The Salt Institute has been engaged in the cyber-debate over the British Food Standards Agency's promotion of salt-reduced diets. FSA released a report yesterday stating that in five years, Britons had reduced their salt intake from 9.5 g/day to 9.0 g/day. A typical newspaper story ran the story this way:

Salt consumption in Britain is still on average 50 per cent higher than the recommended amount, new research has revealed today. Tests on 1,287 adults showed their average salt intake was 9g per day. Although this is adrop from 9.5g when the last tests were done in 2001, the consumption is far higher than the national target of 6g per day, the Food Standards Agency said.

That set off a string of reader comments -- you can read them yourself .

First of out the box was the accusation that salt manufacturers who object that the intervention might entail risks should "tell us which consumers could be harmed by a blanket approach and of course, the evidence?"

OK. We did. I responded:

Two groups come to mind, based on peer-review, published studies: the populations of Mr. Schmulian's Scotland and the population of the United States. The massive Scottish Heart Health study found additional risk for Scots and two studies of the US National Health and Nutrition Examination survey found 20% and 37% greater cardiovascular mortality among those consuming FSA-recommended amounts of salt.

The FSA contention of lower CV risk is based on extrapolations that have not been confirmed in studies of the direct question: will lower salt diets be healthier.

That's why the experts in evidence-based medicine at the Oxford-based Cochrane Collaboration have concluded there is insufficient evidence to recommend universal salt reduction.

That prompted another reader to complain "Your claim about the cochrane institute is wrong," adding that blood pressure is improved by salt reduction. To keep the record accurate and in further response, I added:

The Cochrane review "Advice to reduced dietary salt for prevention of cardiovascular disease" which the Cochrane Library issued in November 2003 (http://www.cochrane.org/reviews/en/ab003656.html ). It concluded:

"Intensive support and encouragement to reduce salt intake did lead to reduction in salt eaten. It also lowered blood pressure but ... not enough to expect an important health benefit. It was also very hard to keep to a low salt diet....

"There was not enough information to assess the effect of these changes in salt intake on health or deaths."

But, the question really isn't about blood pressure, it's about health outcomes. Blood pressure is an interim variable affected by salt. So is insulin resistance, plasma renin activity, sympathetic nervous system activity, etc. What we need to focus on is the net effect: are people healthier? living longer? having fewer heart attacks, etc?

Just keeping the science front and foremost.

Can anyone sort through the confusion of various and conflicting medical journal articles to understand what science is telling us about the basis for sound public health nutrition policy? Perhaps so, venture Drs. Neff Walker of UNICEF and Jennifer Bryce and Robert E. Black of Johns Hopkins University in the current issue of The Lancet, "Interpreting health statistics for policymaking: the story behind the headlines ." They explain:

Politicians, policymakers, and public-health professionals make complex decisions on the basis of estimates of disease burden from different sources, many of which are "marketed" by skilled advocates. To help people who rely on such statistics make more informed decisions, we explain how health estimates are developed, and offer basic guidance on how to assess and interpret them. We describe the different levels of estimates used to quantify disease burden and its correlates; understanding how closely linked a type of statistic is to disease and death rates is crucial in designing health policies and programmes. We also suggest questions that people using such statistics should ask and offer tips to help separate advocacy from evidence-based positions. Global health agencies have a key role in communicating robust estimates of disease, as do policymakers at national and subnational levels where key public-health decisions are made. A common framework and standardised methods, building on the work of Child Health Epidemiology Reference Group (CHERG) and others, are urgently needed.

Just because it's "in black and white" -- even in a bolded headline, doesn't make a statement scientifically valid. Everyone claims their conclusions are "evidence-based," but we need to follow careful rules to understand just which "evidence-based" conclusions are, in fact, "evidence-based."

Two themes of frequent mention here are the crucial importance of quality evidence and a laser-like focus on health outcomes. Others use their own issues to raise these points as well, reinforcing the building pressure for action.

An example is the recent column "Medical Information: The Good and the Bad " by Dr.s Michael Arnold Glueck and Robert J. Cihak aka "The Medicine Men."

