Category Archives: stroke

Does Eating Saturated Fat Lower Your Risk of Stroke and Dying?: Humility and Conscience in Nutritional Guidelines

A study presented at the European Society of Cardiology  meetings in Barcelona and simultaneously published in The Lancet earlier this month caught the attention of many of my readers. Media headlines trumpeted  “Huge New Study Casts Doubt On Conventional Wisdom About Fat And Carbs” and “Pure Shakes Up Nutritional Field: Finds High Fat Intake Beneficial.”

Since I’ve been casting as much doubt as possible on the  conventional nutritional wisdom  to cut saturated fat, they reasoned, I should be overjoyed to see such results.

What Did the PURE Study Find?

The Prospective Urban Rural Epidemiology (PURE) study, involved more than 200 investigators who collected data on more than 135000 individuals from 18 countries across five continents for over 7 years.

There were three high-income (Canada, Sweden, and United Arab Emirates), 11 middle-income (Argentina, Brazil, Chile, China, Colombia, Iran, Malaysia, occupied Palestinian territory, Poland, South Africa, and Turkey) and four low-income countries (Bangladesh, India, Pakistan, and Zimbabwe)

This was the largest prospective observational study to assess the association of nutrients (estimated by food frequency questionnaires) with cardiovascular disease and mortality in low-income and middle-income populations,

The PURE team reported that:

Higher carbohydrate intake was associated with an increased risk of total mortality but not with CV disease or CV disease mortality.

This finding meshes well with one of my oft-repeated themes here, that added sugar is the major toxin in our diet (see here and here.)

Higher fat intake was associated with lower risk of total mortality.

Each type of fat (saturated, unsaturated, mono unsaturated ) was associated with about the same lower risk of total mortality. 

 

These findings are consistent with my observations that it is becoming increasingly clear that cutting back on  fat and saturated fat as the AHA and the Dietary Guidelines for Americans have been telling you to do for 30 years is not universally helpful (see here and  here ).

When you process the fat out of dairy and eliminate meat from your diet although your LDL (“bad”) cholesterol drops a little your overall cholesterol (atherogenic lipid) profile doesn’t improve (see here).

Another paper from the PURE study shows this nicely and concluded:

Our data are at odds with current recommendations to reduce total fat and saturated fats. Reducing saturated fatty acid intake and replacing it with carbohydrate has an adverse effect on blood lipids. Substituting saturated fatty acids with unsaturated fats might improve some risk markers, but might worsen others. Simulations suggest that ApoB-to-ApoA1 ratio probably provides the best overall indication of the effect of saturated fatty acids on cardiovascular disease risk among the markers tested. Focusing on a single lipid marker such as LDL cholesterol alone does not capture the net clinical effects of nutrients on cardiovascular risk.

Further findings from PURE:

-Higher saturated fat intake was associated with a lower risk of stroke

-There was no association between total fat or saturated fat or unsaturated fat with risk of heart attack or dying from heart disease.

Given that most people still believe that saturated fat causes heart disease and are instructed by most national dietary guidelines to cut out animal and dairy fat this does indeed suggest that

Global dietary guidelines should be reconsidered …”

Amen!

Because the focus of dietary guidelines on reducing total and saturated fatty acid intake “is largely based on selective emphasis on some observation and clinical data despite the existence of several randomizesed trials and observational studies that do not support these conclusions.”

Pesky Confounding Factors

We cannot infer causality from PURE because like all obervational studies, the investigators do not have control over all the factors influencing outcomes. These confounding factors are legion in a study that is casting such a broad net across different countries with markedly different lifestyles and socioeconomic status.

The investigators did the best job they could taking into account household wealth and income, education, urban versus rural location and the effects of study centre on the outcomes.

In an accompanying editorial, Christopher E Ramsden and Anthony F Domenichiello, prominent NIH researchers,  ask:

“Is PURE less confounded by conscientiousness than observational studies done in Europe and North American countries?

 

“Conscientiousness is among the best predictors of longevity. For example, in a Japanese population, highly and moderately conscientious individuals had 54% and 50% lower mortality, respectively, compared with the least conscientious tertile.”

“Conscientious individuals exhibit numerous health-related behaviours ranging from adherence to physicians’ recommendations and medication regimens, to better sleep habits, to less alcohol and substance misuse. Importantly, conscientious individuals tend to eat more recommended foods and fewer restricted foods.Since individuals in European and North American populations have, for many decades, received in influential diet recommendations, protective associations attributed to nutrients in studies of these populations are likely confounded by numerous other healthy behaviours. Because many of the populations included in PURE are less exposed to in influential diet recommendations, the present findings are perhaps less likely to be confounded by conscientiousness.”

