Study Reviewed: Effect Of The Intake Of Lean Red-Meat From Beef-(Pirenaica Breed) Versus Lean White-Meat On Body Composition, Fatty Acids Profile And Cardiovascular Risk Indicators: A Randomized Cross-Over Study In Healthy Young Adults. Santaliestra-Pasías et al. (2022)

Collectively, proponents of these diets have adopted a three-pronged approach to address this challenge, which includes some misleading claims about how nutritional science works, how key diet guidelines came to be, and how “they” don’t want you to know that beef is actually a superfood. On the farthest fringes of these online communities, the conspiracy theories are simply delusional and unhinged, and some of the revisionist perspectives (for example, the idea that vegetable consumption is actually deleterious and detrimental to one’s health, or the idea that high LDL cholesterol is actually good for you) are laughably indefensible.

It’s a bit comical that the more conspiratorial carnivore proponents act like dietary guidelines are set in stone by large, powerful groups who unanimously share an anti-beef agenda. It’s not uncommon to hear theories about how the unscrupulous actors setting these guidelines ignore the best available evidence and intentionally skew recommendations to favor the big, plant-focused agriculture companies at the expense of the humble family farms that supply our beef. This line of thinking absolutely falls apart if you apply even a minimal level of scrutiny. Four large corporations account for around 70-85% of the US beef industry, and according to the US Department of Agriculture, “cattle production is the most important agricultural industry in the United States, consistently accounting for the largest share of total cash receipts for agricultural commodities.” According to their 2022 projections, “cattle production is forecast to represent about 17 percent of the $462 billion in total cash receipts for agricultural commodities.” They further explain that the US has the largest fed-cattle industry, and also consumes more beef than any other country. So, whether your preferred flavor of conspiracy theory vilifies large corporations or powerful governments, they’re both invested in a thriving beef industry. 

These types of conspiratorial claims completely lack face validity based on economic data alone, but more importantly, they ignore the fact that the guidelines were recently updated to walk back old guidelines limiting dietary cholesterol intake (2). In other words, one can very easily point to a recent and direct example of the US dietary guidelines getting updated in an evidence-based manner, with a change that can be viewed as more accommodating of animal-based food source consumption. I know that a big detour citing economic data is atypical for a MASS article or Research Brief, but it’s an informative anecdote that leads into a problem statement: in the online nutrition space, there’s currently a flood of content aimed at strategically altering public perception about the consumption of beef and other animal products, and the strategic nature of this effort precludes us from accepting such claims uncritically. However, terrible ideas can sometimes yield worthwhile conversations, and there are good reasons to periodically revisit dietary guidelines and to scrutinize them in an evidence-based manner. With this in mind, I wanted to briefly review a new paper that could potentially be used to promote pro-beef sentiment, and branch off into a broader discussion about dietary guidelines pertaining to meat and saturated fat consumption.

A new paper by Santaliestra-Pasías and colleagues (1) sought to compare the effects of two short-term dietary interventions: one involving the consumption of white meat (chicken), and another involving the consumption of red meat (lean beef, specifically from the Pirenaica breed of cow). In a crossover trial, 47 participants completed each dietary intervention for 8 weeks, with a 5-week washout period between interventions. I know this is a bit unconventional, but let’s start with the conclusions and work backwards to the methods. The researchers concluded that “Consumption of lean red meat (Pirenaica breed) or lean white meat (chicken) as part of the usual diet is associated with a similar response.” Based on that conclusion, I won’t be surprised if this paper starts to make the rounds by being (uncritically) shared by advocates of diets that are high in red meat and animal fats. However, while the quoted conclusion is explicitly true based on the reported findings, I question its practical utility. To explore my reasoning, let’s dig into some key methodological characteristics of the study.

When I saw the title and abstract of this study, I was really excited to dig into the pertinent details. However, the most pertinent details can’t be found, which severely limits our ability to interpret the results. First, it’s worth noting that the intervention involved college students eating prepared meals in a cafeteria setting. I thought it was a great idea to coordinate the study in collaboration with the dining hall staff; compared to the typical nutrition study that provides hot meals to participants, this seems to enable a more efficient and less resource-intensive approach. However, the researchers only provided one meal per day (lunch) during the intervention, and this only occurred three days per week. Looking through the methods, we can see that the beef meals involved a rotation of lean cuts (loin, silverside, and brisket), while the chicken meals involved relatively fatty variations (two meals included thighs and drumsticks with the skin on, while the third was a breaded and fried dish). However, we don’t have macronutrient information about the meals prepared, nor do we have data about how much the participants ate during the intervention meals. In addition, we don’t have information about what the participants ate outside of the intervention meals, which is pretty important when you consider that the intervention only influenced three meals per week. 