Dr. Cihak asks:

What should be done, if anything, about the flood of medical information from news stories, popular magazines, TV shows, advertising, and even our own doctors?

Is information overload even a bad thing?

Moreover, are we missing the forest while looking at the trees? Very often, I'd say yes.

It's often best to ask, "What are we really concerned about?" For example, too much cholesterol in the blood can lead to hardening of the arteries, which can lead to plugged-up arteries in the heart or brain, resulting in a heart attack or stroke.

The effect of the abnormally elevated cholesterol level is the concern, not the cholesterol itself, because lowering abnormal cholesterol levels can reduce the likelihood of disability or death from blocked arteries.

So the goal is to prevent illness, not to reduce cholesterol for its own sake. And, there are always tradeoffs. Taking medicine takes time, money, and other resources away from other uses. Plus, the medicine might not work or even cause additional medical problems.

The same dynamic pertains to the health impacts of dietary salt. The public is being fed an alarmist diet of concern about blood pressure when that is but one of several impacts of restricting dietary salt. Others include increasing insulin resistance, skyrocketing plasma renin activity and stimulated sympathetic nervous system activity. So the Salt Institute's been urging HHS to undertake a study of the health outcomes of salt-reduced diets using this same argument. If you read the above quote, substituting "blood pressure" for "cholesterol" and you'll see what I mean: "The effect ... is the concern, not the cholesterol) itself, because lowering abnormal cholesterol levels can reduce the likelihood of disability or death from blocked arteries. So the goal is to prevent illness, not to reduce cholesterol for its own sake. And, there are always tradeoffs. Taking medicine takes time, money, and other resources away from other uses. Plus, the medicine might not work or even cause additional medical problems."

We couldn't say it better -- though we tried . Thanks as well, doc, for your cautionary summary: "Cookie-cutter approaches are dandy for cutting cookies but not for dealing with human beings."

With this provocative title for its March 2007 featured article, the UC-Berkeley Wellness Letter caught our attention, particularly because they mentioned the Salt Institute. Because it may have caught others' attention, these thoughts to correct some misinformation in the article.

MythStatement: "As concern (with salt intake) has faded, people have been eating more salt. Since the early 1980s, U.S. per capita salt intake has risen by about 50%."

Fact: US food salt sales entering the 1980s were a shade over 1 million tons. Today they are 1.586 million tons -- up about 50%, right? But not "per capita." The US population in 1980 was 227 million; today it exceeds 300 million, up over 32%. And that is "sales," not ingested salt. Looking at the baseline data of entrants to clinical trials who are tested for 24-hour urine sodium, there is no evident increase in per capita sodium intake over time.

MythStatement: "Many large observational studies over the years have linked a high sodium intake to high blood pressure and increased deaths from heart attacks and strokes. For example, the Intersalt study looked at 10,000 people in 32 countries and concluded that high salt intake was directly related to hypertension and deaths from stroke." The article then states that pro-salt critics have found methodological problems with Intersalt.

Fact: Intersalt was a great study, though not an intervention trial. The primary hypothesis of the study was that salt intake was directly related to blood pressure. Contrary to the Wellness Letter, the study did not confirm this hypothesis; neither for systolic blood pressure (the primary hypothesis) nor diastolic blood pressure (the secondary hypothesis). There was no relationship. The Salt Institute has always considered Intersalt a high quality study. Salt opponents did too, until the results were announced; after that, they began to find reasons to back away from its findings. As for other "large observational studies ," none have found higher incidence of cardiovascular events nor higher CV mortality on diets with US-levels of salt.

