Stroke risk is greater with both higher and lower than normal blood pressure

Posted on December 15, 2011 by Dr. Jonathan

Summary: lower than normal blood pressure results from underlying causes that need investigation and treatment. These underlying factors can increase the risk of stroke comparable to higher than normal blood pressure.

An important study recently published in the JAMA (The Journal of the American Medical Association) offers evidence that lower than normal blood pressure is a risk factor for stroke comparable to blood pressure that is higher than normal. The authors state:

“Recurrent stroke prevention guidelines suggest that larger reductions in systolic blood pressure (SBP) are positively associated with a greater reduction in the risk of recurrent stroke and define an SBP level of less than 120 mm Hg as normal. However, the association of SBP maintained at such levels with risk of vascular events after a recent ischemic stroke is unclear.”

So they set out to…

“…assess the association of maintaining low-normal vs high-normal SBP levels with risk of recurrent stroke.”

They examined two and a half years of data for 20,330 patients from 35 countries who had recently had an ischemic stroke. Patients were categorized based on their average systolic blood pressure as very low–normal (<120 mm Hg), low-normal (120-<130 mm Hg), high-normal (130-<140 mm Hg), high (140-<150 mm Hg), and very high (≥150 mm Hg). Their primary outcome measure was a stroke of any kind, and the secondary outcome was a composite of stroke, heart attack, or death from any other vascular cause. What did the data show?

“The recurrent stroke rates were 8.0% for the very low–normal SBP level group, 7.2% for the low-normal SBP group, 6.8% for the high-normal SBP group, 8.7% for the high SBP group, and 14.1% for the very high SBP group. Compared with patients in the high-normal SBP group, the risk of the primary outcome was higher for patients in the very low–normal SBP group (adjusted hazard ratio [AHR], 1.29), in the high SBP group (AHR, 1.23), and in the very high SBP group (AHR, 2.08). Compared with patients in the high-normal SBP group, the risk of secondary outcome was higher for patients in the very low–normal SBP group (AHR, 1.31), in the low-normal SBP group (AHR, 1.16), in the high SBP group (AHR, 1.24), and in the very high SBP group (AHR, 1.94).”

In other words, while the very high systolic blood pressure was the worst for both primary and secondary outcomes, the very low-normal group was the ‘runner up’ for both recurrent stroke (29%) and the secondary outcomes of heart attack or death from other vascular causes (31%). The authors conclude:

“Among patients with recent non–cardioembolic ischemic stroke, SBP levels during follow-up in the very low–normal (<120 mm Hg), high (140-<150 mm Hg), or very high (≥150 mm Hg) range were associated with increased risk of recurrent stroke.”

It’s important for both clinicians and patients to understand that lower than normal blood pressure is an indicator that things ‘under the surface’ are not working as they should. For example, autoimmune disorders that are Th1 dominant can be associated with lower adrenocortical activity due to the effect on the brain’s paraventricular nucleus—while promoting vascular inflammation.

Brazil nuts improve lipids, oxidative stress and blood vessel function in obese adolescents

Posted on November 24, 2011 by Dr. Jonathan

Summary: Brazil nuts protect against vascular disease in overweight female adolescents.

Recent research published in the journal Nutrition & Metabolism offers evidence that Brazil nuts, besides being more effective at raising serum selenium levels than selenium taken as a supplement, improve the lipid profile and protect against blood vessel damage. The authors state:

“Obesity is a chronic disease associated to an inflammatory process resulting in oxidative stress that leads to morpho-functional microvascular damage that could be improved by some dietary interventions. In this study, the intake of Brazil nuts (Bertholletia excelsa), composed of bioactive substances like selenium, α- e γ- tocopherol, folate and polyunsaturated fatty acids, have been investigated on antioxidant capacity, lipid and metabolic profiles and nutritive skin microcirculation in obese adolescents.”

Their study subjects comprising obese female adolescents were randomized to a group that consumed 15-25 g/day of Brazil nuts in capsules for 16 weeks and a placebo group. Anthropometry, metabolic-lipid profiles, oxidative stress, capillary diameters, functional capillary density, red blood cell velocity (RBCV) were measured at baseline (T0) and after the Brazil nut intervention (T1). What did the data show?

“At T1, BNG [the Brazil nut group] had increased selenium levels, RBCV and RBCVmax and reduced total (TC) and LDL-cholesterol. Compared to PG [placebo group], Brazil nuts intake reduced TC, triglycerides and LDL-ox and increased RBCV.”