It is this pesky conscientiousness factor (and other unmeasured confounding variables) which limit the confidence in any conclusions we can make from observational studies.

I agree wholeheartedly with the editorial’s conclusions:

Initial PURE findings challenge conventional diet–disease tenets that are largely based on observational associations in European and North American populations, adding to the uncertainty about what constitutes a healthy diet. This uncertainty is likely to prevail until well designed randomised controlled trials are done. Until then, the best medicine for the nutrition field is a healthy dose of humility.

 

Ah, if only the field of nutrition had been injected with a healthy dose of humility and a nagging conscience thirty years ago when its experts declared confidently that high dietary fat and cholesterol consumption was the cause of heart disease.!

Current nutritional experts and the guidelines they write will  benefit from a keen awareness of the unintended consequences of recommendations which they make based on weak and insufficient evidence  because such recommendations influence the food choices  (and thereby the quality of life and the mechanisms of death) of hundreds of millions of people.

PUREly Yours,

ACP

Stroke Risk Estimation in Atrial Fibrillation: Please Give Me Lip!

The best way we have of estimating a patient’s risk of stroke if they have atrial fibrillation (AF) is by the CHA2DS2-VASc scale.

Stroke Risk EstimationThis scale take the factors we know that increase the risk of stroke and assigns 1 or 2 points. The acronym comes from the first letter of the factors that are known to increase risk as listed to the left.

Most of the factors get 1 point, but prior stroke (S) and age>75 (A) get 2 points.

We then add up your points and use another chart (or app) to calculate the risk of stroke per year.

CHA2 stroke riskYour risk of stroke is very low if you have zero risk factor; it gets progressively higher as you reach the maximum number of 9.

Treatment with an oral anticoagulant (OAC),  either warfarin, or one of the four newer anticoagulant agents (NOACS), is recommended when the risk gets above 1-2% per year.

The higher the risk, the more the benefit of these blood thinners in preventing stroke.

In lower risk patients, the bleeding risk of OAC of 1% per year may outweigh the benefits conferred by stroke reduction.

Both European and American guidelines recommend using the CHA2DS2-VASc score for initial risk stratification. The European  guideline recommends OAC therapy for males with a CHA2DS2-VASc score ≥1 and for female patients with a score ≥2., whereas the American guideline recommends use of OAC if the CHA2DS2-VASc  score is ≥2 for men and women.

I’ve been using the CHA2DS2-VASc scale for several years in my AF patients. I try to review the patient’s risk of stroke and their risk of bleeding during every office visit, and decide whether they should be on or off an OAC.

Initially, it was helpful typing all those capital letters and number twos (although I never took the time to make the twos a subscript) because it helped remind me of the factors.

However, I now view this acronym as a big pain in the neck and I am sick of typing it into my electronic medical records. It is also, really hard to say. Do you say “chad -two-D-S-two-vasc?” That is six syllables! I could have told my patient that warfarin is rat poison during that time.

And, what is with the Sc? Sex category? Why not just an S?

An Easier Term For The Stroke Risk Estimator: The Lip Score

I would like to formally request that this be termed the Lip stroke risk score in honor of Dr. GregoryLip,Greg-Cropped-110x146 Y. H. Lip who developed it at the University of Birmingham (UK).

because (per his bio): 

“The CHA2DS2-VASc and HAS-BLED scores for assessing stroke and bleeding risk, respectively were first proposed and independently validated following his research, and are now incorporated into major international management guidelines.”

birminghamIf the Lip score should somehow be unacceptable, then let’s go with the Birmingham score (recognizing, of course, that this is Birmingham, England and not Birmingham, Alabama). After all, this is what the app I use terms itself and I can type Birmingham a lot faster than CHA2DS2-VASc (even without the subscripts).

The Lip Score will be a great advance in the world of stroke risk estimation for AF patients. It will make all of us doctors creating EMR notes much more efficient, shaving precious minutes off the work day. It will be easier to communicate to patients, medical students and other medical personnel.

Finally, it gives, credit where credit is due, to Dr. Lip, who, according to his bio: “In January 2014, was ranked by Expertscape as the world’s leading expert in the understanding and treatment of AF,”

(I have no knowledge of Expertscape but you can be sure I will be investigating them soon)

Giving Lip service to stroke and atrial fibrillation,

ACP