MythStatement: "It's much harder to dismiss the research on the DASH (Dietary Approaches to Stop Hypertension) diet, which consists of fruits, vegetables, and whole grains, plus small servings of meat and dairy. It also provideds a lot of potassium, magnesium, and other minerals that help control blood pressure. DASH comes in two versions -- one with 2,300 milligrams of sodium a day, the other with 1,500. Both diets lower blood pressure in healthy people, but most dramatically in those with hypertension. The lower-sodium version lowers blood pressure even more. "

Fact: Where to start? The Salt Institute has endorsed and strongly promoted the DASH Diet since it was first reported in 1997. It is not properly described in the Wellness Letter. It is high in fruits, vegetables and dairy products and low in meat -- not reduced in dairy as stated. In fact, half the blood pressure benefit is from the dairy. The DASH Diet is also not reduced in sodium at all. A second "DASH" trial was held reducing sodium to 2,300 mg and 1,500 mg. Judge the results for yourself. As the Wellness Letter points out, those with high blood pressure benefit the most. The original trial found they achieved a drop of 11.4 mm/Hg in systolic blood pressure when on the DASH Diet (with no sodium reduction). When DASH Dieters were placed on the 1,500 mg salt-reduced diet, they achieved an 11.5 mmHg SBP reduction. We call that statistical noise. We think it's clear the benefit is conferred by the improved quality of the DASH Diet (11.4 mmHg) and the additional contortions to reduce sodium by 60% produced only an insignificant change (0.1 mmHg). Furthermore, while the nutrients stated are likely to be responsible for erasing the "salt sensitive" blood pressure response, the trials were for foods, not nutrients.

MythStatement: Finland achieved a decrease in deaths from strokes and heart attacks over the past 30 years by reducing dietary salt.

Fact: The US has reduced its rate of reduced cardiovacular events and mortality over this same time span by the same amount without reducing dietary salt (the Wellness Letter even says salt intake in the US has increased).

MythStatement: "Here's what the salt industry advises: There's no ironclad evidence a high salt intake is bad, so don't worry. Eat what you want, and enjoy yourself. Help us make a lot of money out of salt."

Fact: We have no evidence that they're still smoking stuff on the Berkeley campus; this statement could just be a coincidence. The Salt Institute has long supported "moderation" in sodium intake, supporting the US Dietary Guidelines until 2000 when the Guidelines left this safe harbor. It may be that high-salt diets such as in Japan are problematic; experts disagree (see previous blog ), but we are at the polar opposite of hedonists who say "eat what you want." The answer, as we've repeatedly testified, is that we need to improve the overall quality of the diet, particularly improving the mineral density of the diet (more calcium, magnesium and potassium).

MythStatement: "Most people can quickly get used to a lower-sodium diet..."

Fact: Reducing dietary salt is NOT easy. In the DASH Diet, they achieved compliance by providing free food. In the Trials of Hypertension, with heavy hands-on encouragement and coaching of highly-motivated volunteers, salt reduction was reduced by about a third over the three years of the trial. (Note: during that three years, the body adjusted and blood pressures returned to their former levels -- how come the Wellness Letter didn't mention that?)

There are more assumptions and leaps-of-faith, but this gives you an idea of how a supposedly unbiased and expert review can go awry when confronted with the near-religious zeal to cut salt.

The International Journal of Epidemiology has just published (February 2007) "Dietary patterns and cardiovascular disease mortality in Japan: a prospective cohort study ." Taichi Shimazu and colleagues studied 40,547 Japanese over seven years and reported on the 801 cardiovascular deaths in the group. They reported, unsurprisingly, that the Japanese dietary pattern is high in sodium (my note: possibly the highest in the world). Their conclusion: "The Japanese dietary pattern was associated with a decreased risk of CVD mortality, despite its relation to sodium intake and hypertension."

The authors point out that while the Japanese consume more salt than western diets, their age-adjusted mortality due to cardiovascular disease is about 40% lower than the UK and about 30% lower than the US. They point out that earlier studies of particular nutrients or foods in the Japanese diet (such as sodium) have generated great concern among public health activists, but when the entire diet is considered, those associations disappeared.

By our count, that's 14 studies relating health outcomes to dietary salt . None confirm any health benefit for lower salt intakes in the range of the American diet and of the two in high-salt-consuming Japan, this one finds no benefit while the other found reduced stroke incidence on levels where the "low salt" consumers ate more salt than the U.S. average. See our online discussion .