(1) ... While I will answer this here, I am conscious of butting in on LeeAnn's page and I don't want her to think I am trying to become a dietitian ... so, perhaps, if you want to ask me stuff, its best at my page and not LeeAnn's page. Further, LeeAnn is going to be more comfortable answering diet-related questions than I am.
(2) ... I am also drifting from (far away from) my area of comfort, as I am neither a trained dietitian nor particularly switched on to diet as a nephrologist.
But, that said, I think I can answer these ... and I hope LeeAnn will forgive my intrusion into her page one more time ... so, here goes:
Phosphorus … (read phosphate) … and cheeses
Phosphorus is a mineral naturally found in food. Indeed, almost all foods contain phosphate!
Remember what a farmer treats his pasture with? … super-phosphate! His crops and pasture absorb it – they need phosphate to grow (all plants do) – and then the meat we eat comes from the animals that eat the pasture that the farmer has ‘spiked’ with super-phosphate! It is a ubiquitous mineral. It reminds me of the old nursery rhyme about 'the house that Jack built'!
In the body, phosphorus combines with calcium to make calcium phosphate – an integral component along with calcium carbonate in the formation of bones and teeth!
Phosphorus is also the engine that drives our energy production … it is the foundation for the absolutely vital, life-giving energy battery for cells - a co-enzyme called ATP (adenosine tri-phosphate).
One internet source http://hyperphysics.phy-astr.gsu.edu/hbase/biology/atp.html describes ATP as: “the energy currency of life … the high-energy molecule that stores the energy we need to do just about everything we do. It is present in the cytoplasm (cellular ‘soup’) and nucleoplasm (nuclear ‘soup’) of every cell. Essentially all the physiological mechanisms (of the body) that require energy for (their) operation obtain it directly from the stored ATP".
Put bluntly, without phosphate – we’re utterly stuffed!
The major food sources of phosphorus include cheese, milk, meats, whole grains, legumes and nuts. Processed foods, especially soft drinks (= bad, bad sources of bad, bad phosphate) are also very high in phosporus and are best avoided.
We NEED phosphate!
But, normally, we are able to balance the amount of phosphate we take in through our diet by excreting any excess via the kidneys. But ... when kidney function is lost, we lose the escape valve. That is where a conventional dialysis patient runs into a lifestyle agony! … more phosphate is consumed in a normal palatable diet than conventional dialysis can remove.
The only two options are to then (1) limit the dietary intake (= unpleasant dietary choices) or (2) to play tricks on phosphate by ‘binding’ ingested phosphate in the gut by the use of ‘binders’ so that it can’t be absorbed and passes out, unabsorbed, in the pooh (= unpleasant pills and pooh like limestone)!
We now know that more dialysis is able to remove enough of the ingested excess (conventional dialysis just cant!) to restore a balance between dietary intake and dialysis loss such that binders are needed and ‘poohing’ becomes pleasant again!
Back to cheeses … and there are two things to be said about cheese.
First, cheese is made from milk – and milk products are almost like fluid calcium + fluid phosphate (plus some fats). Most mammals (including us) are designed to feed their young with milk to transfer immune proteins, to ensure phosphate is given ... to make ATP and its precursor phosphate co-enzymes ADP and AMP (‘D’ = di and ‘M’ = mono) ... and to help build strong bones in their young. So – cheese has to be a high phosphate source as it is, in effect, concentrated and solidified milk!
Now … some cheeses have a higher phosphate content than others: Swiss (605mg/100gm), Gouda (564mg/100gm), Cheddar (512 mg/100gm), Mozzarella (463mg/100gm), Monterey Jack (444mg/100gm), Fetta (337mg/100gm) and Brie 188mg/100gm).
Why? I suspect the answer may lie in the following:
Second, phosphates are useful as emulsifying agents in the preparation of dairy products … including (and especially) processed cheeses. Phosphate sequesters (stablilises) calcium in cheese and solublises the protein in the milk base. It helps to increase the hydration and swelling of the cheese and to emulsify (suspend) the fat content. Finally, it helps to adjust and stabilize the acidity (pH) of the cheese. As a result, sodium phosphate is hugely important in cheese processing. While this is not meant to be a treatise on cheese-making, you will be beginning to get the point ...
Some ‘types’ of cheese need more (or less) phosphate to ‘emulsify’, ‘solublise’, ‘stabilise’, ‘hydrate’ and ‘pH-adjust’ than others. Some cheeses are more concentrated (compacted) eg: cheddar, than others.
Here-in, I think, lies the major point of difference in their phosphate ‘load’ … especially for the dialysis patient.
Solution #1: avoid cheeses for their phosphate content
Solution #2: seek better dialysis
If I were a dialysis patient (and I adore cheese – especially the French and Australian Blues), I know which of the choices, #1 or #2, that I’d be going for! This again underpins my preference for longer, more frequent dialysis ... and isn't is odd how everything leads me back to this!
Dried fruit … and it’s not just phosphate, but potassium too …
Again, I am not a dietician, but I think the amswer here lies in a 'volume' issue - and volume of food vs my usual gripe about fluid volume.
There isn’t more potassium or more phosphate in a handful of dried apricots – or whatever dried fruit you might eat. It's just the same amount as in the original fruit … it's just been dessicated!
A handful of dried apricots might be, what? … 6-8 apricots? Easy peasy! Down the hatch without another thought! It's just a mouthful, really.
But ... 6-8 normal apricots? … who ever eats that many? Most would stop at one or two at most.
So … dried fruit sneaks up on you! A handful or two is no problem The same, off the bush, and your tummy would be popping!
MooseMum ... I hope that helps to explain it for you. Its kind of a back-woodsy bit of theory – but I think its right. Again, though, perhaps you should ask this of LeeAnn, rather than me, for she knows much more about it than I do.