Just Read: Dietary fat and cardiometabolic health evidence, controversies, and consensus for guidance (written by the team of non-usual collaborators…)

Dietary fat and cardiometabolic health-466
Dietary fat and cardiometabolic health-466 (View on Flickr.com)
#Food4Thought18
Forouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

This paper is part of a pretty remarkable series published by BMJ (which you can access here).

If you know the names of the people in the nutrition space, these are not names that appear on papers together usually (ever)? Their cred in this space precedes them. I’m sure many would love to be on the conference calls or emails where the piece was being formulated.

The papers are tied to a remarkable dialogue hosted by @SwissRe last week, which you can also access here.

Acknowledging that there are opposing views being published at the same time

For example, in 2017, after a review of the evidence, the American Heart Association Presidential Advisory strongly endorsed that “lowering intake of saturated fat and replacing it with unsaturated fats, especially polyunsaturated fats, will lower the incidence of CVD”.1 Three months later, the 18-country observational Prospective Rural Urban Epidemiology (PURE) Study concluded much the opposite: “Total fat and types of fat were not associated with cardiovascular disease, myocardial infarction, or cardiovascular disease mortality”.2Forouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

Physicians and human colleagues, who only want to help each other control their health and life destiny are fatigued with each piece conveniently ignoring a whole swath of literature in the references, based on who the authors are or what they say.

As if we don’t notice this is happening. Hint: we notice (see: Just Read: Cherry Picked References in Journal Articles on Diets for Health – Is there a Hidden Nutrition Curriculum for Physicians?).

This implicit and explicit obfuscation is a 20th Century style that has outlived its usefulness. Its persistence in peer-review is wacky and credibility-draining. Why not be 21st Century, it’s where we all live….

The above adds, rather than takes away credibility. Bravo.

Death (again) of the diet-heart hypothesis and the low-fat diet

This has been predicted many times over the past few years. This group making the statement makes the pronouncement undeniable for our profession, in my opinion.

Despite decades of dietary advice that the lower the total fat content, the healthier the diet, researchers and public health authorities now agree that to consider the effect of total fat intake alone on health is meaningless; different types of fats must be consideredForouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

and

Taken together, the evidence does not support a benefit of low fat diets for weight loss or prevention of overweight compared with low carbohydrate dietsForouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

I knew it when I saw it on the @SwissRe program:

This is the pronouncement I remember. December, 2016. Only 18 months later to see it here – in the span of 41 57 years, not too bad.

We should mourn all the people who were not able to enjoy metabolic health in our generation as a result. For someone who grew up in the 20th Century around a non-obese population with a dearth of diabetes, these images are now traumatic.

2018.05.30 Washington, DC Low Carbohydrate Meetup, Washington, DC USA 01-458
2018.05.30 Washington, DC Low Carbohydrate Meetup, Washington, DC USA 01-458 (View on Flickr.com)

Which Fats, Saturated or Not – More questions than answers for me

At a minimum, these findings support the safety of these dietary changes (replacing saturated fatty acids with polyunsaturated ones), although the benefits of changing the type of fat are difficult to quantify because of changes in other factors such as other aspects of diet, smoking, and emergency medical services.Forouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

To me, this is not a ringing endorsement of a swap out of one kind of fatty acid for another.

Respecting and repeating the bullet point pointed out by Twitter colleague @KevinNBass today:

Yes, and:

Both depend on assumptions about the nature of biological normality in human diets. The replacement of saturated fats with polyunsaturated fats implies that saturated fat as a nutrient causes disease and is being reduced and/or that the consumption of vegetable oils is healthy and without long term risks.Forouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

and

A point of controversy is whether such assumptions can be accepted without long term clinical trials of the kind that would be required for a pharmaceutical means of prevention. This controversy might be resolved by longer term clinical trials, but the cost and methodological and ethical challenges of such dietary trials suggest they may never be done.

It’s not that there’s resistance to saying polyunsaturates in isolation are “better” than saturated fatty acids. It’s that this discussion takes away from the bigger, more important conclusion – better to focus on taking out carbohydrates, especially processed ones, than swapping one fat for another:

In contrast, higher carbohydrate intake was non-linearly associated with increased total mortality; in nutrient substitution analyses, only the replacement of carbohydrate with polyunsaturated fats was associated with lower mortality. Although limited by the observational study design, these findings add to the concern about guidelines that focus on limiting the intake of total and saturated fats, particularly without considering the replacement nutrient.Forouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

and

Notably, these lipid markers improve—that is, triglycerides decrease or HDL cholesterol increases—when saturated, monounsaturated, or polyunsaturated fats replace carbohydrates.Forouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

This is especially true in the background of 55% of Californians with Insulin Resistance, and significant increases in fasting plasma glucose for Americans across the board.

Same with cancer.

A comprehensive review of the literature by the World Cancer Research Fund and the American Institute for Cancer Research concluded that no convincing or probable relation exists between intakes of total or saturated fat and risk of any form of cancer.Forouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

I am interested, and have fuzziness, on Omega-3 vs Omega-6. There’s not enough here for me to have a point of view. Because there is a huge credibility gap across authors in this space, we all have to read the papers ourselves and the commentary about them, as I noted in the Healthcare is Hilarious Podcast last week.

RethinkLDL

Researchers now widely recognise the existence of a range of LDL particles with different physicochemical characteristics, including size and density, and that these particles and their pathological properties are not accurately measured by the standard LDL cholesterol assay.Forouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

As I wrote previously, data from Kaiser Permanente also calls into question the validity of this single (LDL-C) biomarker: Just Read: Challenging the role of LDL vs Insulin Resistance in predicting heart disease, via Kaiser Permanente data

Real Food is the best food

Another relevant factor for weight loss is diet quality. A trial comparing diets high in carbohydrates or fats showed an equal amount of weight loss by participants when consuming whole and natural food sources while avoiding sugar, sugary drinks, refined grains, trans fats, and processed foods in general.Forouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

Low Carb Diets and Diabetes – We’re not going to get consensus from this group

This is probably the part at the end where people agreed to disagree. No worries, there will be many (many) more conferences where this will be brought up.

Here, we ourselves disagree on the significance and interpretation of these trials because long term trial evidence is not available, definitions of low carbohydrate vary substantially across studies, and few clinical trial data exist on the incidence of clinical endpoints (see related article in this series on diet and management and prevention of type 2 diabetes)

A Desire to Know – Did We Let Our Patients Down?

As I wrote in this post (Just Read: Diet: Less a Debate, More an Interest to Know What a Healthy Diet Is), I’m a family medicine specialist. Our specialty was created in the late 1960’s as answer to a lack of curiosity and patient-centeredness in medicine.

We are built to be curious, responsive, and tuned into the depth of what our patients and their communities need.

My specific generation of physicians was traumatized by the most significant ethical crisis in our profession’s history, when physicians didn’t have an answer for their patients and responded by walking out of the room.

All of those things made sure that we wouldn’t allow our patients to be let down again. This is why a statement like the below is a reminder that maybe we did let them down again.

If we let them down, what now? Are we going to stay the course or do better for the people we serve?

Feel free to check my work, to be convincing you have to be convince-able.

🙂

Citation

Components of this article are shared under the @CreativeCommons license with which it was published.

Forouhi NG, Krauss RM, Taubes G, Willett W. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ [Internet]. 2018 Jun 13;k2139. Available from: www.bmj.com/lookup/doi/10.1136/bmj.k2139

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