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6 Points You May Misunderstand about Blood Pressure

By Paul Kriegler, RD

One-third of American adults have higher than acceptable blood pressure, and less than half of these people have their high blood pressure controlled, according to the Centers for Disease Control and Prevention.

Uncontrolled hypertension, as treatable as it is, has numerous and serious health consequences. As this CDC infographic illustrates, those with untreated high blood pressure are four times more likely to die from stroke and three times more likely to die from heart disease.

Blood pressure is a critical measure of health and reveals how much pressure is being placed on our blood vessel walls. It’s expressed in millimeters of mercury (mm Hg) for both systolic (when the heart is contracting to force blood flow through arteries) and diastolic (when the heart is relaxed and is re-filling its chambers for the next beat).

Chronically elevated blood pressure is known as a “silent killer” because it wreaks havoc on our bodies without showing obvious symptoms. Even with public awareness around blood pressure, misunderstandings are pervasive and can discourage us from seeking the full evaluation and medical assistance we may need to monitor this essential health marker. Here are six of those common misconceptions about blood pressure.

The standard method for measurement tells you all you need to know.

It’s commonly understood that standard, seated blood pressures at or near 120/80mm Hg are safest for overall health.

However, the dynamic changes in blood pressure we see in response to the body’s positional changes (e.g. standing, sitting) can provide clues about the body’s readiness to respond to stress.

Ideally, blood pressure should increase slightly upon sitting up from a laying position as well as from sitting to standing. This is supposed to happen in order to keep blood flowing sufficiently upwards against gravity to reach the brain. If blood pressure doesn’t rise slightly and you feel a bit dizzy or light-headed upon getting more vertical, it may indicate low blood volume or even more concerning signs around adrenal health and nervous system function (parasympathetic vs. sympathetic balance).

In either case, don’t just assess your overall blood pressure reading and assume stellar internal health.

Lower doesn’t always mean better.

While many people clearly understand there’s danger associated with chronically elevated blood pressure, we may be wrong to assume lower blood pressure is automatically a sign of great health.

In truth, there are concerns with hypotension, although there’s not a clear clinical definition of what number actually constitutes “low” pressure. It’s currently based on each individual’s case.

The American Heart Association isn’t too worried about “low” blood pressure unless it’s also accompanied by symptoms like dizziness, fainting, mental distractibility, fatigue, or depression (among others). In such cases (despite many of these symptoms also being related to other health concerns or even dismissed as ‘normal’), it’s important to visit your physician to assemble a clearer picture. It could be as simple as dehydration-related low blood volume or as serious as heart arrhythmias, but only your doctor can help you be sure!

Don’t assume health. Investigate it – especially if you’ve “always had low blood pressure” and don’t enjoy the vitality you’d like.

The individual numbers don’t mean much on their own.

Although this is a complicated medical question, systolic and diastolic blood pressures may predict risk of different vascular diseases. 

Some research suggests that elevated systolic blood pressure (the higher, top number) is a better predictor of bleeding incidents in the head (intracerebral hemorrhage or subarachnoid hemorrhage), while elevated diastolic pressure (the lower, bottom number) is more indicative of abdominal aortic aneurysm risk. Monitoring your numbers with this in mind can help your physician assess your health status if you’re at risk for either of these types of conditions.

Sodium doesn’t (universally) cause blood pressure to rise.

Adequate dietary sodium is necessary to maintain good health. After all, it’s a major component of our extracellular fluid (fluid outside of our cells), especially blood volume, and is also a major reason our nervous system can conduct basic signals!

Most of our dietary sodium comes in the form of salt, which is actually sodium AND chloride. The chloride is as vitally important as the sodium because it’s used in the production of hydrochloric acid that allows us to digest food and kill many of the pathogens we eat. It also allows us to make other signaling hormones such as cortisol. A lack of sodium and salt can lead to brain swelling, coma, neuromuscular deficiencies, congestive heart failure, and impaired stress response!

The Institute of Medicine recommends “healthy” adults consume 1500 mg of sodium per day to replace amounts typically lost through sweat and urination. At the same time, the USDA urges people to cap their salt intake at 2300 mg (1 tsp). The American Heart Association pushes for a stricter ceiling of less than 1500 mg per day.

Interestingly, the human body shifts into sodium-sparing mode[i] when dietary sodium intake dips below 1.5 tsp (~3300 mg) per day.

Why the differences and demonization of a substance so important to biological function? Reducing sodium intake from the typical American levels of about 3300 mg per day to between 1500-2300 mg does demonstrate reductions in blood pressure and is the main aim of the DASH diet[ii] (Dietary Approaches to Stop Hypertension). However, the effects of such a dietary plan are not so easy to pin on the sodium reduction alone.

