With the US presidential campaign focusing so much on character (Obama's embrace of his racist preacher, Clinton's embellished "experience," McCain's unpredictable "maverick" tendencies), one can lose track of some very real issues that divide the candidates. These aren't limited to the economic issues, but that's today's focus. This week Congressional Democrats tied themselves squarely to the anti-free trade crowd with Speaker Pelosi refusing a vote on the Columbian free trade agreement (which Bill was for before Hillary was against). Hovering just under the radar is, aguably, the biggest divide: the Bush tax cuts. Democrats only accepted the cuts because they included in the package a provision that automatically restores the original tax rules and rates at the end of 2010 unless another law supersedes the one on the books. Democrats have loudly proclaimed the tax cuts as a Republican give-away of the federal treasury while Republicans crow that the cuts ended the recession that began in the last year of the Clinton presidency and is needed to sustain our economic growth.

The April 21 edition of National Review (subscription required) examines the historic tax take of the national governments of the US and its OECD partners. An excerpt illustrates, but please keep reading because I'd like to draw a parallel to an issue regarding salt. NR's Kevin Hassett wrote:

As reporters sort through these debates, they must write at a far lower level of sophistication than that of the studies in question. Since New York Times readers don't know econometrics, they are instead offered pseudo-analysis. The economists who agree with supply-side economics are generally described in terms to suggest that they are nut jobs. Those who disagree with supply-siders are "distinguished professors" or "senior fellows" at "nonpartisan" institutes. We are invited to judge, not the arguments, but the reasonableness of those who make them - and it is clear what our judgment is supposed to be. But interestingly enough, it's possible to determine with some precision whether a policy has been formulated by nut jobs. To see how, consider the following statement: "U.S. fiscal policy in recent years has deviated wildly from fiscal policy in other developed nations." If that's true, one can presumably make the case that U.S. policymakers have ignored policy norms. (This is of course just what one would expect nut jobs to do.) If the claim is false, however, then it's rather harder to claim that American fiscal policy is in the hands of kooks.

Let's apply that method to the question of income-tax cuts. The nearby chart depicts recent trends in the share of GDP that governments collect through income taxes. The purple line represents the U.S.; the blue line represents the average for large developed nations in the OECD, excluding the U.S. And the story is clear: For most of recent history, the U.S. share was about equal to that of the OECD generally. It did deviate wildly at one point - in the second term of President Clinton, when the U.S. was collecting a markedly higher percentage of its GDP in income-tax revenue than were its fellow OECD members. But the Bush tax cuts returned us to normalcy.

The "salt" issue? The policy debates over whether the entire population should be encouraged to reduce dietary salt often comes across as a debate with an empty chair. Proponents of this intervention are content to point to their accepted "expert" status and insist that their informed opinion should determine the policy question. These are the "distinguished professors" etc of Mr. Hassett's narrative. By no means all, but some of these activists have tried to marginalize the equally-distinguished experts who argue that no evidence shows low salt diets will improve public health. They duck the issue and try to dismiss opposing scientists as somehow less informed or, surely, more biased -- in short, akin to the "nut jobs" Mr. Hassett describes (though none of them have stooped that far to date).

The parallel? Mr. Hassett graphs the data. That's what we should be doing too: looking at the data. Those data can tell us a lot more than the "expert" opinion of those who cannot or won't deal with the real evidence. Let's stop talking with the empty chair. The public deserves better.

The April 10 issue of the Harvard Medical School 's HealthBeat offers "diet tips for lower blood pressure." We wish they'd wake up that the real issue isn't "blood pressure," but "improved health." Still, the glimmerings of awakening are discernible. Let me add boldface to the relevant parts of the complete text for the tip: "Consume less salt":

Doctors first noticed a link between hypertension and sodium chloride - the most common form of dietary salt - in the early 1900s, when they found restricting salt in patients with kidney failure and severe hypertension brought their blood pressures down and improved kidney function.

Federal guidelines advise people to limit sodium intake to 2,300 milligrams (mg) per day - about the amount in 1 teaspoon of table salt. Yet Americans typically consume 1 to 3 teaspoons, or as much as 7,200 mg a day. This fact, coupled with the high prevalence of hypertension in the United States, led researchers to assume that salt overload was the culprit.

As it turns out, this may or may not be true. Nearly 50% of people who have hypertension are salt-sensitive, meaning eating too much sodium clearly elevates their blood pressure and puts them at risk for complications. In addition, people with diabetes, the obese, and older people seem more sensitive to the effects of salt than the general population. However, the question of whether high salt consumption also puts generally healthy people at risk for hypertension is the source of considerable debate. Regardless of whether high salt intake increases blood pressure, it does interfere with the blood pressure-lowering effects of antihypertensive medications.

Baby steps forward.

Newspapers today reported on work being carried out at Glasgow University on the relationship of aldosterone to blood pressure . The research was presented at the annual Society for Endocrinology BES meeting in Harrogate , UK. The initial research indicates that in older people, higher levels of aldosterone in the bloodstream are associated with high blood pressure .

In a paper entitled, "Aldosterone and cardiovascular function: a lifetime of damage ," Dr. John Connell , who is Professor of Endocrinology at the University of Glasgow and Head of the of the Medical Research Council's Blood Pressure Group, based in the British Heart Foundation's Cardiovascular Research Centre in Glasgow described how an excess of aldosterone greatly increases the risk of stroke and heart failure, thus explaining the results of several previous research studies that revealed more cardiovascular patients dying on low salt diets than on regular diets.

Professor Connell said:

"Aldosterone is a key cardiovascular hormone. The higher the level of aldosterone in your blood, the more likely it is that you will suffer from high blood pressure, which will increase your risk of suffering a heart attack or a stroke."

The research revealed that in older people, higher levels of aldosterone in the extracellular fluid are associated with high blood pressure. In young adults, high aldosterone levels predict that they will be more likely to develop hypertension later in their lives. There are a number of factors that determine elevated aldosterone levels in humans, including low birth weights, genetics and diet. More specifically, insufficient salt intakes will stimulate the renin-angiotensin-aldosterone system (RAAS) to produce more aldosterone in order to conserve the body's cache of sodium in order to retain osmotic balance.

Elevated aldosterone levels mean that throughout life, certain individuals will be more prone to developing high blood pressure, arterial stiffness and cardiovascular disease. Connell's previous research indicated that aldosterone may be a causal factor in 10% of UK patients with high blood pressure*.

It is difficult to understand why the UK Food Standards Agency, the EU Commission and the Health Canada are all deliberately ignoring this research in their drive to reduce the levels of salt consumed. The mechanistic research work on the malignant role of elevated aldosterone levels upon the cardiovascular system brings far more weight to the salt and health outcomes question than the highly promoted, yet scientifically flawed epidemiological studies on salt and blood pressure.

The human body is an organism governed by biological mechanisms and no amount of bias, hype or imprudent policies will change this. ______ *Connell, J.M.C., Davies, E. 2005. Journal of Endocrinology, 186, 1-20.