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Cordelia’s Cautionary Tale: How Our Love of Salt Has Made Phosphate the New Sodium

fig 2Painting of King Lear weeping over the body of his daughter, Cordelia. 18th century oil painting by Irish painter, James Barry.

Fig 1Failing to recognize our love of salt can be our undoing. It is as true in literature as it is in life. In the opening scene of Shakespeare’s King Lear, the aged king asks his three daughters to quantify their love for him. The older daughters, Goneril and Regan, who ultimately will betray their father, flatter him with hyperbole. The youngest daughter, Cordelia, who truly loves him declines to answer, thinking it a silly question. When Lear insists upon a response she offers a curious reply, “I love you…as fresh meat loves salt.” Taking affront, he casts her out and divides his kingdom between his two daughters. Bad choice as it turns out. Later in the play, Lear comes to understand that meat does love salt; rather people love meat only if it is salted. He also comes to learn that false praise is hollow and is ultimately reunited with the virtuous but ill-fated, Cordelia.

Shakespeare did not discover salt’s importance; he merely enshrined it in literature. Salt has long been central to civilized life. We work to earn a salary, a word derived from the Latin: salarium, meaning money to buy salt. Modest consumption of salt is healthy and even supplemental salt, meaning sodium chloride, in moderation is safe. However, modern society’s consumption of salt by the teaspoon is as harmful as Lear’s love of excessive flattery.

Although salt is not new to the human food chain, only once it was commoditized did consumption at high levels occur. The introduction of sodium additives into human food supplies increased the average daily consumption 10-fold, from 400 mg/day to over 4000 mg/day. In 2013, excessive consumption of sodium chloride is both common and unhealthy. High sodium diet puts us at risk of stroke and myocardial infarction, leading health agencies to call for reduced sodium in our diet, particularly in patients with hypertension. After three decades of lobbying, food is now labeled to show sodium content, giving consumers the information to make the healthy choice. Three decades of advocacy and we have success! …Not so fast. Turns out sodium chloride has a sister salt, sodium phosphate, which has joined the party.

fig 4Dr. Rachel Holden (right), Associate Professor in Nephrology, at Queen’s University recently discussed an emerging health concern that is an unintended consequence of reducing dietary sodium: the stealth introduction of phosphate salts into the food chain.

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In her Medical Grand Rounds presentation on November 14, 2013, she revealed that the food industry has replaced the sodium in food to garner the coveted Heart and Stroke Foundation’s H&SF healthy choice label, with another salt that is equally harmful: phosphate.

The false comfort of low sodium foods: As Cordelia said, meat loves salt, so if there is no sodium, something else must be added. That something else is phosphate. Dr. Holden’s research suggests that the addition of phosphate to food leads to cardiovascular disease and makes the case for labeling phosphate content in the same way we label sodium content. Dr. Holden is certainly not alone in the call for making phosphate content in food more clear to consumers.

PrintUnfortunately, the rapid increases in phosphate are covert. Regulatory agencies are slow to recognize harm. Oddly, the onus of proof when it comes to food additives is on science to show that a label is required to indicate harm, rather than on industry to first establish that a potential additive is safe. More unfortunately, high phosphate levels predict the development of cardiovascular disease.

Phosphate is being added to foods, particularly fast foods (see Figure below)

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Phosphate is also being added to meat to enhance its perceived moistness. Dr. Holden reported that more than 40 million pounds of phosphate additives were used annually by the meat industry during the 1970s. The baking industry uses the highest quantities of phosphate additives. Baked goods contain nearly 10-fold higher amounts of phosphate additives than meat products (From: Phosphates in Food. CRC Press, Inc, 1991)

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The problem as outlined by Dr. Holden is not just that there is a stealth augmentation of our diet with ten times more phosphate; it is also that the phosphate is being added in forms that promote absorption, thereby increasing the likelihood of deposition in inappropriate places, such as blood vessels. Take the example of processed versus natural cheeses.

To start, the Kraft Singles cheese has six times the phosphate content of natural Brie (590 m g vs 94 mg). To make matters worse, the emulsifiers and pH altering agents in the processed cheese cause 100% of its phosphate to be absorbed (vs 60% of phosphate in the Brie).

You can never be too rich: Of course just like salt, the phosphate story involves money. The Brie is better for you but it costs twice as much as the processed cheese slice. It turns out that salt, whether sodium or phosphate, is cheap. In a paper by the CRIC study group it is clear that the richer you are, the lower your phosphate levels.

fig 13The fate of phosphate: Dietary phosphate has two fates: it can be eliminated, passing through the intestine unabsorbed, or it can be absorbed. If absorbed, it is either eliminated by the kidney or retained and deposited in the tissues. While phosphate is a key component of healthy bone, excessive phosphate absorption leads to calcification where it ought not occur: in our blood vessels.

This vascular calcification is something physicians see all too commonly. It leads to hypertension and an increased risk of death. While the problem is greatest in patients with kidney disease, because they can’t eliminate phosphate, it also seems to adversely affect people with normal renal function.

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Elevated tissue phosphate levels trigger a fascinating but lethal process in blood vessels in which smooth muscle cells in the blood vessel wall change their gene expression and transform into bone making cells (osteoblasts). Once this occurs, calcium-phosphate (bone) is deposited in the wall of the vessel leading to many cardiovascular diseases (See figure at right: Mechanism of phosphate induced vascular bone formation (Holden, R)).

Dr. Holden is not alone in her concern regarding dietary phosphate. In an article entitled, ‘Phosphate Additives in Food-a Health Risk’,  Dr. Eberhard Ritz suggests, Comprehensive labeling of phosphate additives in food—ideally, with a ‘traffic-light’ scheme—would also be desirable, as would a quantitative restriction of phosphate additives.”

This table reveals some surprises – those of you who love your Colas, take note!

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Instead of the Coke/Pepsi challenge, take the Phosphate-Sodium Challenge: Which images in this grid show phosphate?

fig chartAnswer: B, D and F

So what is the solution? It is multifactorial. Avoid eating at fast food restaurants, try and prepare meals from fresh ingredients and ultimately we need to lobby regulatory agencies to get phosphate tracked on food labels, just like sodium. Most agencies believe the levels dietary phosphate consumption should be < 1 g/day.

I love the solution proposed by Dr. Holden: she espouses the 100-mile Diet.

Her advice is to eat food produced within 100 miles of where you live. These foods are less likely to be supplemented with either hidden sodium or phosphate. This is a diet and a social movement..and while I recognize the complexity, it may be the best way to avoid eating things that are both harmful and hidden. In our own Department we have a practitioner of this philosophy: Check out Fat Chance Farmstead (a local producer of organic fruit and veggies) run by Jen Valberg and her partner Josh Suppan.

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Dr. Archer, Dept. Head
Dr. Archer, Dept. Head