Advising an entire population to restrict sodium may come with some risks too. Researchers found salt restriction led to poor outcomes and higher risk of premature death in those with type 2 diabetes in one study,[iii] observed immediate onset of insulin resistance (a precursor to diabetes) in another,[iv] and noted an increased risk of falls[v] in the elderly on low-salt diets.

Our bodies don’t just regulate sodium levels in isolation from other nutrients.

In fact, we aim to maintain a very tight balance between sodium and potassium in particular. Healthy kidneys can accommodate a rather wide range of sodium and potassium intake levels. The DASH diet, two-time reigning champion of the U.S. News & World Report diet face-off, all but banishes processed food (and, with it,  refined salt, sugar, and chemically altered fats) in favor of potassium-rich veggies, cold-pressed fats, and lean proteins and also ends up being lower in total carbohydrates – a dietary shift that has also been shown to result in blood pressure benefits.[vi]

Increasing potassium intake (e.g. eating loads of colorful veggies and some fruit), is a major but secondary aim of the DASH diet. The boost in potassium has also been shown to have a dose-dependent effect on countering the unfavorable effects of excess sodium intake.

The bottom line is this: if you’re moving away from processed foods towards more colorful veggies, you may not have to consciously restrict sodium. In fact, you may be able to add some! Monitor your blood pressure trends throughout this dietary change, and let you doctor know what new choices you’re making, particularly if blood pressure has been an issue in the past.

Insulin may be a major issue.

Higher blood pressures are often associated[vii] with being overweight or obese, but is the extra weight causing the increased blood pressure, or does blood pressure rise along with whatever is causing the weight gain?

The effect of obesity or excess body weight on blood pressure seems to be mediated by insulin sensitivity and/or circulating levels of insulin.

In other words, more insulin seems to raise blood pressure before actual insulin resistance is known. (Effects may wane after years of being insulin resistant.) According to many researchers, elevated insulin may play a major role in increasing blood pressure and be the main driving association[viii] between excess weight and hypertension.

Even in young adults,[ix] higher levels of fasting insulin are strongly associated with unfavorable cardiovascular disease risk factors including elevations in blood pressure. Sodium and water retention are heavily influenced by sodium-potassium balance and total insulin load. When insulin demand is high and potassium intake is low (as it is with the typical high-carbohydrate and low-activity American lifestyle), sodium and water retention are put in high gear.

Under these circumstances, the kidneys have a tough time shedding extra fluid and sodium, leading to higher blood pressure. Interestingly, when subjects replace some starchy food with monounsaturated fat[x] (such as avocados or olive products) or protein[xi] (thus, reducing total insulin demand), other cardiovascular disease indicators improve more than they do for those following standard dietary advice.

If you have blood pressure issues and you have yet to assess fasting insulin and glucose tolerance, perhaps it’s worth a look!

Conventional hypertension management can create more challenges if we’re not careful.

The latest blood pressure treatment guidelines are full of fantastic information ranging from non-pharmacologic (non-drug) interventions to extensive drug considerations for special populations. The best part is it’s all available for public viewing!

A current challenge with these first-line, non-pharmacological recommendations is that Americans are pretty bad at complying with them. Losing weight (using the DASH guidelines), limiting alcohol to one standard serving or less per day, reducing sodium intake, getting adequate dietary potassium, calcium, and magnesium (not as easy as it sounds even with apparently great nutrition habits), abstinence from nicotine, and at least 30 minutes of exercise most days is often enough to improve the body’s own ability to more safely manage blood pressure.

Apply these lifestyle changes first and faithfully, and you will significantly lower your chances of ever needing the next step.

I’d also suggest adopting good sleep hygiene and finding ways to laugh more, breathe deeply, or meditate regularly for added body and blood pressure benefits.

Oddly enough, short term administration of dark chocolate[xii] may also be a suitable non-drug strategy.

The second-line treatment for elevated blood pressure is to start pharmacologic therapy, which unfortunately is often necessary to mitigate acute threats of high blood pressure (e.g. stroke, heart attack, aneurysms to name a few).

The specific drug class or combination prescribed depends heavily on other risk factors in each individual, which commonly include obesity, insulin resistance, kidney disease or dislipidemia. Pharmaceutical drugs are known to deplete certain nutrients from our bodies and often come with side effects that need to be considered carefully for each case.

For example, an editorial in the Journal of Clinical Endocrinology and Metabolism outlines concerns that using thiazide drugs or beta blockers may increase the risk of diabetes. As a result, experts suggest those with insulin resistance/pre-diabetes risk profiles should avoid these drug classes. (At very least, the clinician should monitor both glucose levels AND insulin levels in such subjects.)

