Uric acid

Uric acid forms when your body breaks down purines. Purines sit in your own cells, which are renewed daily, and in what you eat: meat, offal, shellfish, and by a detour also fructose and alcohol, which drive the breakdown in your liver. What you do not need, your kidneys clear, with a small part leaving through the gut. The value in your blood is therefore the balance of two things: how much you make and how much you get rid of. The problem with uric acid is that it dissolves poorly. Above a concentration close to the upper limit of the normal range it precipitates as needle-shaped crystals, preferably in cool joints such as the big toe, and sometimes in the kidneys as a stone. As long as the value stays below that, nothing happens; it is a threshold effect, and that explains why most people with a high uric acid never get a gout attack and some do. Your report shows uric acid in mmol/l, with one range for men and one for women. Normal is 0.20 to 0.42 mmol/l in men and 0.12 to 0.34 mmol/l in women; women sit lower because oestrogen promotes excretion through the kidneys, and after the menopause their value shifts towards that of men. For anyone with gout a stricter limit applies: under 0.35 mmol/l crystals slowly dissolve.

Uric acid is the value behind gout, one of the most painful joint inflammations there is: a joint, often the big toe, that turns red, swollen and untouchable in a single night. The higher the value and the longer it stays high, the greater the chance that crystals settle somewhere. But a high value alone is not a disease, and most people with a high uric acid never get gout. The reason to know the value anyway is what sits behind it. A high uric acid is, in most people, a lifestyle value. It goes with belly fat and insulin resistance, because insulin slows excretion through the kidneys. It goes with soft drinks and fruit juice, because fructose drives production. It goes with beer and spirits, and with plenty of meat and little vegetables. That is why it often runs alongside high triglycerides, high blood pressure and high blood sugar, and it is one of the earliest values that point that way. Whether uric acid itself damages the vessels and kidneys or only runs alongside is not settled; lowering it with medication in people without gout has yielded little in research. What is settled: the lifestyle that lowers uric acid is the same one that improves the rest of that pattern. Kidney stones are the second reason to know the value: some of them consist of uric acid, and drinking plenty and a lower value help against them. For anyone with gout the question changes. Then 0.35 mmol/l is the limit the treatment steers by, well below what the labs still call normal in men, because crystals only dissolve below that concentration.

The usual causes of a high uric acid are the levers themselves: excess weight and insulin resistance, soft drinks and fruit juice, beer and spirits, plenty of red meat, offal and shellfish, and drinking too little. Then medication: diuretics such as hydrochlorothiazide and low-dose aspirin slow excretion. And the kidneys themselves: anyone filtering less holds on to more uric acid. Rarer are inherited predisposition, psoriasis and rapid cell breakdown, as after heavy exertion or chemotherapy. Rapid weight loss and fasting push the value up temporarily, because ketones slow excretion. A low uric acid is almost always favourable or harmless. In anyone who eats plant-based, is lean and drinks little alcohol it is the ordinary outcome, and in anyone treated for gout it is the goal. Very low values sometimes come from medication that drives excretion, or from a rare inherited trait of the kidneys, and those rarely call for anything. Uric acid responds within weeks to what you change. Soft drinks, juice and energy drinks out, because fructose is the strongest dietary lever. Cut down beer and spirits; wine weighs less. Less red meat, offal and shellfish, more vegetables, legumes and whole grains; the purines in plants barely raise uric acid. Low-fat dairy, coffee and vitamin C lower it a little. Losing weight around the middle works most strongly and longest, provided it is gradual. Plenty of water, certainly with kidney stones. With gout and repeated attacks or tophi, medication joins in, allopurinol first, and then 0.35 mmol/l is the goal. Read uric acid beside your kidney function, creatinine and eGFR, because the kidneys are the exit, and beside triglycerides, blood sugar and blood pressure, which it often rises with. One high value is not gout; gout is diagnosed on symptoms and where needed on crystals in the joint fluid, and during an attack uric acid can even be normal.