise in blood pressure in everyone, which is steeper when hypertension is already present. This obviously depends on the type of exercise. It is well known that blood pressure rises much more during strength and speed training, such as lifting weights or a short fast run, than during endurance training, such as cycling, jogging or swimming.

Sports that lead to short-term high stress are not suitable for people with hypertension because of this peaking in blood pressure, and should be avoided. On the other hand, endurance training, also known as cardiovascular training, has long-term beneficial effects on blood pressure.

After several weeks of regular training the resting blood pressure falls by about 5–10 mmHg; the rise in blood pressure under stress also becomes much smaller. The following show some good types of exercise for people with diabetic nephropathy and some that are not recommended.

Rules for Exercising

The resting blood pressure should be less than 140/90 mmHg. Because the increase that will occur during an exercise program cannot be predicted, it is best to undergo an ergometric examination by a doctor beforehand. This might be walking on a treadmill or cycling on an exercise bike.

This enables the doctor to measure the rise in your blood pressure and your pulse rate under controlled conditions. For healthy men and women, the upper limit for the normal rise in blood pressure under stress is 200/100 mmHg. If the blood pressure rises above 250/120 mmHg, the exercise should be stopped.

For patients with nephropathy, there is at present no ‘official’ guideline for the rise in blood pressure under stress. This must be considered individually. For example, if someone has only microalbuminuria and no further heart or circulatory complications, they should be able to follow the values given for healthy people.

If, however, macroalbuminuria is present and the person is also known to have retinopathy or coronary artery disease, such peak blood pressure values are certainly too high. Before starting a training program, it is best to get your blood pressure under better control and to start exercising very carefully.

After all, it is no problem today to measure your blood pressure yourself at any time and any place – so why not when exercising? Another frequently used method to guide the intensity of your training is to measure your pulse rate.

The calculated pulse rate should be reached during endurance training but not exceeded. Something to watch is that beta blockers and some calcium antagonists that are used to treat hypertension can slow the pulse rate. The optimal pulse rate during exercise should then be about 15–20% lower than as calculated above.

Typical Problems

When the kidneys stop working properly, the body can no longer clear itself of toxins and excess water. The typical symptoms of kidney failure then appear – earlier in some people, later in others:

  • As water excretion falls, so does the volume of the urine. Water is retained in the body in a condition known as edema. This usually occurs first in the ankles: they swell and it is easy to make a ‘thumbprint’ in them. Later the whole leg may become swollen. If there is also water retention in the lungs, breathlessness occurs and this is a warning sign of renal failure.
  • The skin is pale, because the density of the red blood cells falls. This is because the kidneys can no longer make enough erythropoietin, a hormone that is needed to make red blood cells in the bone marrow.
  • The calcium profile may rise: in some people this leads to cramps and muscle weakness in the legs. A very high calcium profile can cause life-threatening disturbances to the heart rhythm (cardiac arrhythmias); it should therefore be monitored regularly.
  • One consequence of kidney failure is that the concentrations of calcium and phosphorus in the blood change. This can lead to changes in the bones, known as renal osteopathy. These develop because the kidneys are an important source of vitamin D, which is needed to help absorb calcium from the food in sufficient quantities and to strengthen bone.

In addition, the low calcium concentration in the blood stimulates the body to produce more parathyroid hormone, which pulls calcium out of the bones and thereby contributes further to skeletal weakening.

  • Phosphorus metabolism is also disturbed. Phosphorus is found in the bones and, like calcium, is an important component of enzymes and cellular proteins. It is taken up in food and excreted via the kidneys. When kidney function is impaired, the amount of phosphorus in the blood rises.

This high phosphate profile lowers the calcium profile and thereby triggers an automatic increase in the release of parathyroid hormone, which controls phosphorus excretion via the kidneys. But this induces more calcium to be resorbed from bone, which over time leads to softening of the bones.

This can manifest itself as bone pain and spontaneous breaks. These changes in mineral content are responsible for a variety of other symptoms in people with kidney failure, including itching, chalky deposits in the joints and muscle weakness.

  • The rising concentrations of urea and toxins, which are no longer excreted properly, result in frequent tiredness followed by apathy. You experience disturbed sleep and loss of concentration, you lose your appetite and may suffer from nausea and vomiting. Women experience problems with menstruation, often missing periods completely. In men, a possible consequence is impotence.
  • The toxins in the body may give rise to nerve damage, leading to burning sensations in the soles of the feet, pain in the legs, particularly at night, or muscle weakness. The technical term for this is ‘uraemic polyneuropathy’.

What you can do about these problems

The amount of urea in the blood can be reduced by eating less protein. The water content of the body can be reduced by cutting your salt intake. These dietary modifications are particularly important at the stage of terminal renal insufficiency. In addition, you should take care not to consume too much phosphorus in your diet.

This is not easy, because phosphorus is present in almost all foodstuffs. Foods particularly rich in phosphorus are those comprising mainly protein, such as meat, milk and dairy products, as well as nuts, especially almonds, and ready-made meals. Dietary measures are usually not enough to normalize the phosphorus concentration in the blood.

Drugs known as phosphate binders have to be taken with meals. These bind to phosphate in the food and prevent it being absorbed by the body; instead it is excreted in the faeces. So that the calcium profile does not rise too high, you should not eat too much calcium in your diet.

Calcium-rich foods include vegetable and fruit juices, dried fruits, nuts, mushrooms and precooked potato products. Although these recommendations may sound complicated at first, in practice it is not that difficult to follow them. If you combine different foodstuffs, it is still possible to prepare varied and tasty meals.

There are plenty of special cookbooks that can help and you could also obtain special education about nutrition. The lack of red blood cells, known as anemia, is today easily treated by administration of artificially produced erythropoietin. The water retention can be combated with diuretics, which stimulate urination.

By these methods, the complaints caused by terminal renal insufficiency can be at least partially improved. All the same, the appearance of these symptoms is clear evidence that the kidneys can no longer perform their allotted functions themselves but need help – kidney replacement therapy.

It is understandable that many people try to postpone starting dialysis for as long as possible, but that does not do any good. Although there are no general guidelines for the exact time at which to start replacement therapy, it should not be delayed for too long.

Personal well-being and the success of the dialysis treatment are both better when the patient has not lost too much weight by waiting too long and become totally discouraged by the unpleasant symptoms of kidney failure.