ACE inhibitors are shown to increase sodium and zinc losses. Beta-blockers disrupt Coenzyme Q10 status and may affect melatonin, while calcium channel blockers deplete phosphorus and potassium. Finally, various diuretics increase losses of calcium, magnesium, potassium, vitamins B1, B6, C, Sodium, Zinc, Folate, and CoQ10. Magnesium itself acts as a calcium channel blocker, which effectively helps blood vessels relax (which can help lower blood pressure).

As you can see, it’s more than worthwhile to commit to the first-line recommended steps before embarking on a pharmacological route with its inevitable and often significant side effects. Living a healthy lifestyle in this – as in any case – should always be our first course of action.

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[i] Michael H. Alderman, M.D., Shantha Madhavan, Dr.P.H., Wee L. Ooi, Dr.P.H., Hillel Cohen, M.P.H., Jean E. Sealey, D.Sc., and John H. Laragh, M.D. “Association of the Renin-Sodium Profile with the Risk of Myocardial Infarction in Patients with Hypertension,” N Engl J Med, 1991; 324:1098-1104.

[ii] Frank M. Sacks, M.D., Laura P. Svetkey, M.D., William M. Vollmer, Ph.D., Lawrence J. Appel, M.D., George A. Bray, M.D., David Harsha, Ph.D., Eva Obarzanek, Ph.D., Paul R. Conlin, M.D., Edgar R. Miller, M.D., Ph.D., Denise G. Simons-Morton, M.D., Ph.D., Njeri Karanja, Ph.D., Pao-Hwa Lin, Ph.D., Mikel Aickin, Ph.D., Marlene M. Most-Windhauser, Ph.D., Thomas J. Moore, M.D., Michael A. Proschan, Ph.D., and Jeffrey A. Cutler, M.D. “Effects on Blood Pressure of Reduced Dietary Sodium and the Dietary Approaches to Stop Hypertension (DASH) Diet,” N Engl J Med 2001; 344:3-10.

[iii] Elif Ekinci, Sophie Clarke, Merlin C. Thomas, John L. Moran, Karey Cheong, Richard J. Maclsaac, and George Jerums. “Dietary Salt Intake and Mortality in Patients With Type 2 Diabetes,” Diabetes Care, March 2011; 34:3 703-709; published ahead of print February 2, 2011.

[iv] Rajesh Garg, Gordon H. Williams, Shelley Hurwitz, Nancy J. Brown, Paul N. Hopkins, Gail K. Adler. “Low-salt diet increases insulin resistance in healthy subjects,” Metabolism: Clinical and Experimental, July 2011; 60;7, 965-968.

[v] Renneboog B., Musch W., Vandemergel X, Manto MU, and Decaux G. “Mild chronic hyponatremia is associated with falls, unsteadiness, and attention deficits,” Am J Med, 2006 Jan; 119(1): 71.

[vi] Appel L.J., Sacks F.M., Carey V.J., Obarzanek E., Swain J.F., Miler ER 3rd, Conlin P.R., Erlinger T.P., Rosner B.A., Laranjo N.M., Charleston J., McCarron P., Bishop L.M. “Effects of protein, monounsaturated fat, and carbohydrate intake on blood pressure and serum lipids: results of the OmniHeart randomized trial,” JAMA, 2005 Nov 16; 294 (19): 2455-64.

[vii] Haffner, S. M. Insulin and blood pressure: fact or fantasy? The Journal of Endocrinology and Metabolism, 2013: 76;3.

[viii] C.P. Lucas, J.A. Estigarribia, L.L. Darga, G.M. Reaven, “Insulin and blood pressure in obesity.” Hypertension. 1985; 7: 702-706.

[ix] Jiang X, Srinivasan SR, Bao W, Berenson GS. Association of Fasting Insulin With Blood Pressure in Young Individuals: The Bogalusa Heart Study. Arch Intern Med. 1993;153(3):323-328.

[x] Appel LJ, Sacks FM, Carey VJ, et al. Effects of Protein, Monounsaturated Fat, and Carbohydrate Intake on Blood Pressure and Serum Lipids: Results of the OmniHeart Randomized Trial. JAMA. 2005;294(19):2455-2464.

[xi] Appel LJ et al. (2005) Effects of protein, monounsaturated fat, and carbohydrate intake on blood pressure and serum lipids: results of the OmniHeart randomized trial. JAMA 294: 2455–2464.

[xii] Davide Grassi, Cristina Lippi, Stefano Necozione, Giovambattista Desideri, and Claudio Ferri,Short-term administration of dark chocolate is followed by a significant increase in insulin sensitivity and a decrease in blood pressure in healthy persons,” Am J Clin Nutr. March 2005:81 (3), 611-614.

The posts on this blog are not intended to suggest or recommend the diagnosis, treatment, cure, or prevention of any disease, nor to substitute for medical treatment, nor to be an alternative to medical advice. The use of the suggestions and recommendations on this blog post is at the choice and risk of the reader.
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