EXERCISE AND DIET

High blood pressure is a major risk factor for cardiovascular disease. With renal involvement, this risk is increased 3 to 5-fold.

Hypertension, and therefore cardiovascular disease risk, can be largely prevented by following a diet low in:

• saturated fats and cholesterol (chicken skin, visible fat on meat, full fat dairy products, palm kernel oil, coconut, butter and hard margarine. Eggs should be limited to 2 – 3 per week, and not all at the same time)
• salt (tinned, canned and processed foods, spices containing sodium, biltong, salty biscuits, stock cubes, packet soups, health, onion or garlic salt, pre-prepared meals, take-aways, meat and vegetable extracts, food flavourings containing MSG).

A diet high in fibre (oats, fruits and vegetables, as well as whole grain products) is also important in lowering cholesterol levels.

Cessation of smoking, weight loss and physical activity also play an important role in managing cardiovascular disease and associated renal complications.

Calcium oxalate stones are found in 80 per cent of patients, and are largely preventable by diet. The cornerstone of this diet is avoidance of oxalate containing foods, namely rhubarb, strawberries, nuts, regular tea, wheat bran (digestive bran etc.), spinach, chocolate, beetroot and Swiss chard. The following must also be consumed in limited quantities (i.e. ~ once a month): Celery, green beans, beans in tomato sauce, collards, okra, tomato juice/puree/paste, lemon peel, cocoa powder, tomato/vegetable soup, chocolate-type drinks, brinjal, leeks, red currants, cranberry juice and berries (black, blue, goose, raspberries etc.)

Adequate calcium intake is also important; thus milk, cheese and yogurt should be eaten daily.

Fluid intake of 2 litres of water daily is vital to ensure an adequate urine volume and thus a decreased risk of stone formation.

This implies that protein is being lost in the urine. Adequate but not excessive protein intake at between 0, 8 – 1 g / kg is recommended as a protein intake. Exceeding this leads to further protein losses in the urine and further damage to the kidneys. This translates to a 90 g protein portion for a person weighing 90kg (e.g. meat the size of the palm of hand).

Patients with diabetes should be following a diet that excludes sugar and all sugar containing products. When the kidneys are involved, this becomes even more important as high levels of sugar in the blood (blood glucose) can result in further damage to the kidneys and other organs (heart, lungs etc.). Contrary to normal diabetic guidelines where whole wheat and whole grain foods are recommended, these patients should be eating rye, brown or white bread. Cereals allowed would include oats, sorghum and mealie meal. The reasoning behind this is that whole grain products contain phosphate which is one of the first “waste products” to be retained by the body when the kidneys are impaired. When phosphate levels become too high, calcium is taken out of the bones and teeth leading to weak and brittle bones and thus an increased risk for some osteo disorders. Furthermore, calcium and phosphate form small crystals which can then be deposited on the kidneys, heart, lungs, liver and skin leading to organ damage. Foods that are high in phosphates and should therefore be taken in limited amounts, if at all, include: chocolate containing drinks, nuts and seeds, dairy (not fat free), sardines and pilchards with bones, cola drinks, cocoa (therefore all chocolates), whole grain products and legumes.

Eating regular meals of the same size and at the same time daily are still very important in managing blood glucose levels. Fruits should always be eaten with a meal (never on their own) as although they contain natural sugar (fructose) they will still result in a rapid increase in blood glucose levels. This can be counteracted by eating fruits with a meal or snack (e.g. small apple eaten with one slice rye bread with one teaspoon tub margarine and sugar free jam).

The degree of renal impairment will be determined by your doctor (by means of blood and urine tests) and conveyed to you. When renal function is 25 – 30 per cent (moderate impairment) of normal, a moderate reduction of excessive protein intake must be adhered to. This translates to 1 g of protein per kg body weight or 90 g meat/chicken or fish portion at both lunch and dinner. 90g is approximately equal to the size of your palm. High phosphate foods (chocolate containing drinks, nuts and seeds, dairy (not fat free), sardines and pilchards with bones, cola drinks, cocoa (therefore all chocolates), whole-grain products and legumes) must also be taken in limited amounts. Certain fruits and vegetables must also be avoided or consumed in limited quantities. The most important of these to avoid are pumpkin, spinach, olives, coleslaw, pickled onion and vegetables, tinned vegetables, bananas, oranges, grapes, mulberries, paw paws and cherries. The reasoning behind this is that these foods are high in potassium, a type of salt that is involved in muscle contraction and heart function. An excess of potassium and phosphates can cause nausea, vomiting, confusion, fatigue, itching and loss of appetite as well as further kidney damage. It is thus vital to limit intake of these foods.

With severe renal impairment (function 50 per cent of normal) dietary limitation of the above foods becomes even more important to maintain a degree of renal function and quality of life. Protein intake should be reduced to 0, 8 g / kg (60 g meat portion at lunch and dinner – 60 g is approximately equivalent to the size of 2 match boxes). Vegetables should be peeled and chopped into small pieces and then soaked in a large bowl of water for two hours before being boiled. This further reduces the potassium content of your vegetables. Foods high in salt (processed, tinned, canned foods etc) must also be avoided as these can cause water retention which can in itself be dangerous. Carbohydrate (bread and cereals) intake is very important in these patients to ensure that muscle protein is not broken down. Breakdown of muscle protein is associated with disability to perform normal daily activities, lethargy and fatigue.

Diet is very important in maintaining residual renal function and quality of life. It is recommended that all patients suffering from renal disease consult a nephrologist and dietician that has a good understanding of nephrology as this is a highly specified diet that plays a pivotal role in prevention of further renal decline and quality of life.