For people in any stage of kidney disease, a low-protein diet (.65-1.0 gms
protein/kg body weight) can reduce some of the more unpleasant symptoms of
kidney disease (anorexia, nausea, vomiting, headaches, and general
yukkiness), which is no small thing. Attempting to follow a low-protein
diet will almost automatically reduce the amount of saturated fat and
cholesterol in one's diet, which can contribute to the control of blood
pressure.
2) Regulates the levels of electrolytes in the body. The body needs
potassium, but too much potassium can be fatal. Someone who is in the early
stages of kidney disease can probably handle potassium, but when the kidneys
begin to fail, dietary potassium must be limited. There is some evidence in
animal studies that potassium citrate may inhibit the development of PKD
cysts, although human studies are just getting under way. But, considering
the dangers of excess potassium, anyone considering potassium supplements
should consult with his or her doctor and be carefully monitored.
3) Regulates the level of fluids in the body and removes excess fluid. A
healthy kidney flourishes on lots of water--the more dilute the urine is, the
easier it is for the urine to carry the toxins out of the body. Six to eight
8-0z glasses of fluid a day are recommended. Dehydration makes the kidney
work harder. As the kidney deteriorates, the buildup of fluid in the body
may make the heart work harder, leading to heart damage, and definitely makes
the person uncomfortable. At this point, the doctor may introduce diuretics,
which force fluid out of the body or, eventually, dialysis may be needed.
People on dialysis often have to limit their fluid intake.
Caffeine and alcohol are diuretics, so they can cause the body to become
dehydrated and force the kidneys to work harder. Anyone with a caffeine
habit would therefore benefit by cutting back, and by drinking and additional
half cup of water above the 6-8 glasses recommended for everyone for each
cup of caffeinated beverage. Alcohol should be balanced by an additional
glass for every glass of alcohol.
4) Regulates blood pressure through the release of renin. Not only can
deteriorating kidneys cause the blood pressure to rise, but high blood
pressure, from any cause, can damage the kidneys. So keeping the blood
pressure at normal, or even low-normal levels, is essential. Diet can
contribute to maintaining blood pressure through weight loss. Exercise also
helps. But medication may still be necessary.
In some people, high blood pressure is made worse by excess sodium, so
doctors often advise people at risk for high blood pressure to watch their
sodium intake. Sodium also promotes the retention of fluids, so someone with
a fluid retention problem may be advised to limit sodium.
5) Converts dietary and sunshine vitamin D into a form usable by the body.
Activated vitamin D is essential to maintaining calcium in the bone. The
amount of vitamin D required by a healthy kidney is small, and almost always
provided by the diet or short exposures to the sun (1/2 hour 3 x week).
Supplements are rarely necessary. Since dietary and sunshine vitamin D alone
cannot help an ailing kidney, taking more probably won't help much. When the
kidneys stop converting vitamin D, a prescription form of vitamin D
(Rocaltrol) should be taken.
6) Maintains a balance between calcium and phosphorus, which is also
necessary to bone health. A disruption in the calcium/phosophorus balance is
an effect of kidney disease which only shows up years later in fragile bones
and frequent fractures. It is therefore important that bone density and
serum calcium and phosphorus be monitored during the entire course of kidney
disease. It is a lot easier to prevent osteoporosis than it is to treat it.
Limitation of dietary phosphorus, however, need not be an automatic part of a
pre-dialysis diet and excess calcium can contribute to kidney stones and
calcification of the joints.
High phosphorus levels are also implicated in the itching which is the bane
of many kidney patients. Although this is usually a problem only for people
with very little kidney function left, it is a question itchy people with low
creatinine need to raise with their doctors.
7) Secretes erithropoetin, which is necessary for the production of red blood
cells. Many people think that anemia is caused by low iron levels, and can
be treated with high-iron foods or iron supplements. However, the anemia of
kidney disease is caused by erithropoetin deficiency. It is treated by
injections of recombinant erithropoetin (Epogen/Procrit). Epogen requires
iron to work, so people taking Epogen may need iron supplements also.
However, since excess iron in the body can be harmful, one should not take
iron supplements unless specifically instructed by a physician.
In addition to these issues, which are common to all people with kidney
disease, people with PKD have a somewhat higher than average tendency to form
kidney stones. Still, only about 20% of PKDers have problems with kidney
stones. A diet or medications which raise the alkalinity of the urine may be
advisable for those people who are likely to form stones. However, since an
alkaline urine can promote kidney infections, it should be undertaken only
after discussing all the advantages and disadvantages with one's physician.
In general, one is fairly safe following the American Heart Association diet,
which advocates less than 30% fat, 10-20% protein (stay closer to the 10%
protein) and 50-60% complex carbohydrates. When one is getting close to
dialysis, one should consult with a renal dietician. For people on dialysis,
the diet is an important part of their treatment plan, and each diet needs to
be tailored to the needs of the individual.
A word of warning: There are many cookbooks available for a "renal diet."
Usually it means a diet for people on dialysis--low in potassium, sodium, and
phosphorus, medium to high in protein. For people who are not yet on
dialysis, this diet can be at best unnecessarily restrictive and at worst,
dangerous. Talk to your renal dietician.
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