I have pointed out that the recommended US diet specifically seeks to correct all five of these risks and we should recommend it to all of our stone patients unless contraindicated by some specific problem.
But I have not as yet shown to what extent we as a nation eat a diet deficient in calcium and potassium and excessive in refined sugar, sodium, and protein. In other words I have not as yet quantified the extent of the problem that stone forming patients face.
Here is evidence from a large body of expert scientists.that we do in general eat an unsatisfactory diet.
The painting ‘Peasant Wedding’ by Pieter Brueghel the Elder (1526/1530–1569 – Google Art Project) hangs in the Kunsthistorisches Museum, Vienna. I chose it to reflect not gluttony, which is almost a cliche in 16th century art, but fullness or richness of means and possibility.
It presents a lavishness like our excesses of sodium and sugar and protein, and a paucity – this is a scene of multiple classes of people and a gradient of wealth – as we are poor in calcium and potassium.
WHERE WE GET THE INFORMATION FROM
The National Health and Nutrition Examination Survey (NHANES) describes itself so perfectly, I merely quote their blurb:
“The National Health and Nutrition Examination Survey (NHANES) is a program of studies designed to assess the health and nutritional status of adults and children in the United States. The survey is unique in that it combines interviews and physical examinations. NHANES is a major program of the National Center for Health Statistics (NCHS). NCHS is part of the Centers for Disease Control and Prevention (CDC) and has the responsibility for producing vital and health statistics for the Nation.
The NHANES program began in the early 1960s and has been conducted as a series of surveys focusing on different population groups or health topics. In 1999, the survey became a continuous program that has a changing focus on a variety of health and nutrition measurements to meet emerging needs. The survey examines a nationally representative sample of about 5,000 persons each year. These persons are located in counties across the country, 15 of which are visited each year.”
The NHANES 2007 2010 survey is the most recent, and from it I have brought here the main results concerning kidney stone and bone disease.
A REVIEW OF THE IDEAL STONE FORMING DIET
In this article, I simply state the scientific conclusions about key diet factors that concern stones and bone disease in stone formers. The data are summarized in a prior article.
LOW CALCIUM INTAKE
Because idiopathic hypercalciuria (IH) is highly prevalent among stone formers, and because people with IH are in negative calcium balance – losing bone calcium – on diets with more than sufficient calcium to support bone balance in people without IH, a low calcium diet can deplete bone mineral and predispose to fractures.
Urine oxalate is strongly dependent on diet oxalate content when diet calcium is low, but when diet calcium is high urine oxalate falls. For this reason, a low calcium intake will raise urine oxalate excretion.
HIGH SODIUM DIET
Urine calcium rises with urine sodium in both normal people and those with IH, but far more briskly in those with IH than normal. So a high sodium diet is ideal to raise urine calcium, thereby increasing urine supersaturation and stone risk.
Although not studied in IH as yet, high sodium intake prevents even high calcium intake from achieving positive bone mineral balance at least in perimenopausal women. We lack a trial of diet sodium and calcium in IH bone disease.
HIGH SUGAR INTAKE
In everyone, but especially in people with iH, sugar loads raise urine calcium abruptly and markedly. The spikes of high urine calcium will raise urine supersaturations and foster crystal formation. Habitual sugar use has an excellent potential to help deplete bone mineral because calcium is not usually present in highly sugared foods and beverages.
LOW POTASSIUM INTAKE
Diet potassium is largely from fruits and vegetables, and comes not as the chloride salt but mainly as the counterion to organic molecules whose metabolism produces bicarbonate – such as citrate. Bicarbonate production down regulates the renal citrate transporter in normal people so urine citrate rises. Citrate inhibits stone formation by binding calcium thereby reducing supersaturations, and by directly interfering with nucleation and growth of calcium crystals.
HIGH PROTEIN INTAKE
Diet protein raises urine calcium. How it does so may be via the net acid load produced by oxidation of sulfur in cystine and methionine but recent evidence suggests it is the protein itself. Whichever way protein acts, the higher urine calcium can promote stones. Whether protein loads reduce bone mineral is a contested issue to date.
WHAT DO I MEAN BY LOW AND HIGH?
MUCH SCIENCE YIELDS REASONABLE ESTIMATES OF HEALTH NEEDS
With great expense of effort and skill the 2015 Dietary Guidelines Advisory Committee derived from available science to date optimal intakes of these and all other relevant nutrients for promotion of the health of the American people. I will not review evidence concerning the qualities of the people involved in that work, but simply accept that they were numerous and expert, and probably have provided about the best and balanced interpretation of the science possible.
By high and low I mean in relation to the findings of that group. In the graphs here and to follow the upper and lower bounds of the optimal intakes are shown by bars.
This and all other graphs are from the 2015 – 2020 diet guidelines.
