Hypertension, defined as blood pressure of 140/90 or greater, is the leading cause of mortality and a significant cardiovascular disease risk factor worldwide, according to a 2003 report by the World Health Organization (www.who.int/cardiovascular_diseases/guidelines/hypertension_guidelines.pdf). Increasing longevity coupled with prevalence of contributing factors such as obesity, diabetes, atherosclerosis, thyroid dysfunction, dyslipidemia, inactivity, smoking, and stress only serve to highlight the importance of hypertension.
Essential or primary hypertension accounts for approximately 90–95% of the patients diagnosed with this condition, the precise etiology of which is unknown. Most hypertensives are sodium-insensitive, i.e., reducing dietary table salt does not reduce blood pressure or alter renal hemodynamics or proximal sodium reabsorption. The rest are sodium-sensitive, with compromised kidney ultrafiltration or tubular sodium reabsorption.
Secondary hypertension accounts for 5–10% of the diagnosed cases of hypertension. There are many identifiable causes, including increased cardiac output, increased vascular resistance, or both. Regardless, the course of therapy of those diagnosed with essential and secondary hypertension requires a modified lifestyle and antihypertensive medications.
Despite food industry efforts to reduce sodium in a wide range of foods, hypertension is increasing in the United States (Hajjar and Kotchen, 2003) but is more prevalent in Europe than in the U.S. (Wolf-Maier et al., 2003). Geographic differences cultural diversity, and traditions in Europe contribute to regulatory inconsistencies (Brandsma, 2006).
The United Kingdom’s Food Standards Agency recommended that consumers reduce daily salt intake from 9 g to 6 g by 2010 (www.salt.gov.uk/index.shtml) and thus cut the risk of stroke and heart attacks. This move, however, was compromised by FSA’s misleading claim that reduced salt alone was responsible for decreased blood pressure in a small clinical study. Critical examination of the study showed that other factors, including changes in lifestyle and increased consumption of fruits and vegetables, may have contributed to the apparent decrease in blood pressure.
The Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure in 2004 emphasized the use of antihypertensive medications (www.nhlbi.nih.gov/guidelines/hypertension/jnc7full.htm). However, JNC7 called for increased physical activity and increased consumption of fruits and vegetables, low-fat dairy products, and foods rich in potassium and calcium as part of a weight-reduction program. It also appeared to bend to political currents in commenting that despite the years of research discounting the clinical importance of the sodium-hypertension relationship, it may still be prudent to limit sodium intake as a prophylactic measure, even among normotensive individuals.
In the salt-hypertension debate, the failure to apply scientific rigor is startling, e.g., the failure to distinguish between systolic and diastolic hypertension, the failure to place blood pressure trends in the wider context of heart rate and fitness, and the erroneous tendency to utilize hypertension as a proxy for cardiovascular disease.
The International Food Information Council in 2005 reviewed the technological challenges associated with reducing sodium in the food supply and noted sodium’s importance in a healthy diet and its role in food preservation and the potentiation of food flavors (www.ific.org/publications/reviews/sodiumir.cfm).
The food industry’s energetic response to the apparent sodium and hypertension relationship has not decreased the prevalence of elevated blood pressure. Considering that obesity and sedentary recreation contribute to more than 90% of hypertension cases, it is time that the food industry, in collaboration with the health care community, increase efforts in consumer education in essential lifestyle modifications.
As the health care community develops therapeutic options and the food industry develops dietary opportunities to curb acute and chronic disease through functional foods, we are reminded that hypertension is not a discrete disease or clinical end point, but rather a multifaceted risk factor pitted in myth-information as a surrogate for cardiovascular disease.
by Roger Clemens, Dr.P.H.,
Special Projects Advisor, ETHorn, La Mirada, Calif.
by Peter Pressman, M.D.,
Attending Staff, Internal Medicine, Cedars-Sinai Medical Center, Los Angeles, Calif.
Brandsma, I. 2006. Reducing sodium. A European perspective. Food Technol. 60(3): 24-29.
Hajjar, I. and Kotchen, T.A. 2003. Trends in prevalence, awareness, treatment, and control of hypertension in the United States, 1988-2000. J. Am. Med. Assn. 290: 199-206.
Wolf-Maier et al. 2003. Hypertension prevalence and blood pressure levels in 6 European countries, Canada, and the United States. J. Am. Med. Assn. 289: 2363-2369.