In other words, compared to the placebo group, the Brazil nut cohort had better blood vessel function, lower total and LDL cholesterol and, importantly, reduced oxidized cholesterol (LDL-ox, the truly ‘bad’ cholesterol). Naturally, they also had higher selenium levels. The authors conclude:

“Brazil nuts intake improved the lipid profile and microvascular function in obese adolescents, possibly due to its high level of unsaturated fatty acids and bioactive substances.

Vitamin D status is linked to vascular health

Posted on September 19, 2011 by Dr. Jonathan

It’s become well known that an optimal level of vitamin D is important for systems throughout the body. A study just published in the Journal of the American College of Cardiology illuminates in greater detail how vitamin D is necessary for blood vessels to relax and expand properly. The authors state:

“The primary objective of this study was to elucidate mechanisms underlying the link between vitamin D status and cardiovascular disease by exploring the relationship between 25-hydroxyvitamin D (25-OH D), an established marker of vitamin D status, and vascular function in healthy adults.”

Moreover…

“Vitamin D influences endothelial and smooth muscle cell function, mediates inflammation, and modulates the renin-angiotensin-aldosterone axis. We investigated the relationship between vitamin D status and vascular function in humans, with the hypothesis that vitamin D insufficiency will be associated with increased arterial stiffness and abnormal vascular function.”

They measured serum 25-OH D in 554 subjects and assessed endothelial (blood vessel lining) function by the ability to dilate the flow of blood in the brachial artery. Microvascular function was determined by the digital reactive hyperemia index (how readily blood flows into small surface capillaries). Carotid-femoral pulse wave velocity, the radial tonometry-derived central augmentation index and the subendocardial viability ratio were used to assess arterial stiffness. Vitamin D showed effects throughout these parameters:

“…25-OH D remained independently associated with flow-mediated vasodilation, reactive hyperemia index, pulse wave velocity, augmentation index, and subendocardial viability ratio. In 42 subjects with vitamin D insufficiency, normalization of 25-OH D at 6 months was associated with increases in reactive hyperemia index and subendocardial viability ratio, and a decrease in mean arterial pressure.”

I think it is fair to assert that no cardiovascular workup is complete without measuring 25-OH vitamin D. For optimal function in most cases my preference is at least 50 ng/ml (with the usual care for rare signs of intolerance—hypercalcemia, etc.). The authors conclude:

“Vitamin D insufficiency is associated with increased arterial stiffness and endothelial dysfunction in the conductance and resistance blood vessels in humans, irrespective of traditional risk burden.”

Magnesium for inflammation and vascular dysfunction in postmenopausal women

Posted on June 21, 2010 by Dr. Jonathan

Magnesium participates in hundreds of important functions in the body, but as they authors of this study published recently in the journal Diabetes Care note:

“Although magnesium may favorably affect metabolic outcomes, few studies have investigated the role of magnesium intake in systemic inflammation and endothelial dysfunction in humans.”

The endothelium is the living lining of blood vessels, alive with functions. The authors correlated magnesium intake with plasma concentrations of high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), tumor necrosis factor-α receptor 2 (TNF-α-R2), and other markers of inflammation and endothelial function. Their data amounted to this straightforward conclusion:

“High magnesium intake is associated with lower concentrations of certain markers of systemic inflammation and endothelial dysfunction in postmenopausal women.”

Don’t forget that suboptimal magnesium levels are extremely common, become more likely with stress of various kinds (long-haul air travel for example), and magnesium excretion is increased by alcohol consumption. I have observed over thirty years that it is relatively very rare for lower extremity muscle cramps that occur at rest to not subside when magnesium status is restored. When you make the cramps go away with magnesium you’re accomplishing numerous other benefits.

Note: I have found that when the usually well tolerated bioavailable forms such as magnesium glycinate at appropriate dosages cause diarrhea, there is always a pre-existing intestinal inflammation that must be diagnosed and treated.

Walnuts improve blood vessel function in type 2 diabetes

Posted on November 5, 2009 by Dr. Jonathan

This study documents a significant improvement in blood vessel function (specifically their ability to relax and open up to allow blood to flow freely) when 56 grams of walnuts were added to the diet of the study subjects. Both the study cohort and the control group (who did not consume walnuts) were allowed to eat freely (ad libitum) otherwise. Their conclusion: “A walnut-enriched ad libitum diet improves endothelium-dependent vasodilatation in type 2 diabetics, suggesting a potential reduction in overall cardiac risk.”