Dairy products (Dairy) are the chief source of calcium, and over 80% of Americans eat less than (orange bar) the recommended amount (1,000 to 1,200 mg/d depending on age and size).
Sodium is chiefly from additives, and over 80% of Americans eat more than the tolerable upper limit of 2,300 mg/d.
Added sugars are those that raise urine calcium, and about 70% of Americans eat more than the recommended amount (<10% of total carbohydrates/d).
Diet potassium is mainly from vegetables and fruits, and about 80% of Americans eat less than the recommended about of these foods and therefore less than the recommended 4,300 mg/d of potassium with its accompanying organic anions.
Diet protein is not so unbalanced as the rest, with only 55% of people eating more than ideal.
Oils and saturated fats may affect vascular disease but are irrelevant to stones and bone disease so I dismiss them here.
OUR DIET FOSTERS STONES AND BONE DISEASE
i hardly need to comment or repeat myself. Compared to what we need for health we eat too little calcium and potassium, and too much added sugar, and sodium. We also, in some subgroups, eat too much protein.
ANALYSIS BY AGE AND SEX
In this and the following graphs, all from the same 2015 – 2020 diet guidelines, the blue bars are the range of recommended intake.
In both sexes, calcium intake is low almost throughout life, but increasingly so with age. Three cup equivalents of dairy products are estimated to provide the needed 1,000 to 1,200 mg of calcium, meaning that most adults, eating half of that or less, get about 500 to 600 mg/d of calcium.
Bone mineral balance is not well maintained in IH at even 1,000 mg/d of calcium. At lower levels, negative calcium balance would be the general rule. Urine oxalate will be higher at low compared to high calcium intake, a major factor in stone risk.
Among men, more than women, intakes soar with age, to over twice the upper limit (Graph below). That upper limit itself is hardly an ideal. For middle age people, those with high blood pressure, and others specially sensitive to sodium the ideal is 1,500 mg/d.
The high sodium is from additives. Creatures that walk on the earth, or swim in the salt sea, or in the lakes and running rivers have some sodium in them for us to eat, but little enough that if we add none from salt mines our daily intake would be below the ideal of 1,500 mg/d.
Most plants contain so little sodium that an all plant diet with no milk products would provide just enough.
Massive trial data have gradually pushed back all reasonable doubt that it is sodium excess and potassium deficiency more than any other factors that account for the rise in blood pressure with age. High blood pressure is a massive and remediable risk factor for stroke, heart attack, heart failure, and kidney disease.
Experts have concluded that refined sugar is a main cause of obesity and diabetes. For us, it is a problem of hypercalciuria.
Men and women are equal in their sugar excess. From ages 4 – 8 on, and through into late middle age and old age we eat added sugar, as a percent of total carbohydrates, at nearly twice the levels we should.
Because the two sexes eat about the same amounts of fruit but men are larger and should eat more, men are relatively more deficient.
Fruits have virtuous molecules that experts say protect against diseases such as hypertension and perhaps cancer.
From the point of view of stones, their high content of potassium would be valuable because their potassium is mostly with organic molecules that are like citrate in being metabolizable, and their metabolism produces an alkali load that raises urine citrate.
In general we eat protein mostly in line with recommendations. Men are perhaps high, women are perhaps a bit too low. Experts maintain that too much of the protein is from land animals rather than fish or from plants, but from a kidney stone point of view I have no reason to make this distinction.
HOW GOOD IS THE EVIDENCE?
THAT OUR DIET FOSTERS STONES AND BONE DISEASE
I have exhausted myself parsing the data on calcium, sodium, sugar, anions, and protein and can do no more. This linked article reviews what is detailed in many other articles on this site, and the latter are linked out to the primary peer reviewed literature.
Nothing is certain in this world, this life. Even so we have to act based on reasonable evidence. The evidence is reasonable. Read it for yourself and make your own evaluation.
The ideal levels that the guideline committee proposes for calcium, sodium, potassium, calcium, and protein are in line with what the science of stone disease says would reduce kidney stone risk and risk of bone loss in patients with IH.
THAT OUR PRESENT DIET IS AS DEPICTED
I have no expertise in the kind of massive population sampling that drives NHANES and no ability to judge the quality of the NHANES scientists or the work they present. The sheer numbers of qualified scientists involved, and the longevity of the project, make me satisfied to some extent. Because salt and sugar are contentious matters in the US expert critics abound who would by now have unearthed and publicised defects in the work. I accept it as reliable. I might add that in my clinical experience stone formers commonly have many of the poor dietary habits reported in NHANES.
We eat and have long eaten in a way as if designed to cause stones and bone disease.
The diet for stone prevention and the bone disease of idiopathic hypercalciuria is more or less the diet for everyone. Physicians should foster the US diet recommendations for stone formers, and stone formers should adopt the diet for their own benefit.
Given the quality of the science that drives NHANES and the diet guideline committee, we all might be better off following the US diet recommendations, stone formers or not.