Take-home Messages:

• About half of the morbidity associated with blood pressure (BP) is associated with levels below what is generally defined as hypertension.
• Therapy should be guided by risk, meaning individuals with multiple risk factors may benefit from better BP control even if they are in the prehypertensive range.
• Population-wide interventions, targeting sodium content in food, for example, can be effective.

May is National High Blood Pressure Education Month. Awareness is getting better, but the U.S. Department of Health and Human Services still has their work cut out for them: of the 68 million in the US with hypertension, fewer than half have it adequately controlled.

And it is far from being just one country’s problem: Vascular disease is the leading cause of death worldwide and hypertension is the leading cause of premature mortality. The World Health Organization notes that while hypertension guidelines have been developed for most countries, they remain imperfectly implemented and – even when significant resources are available to tackle the problem – hypertension remains a leading cause of disease burden.

Why does the problem persist? Professor Bruce Neal cites two reasons: the problem was simply so large to begin with that despite advances there remain huge challenges; and current strategies are having only limited impact.

Also, while hypertension gets a lot of attention, optimal blood pressure (BP) is likely a little lower than what is considered “normal.” Anyone with a BP above 115/70 mm Hg has increased risk – not just people with “hypertension.” There is prehypertension, defined as 120/80 mm Hg or higher, but below 140/90 mm Hg. Blood pressure 140/90 mm Hg or higher is defined as hypertension, but that does not mean that vascular damage only occurs at this high number. Evidence indicates that once blood pressure is consistently higher than optimal – 115/70 mm Hg – vascular risk increases.

Put another way, half of all disease caused by high BP occurs in people with hypertension; but that means half of all disease attributable to elevated BP occurs in people without hypertension as currently defined.

Bread and Butter Issues

Dr. Neal suggests more focus on BP and not just hypertension. Ideally, prevent BP from rising in the first place. If that’s not possible, then allocate drug therapy on the basis of risk, not just hypertension. For example, individuals with prehypertension should be treated more aggressively if they have multiple risk factors.

More broadly, he said, greater effort should be placed on population-wide environmental interventions. Recently, Dr. Neal and colleagues conducted an analysis of national salt-reduction strategies around the world.1 They identified 32 countries with such initiatives, most of which were in Europe (n=19); 26 were government-led, five led by nongovernment organizations, and one by industry. Twenty-eight countries were working with the food industry to reduce sodium levels in food and five countries had demonstrated an impact, either on population salt consumption, salt levels in foods, or consumer awareness. These strategies were led by government and were multifaceted including food reformulation, consumer awareness initiatives and labeling actions.

In his home country of Australia, there has been a national initiative to reduce sodium levels in breads both there and in New Zealand. The target in Australia is sodium 400 mg/100 g of bread and in New Zealand, the target is 450 mg/100 g. (A common basis for comparing sodium levels in food, 100 g is equivalent to about three slices of bread. Most commercial breads sold in the United States have well over 500 mg/100 g. Store brands and those often deemed the healthiest – with seeds and mixed grains – often have the highest sodium content, sometimes hitting a salt concentration higher than seawater.)

Dr. Neal’s group showed that the proportion of Australian breads meeting the national target increased from 29% in 2007 to 50% in 2010; the proportion of New Zealand breads meeting the national target increased from 49% in 2007 to 90% in 2010.

The authors suggest this information is useful in encouraging reformulating foods to lower sodium levels, which is important for health. Butter can be high in sodium, too, so many of us end up salting our salted bread when we butter it. Low sodium butter is available and not difficult to reduce in processing. That’s not always the case. A food reformulation process involves several considerations, as sodium is needed for food safety and product stability. However, given the large variations in sodium levels seen in commercial bread products, as just one example, there seems to be a broad range of acceptable (and safe) sodium content in use, suggesting reformulation to dial back sodium content can be done without sacrificing safety or taste.

References:
1. Webster JL, Dunford EK, Hawkes C, Neal BC. Salt reduction initiatives around the world. J Hypertens 2011;29:1043-50.
2. Dunford EK, Eyles H, Mhurchu CN, et al. Changes in the sodium content of bread in Australia and New Zealand between 2007 and 2010: implications for policy. Med J Aust 2011;195:346-9.

Keywords: Food Industry, Blood Pressure, Prehypertension, Risk Factors, Butter, Awareness, Food Safety, Cause of Death, Diet, Sodium-Restricted, Bread, Mortality, Premature, Taste, Hypertension

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