To be clear, I’m not suggesting that the researchers did a bad job or misreported their data – the results are thoroughly reported with a great deal of detail, and I appreciate the research team for their efforts. However, I’m simply not sure what to do with the data. I have very detailed results pertaining to a wide range of cardiometabolic parameters, but I can’t really describe the intervention that actually preceded (and presumably caused) the reported changes (or lack of changes). Nonetheless, I wanted to briefly address this study for two reasons. First, as noted previously, a lot of pro-beef folks are going to be tempted to uncritically share this study as evidence that beef has been totally vindicated when it comes to impacts on blood lipids and overall cardiometabolic health. If someone skims the abstract, they’re likely to get that impression, but there’s no way to get to that conclusion without a great deal of imagination and some very tenuous assumptions. Second, I get asked about blood lipids, saturated fat, and the health ramifications of meat intake pretty regularly, so this study opens up an opportunity to provide a quick overview of that literature. Before we get into the details, I want to remind readers that I’m not a medical doctor, a dietitian, or a blood lipid expert. I also want to remind readers, as I’ve mentioned in previous issues of MASS, that Dr. Alan Flanagan wrote a fantastic 3-part article series for Sigma Nutrition about the relationships between dietary habits, blood lipids, and cardiovascular outcomes (one, two, three), and anyone interested in a much deeper dive into these topics should consult those articles. Now, with those caveats and reminders out of the way, let’s get into it.

A pretty key element of carnivore diet misinformation revolves around muddying the waters and fabricating uncertainty about blood lipids and cardiometabolic health. I’ve seen a variety of claims, ranging from mild (LDL cholesterol is not an ideal metric for long-term risk of cardiovascular outcomes) to egregious (high LDL is actually good). Based on the best evidence available, we can confidently conclude that keeping LDL within the recommended range (<100mg/dL) is a good idea, and that having elevated LDL for a long period of time is reliably predictive of higher heart disease risk (3). However, as Alan Flanagan thoroughly explains, LDL is not the only circulating lipoprotein that is atherogenic (that is, LDL isn’t the only circulating lipoprotein that contributes to fat buildup in arterial walls and the progression of cardiovascular disease). As a result, we shouldn’t expect LDL to be perfectly predictive of cardiovascular outcomes; in fact, apolipoprotein B (ApoB) tends to be more strongly associated with cardiovascular disease outcomes, and might be a more informative blood biomarker to measure and track (4).

So, evidence indicates that the risks of high LDL and ApoB levels are cumulative in nature, and that chronically high LDL and ApoB levels aren’t ideal for long-term health of the cardiovascular system. This means that a high LDL or ApoB reading in routine screening should be a call to action for some behavioral modifications. The most basic modifications involve increasing physical activity level and reducing energy intake (5), which should lead to some degree of weight reduction. However, we can make additional dietary adjustments to proactively address elevated LDL and ApoB levels. Unfortunately, this is where things start to go off the rails – when you hop on the internet to sort out the next steps, you’ll see an abundance of perspectives with remarkably variable levels of credibility. Some people will tell you to adopt a paleo, keto, or carnivore diet, and some people will tell you to ignore your blood test result (and subsequent medical advice from your physician) entirely. Fortunately, there are some pretty simple evidence-based guidelines that one can pursue when attempting to improve blood lipids. 

I think part two of Alan Flanagan’s article series offers the most thorough description of the evidence in this area (while remaining concise and readable), but the take-home points are actually reflected quite effectively in the 2015 and 2020 versions (6) of the World Health Organization’s Healthy Diet Indicator. If you read the Research Briefs in order, you’ll recognize this diet index from another brief I published in this very same issue. It’s pretty crazy how a thorough review of the evidence and evidence-based diet guidelines tend to point in the same directions, despite all of the conspiracy theories asserting otherwise in the online nutrition space (heavy sarcasm implied). When it comes to getting blood lipids back under control, the most impactful criteria are as follows: limit saturated fat to less than 10% of total energy, try not to have a super low ratio of polyunsaturated fat to saturated fat, avoid excessive intakes of added sugars, keep processed meat to a minimum, and get plenty of fiber. The full 2015 and 2020 scoring criteria (and, by extension, guidelines) are presented in Tables 1 and 2, respectively.

Broadly speaking, these guidelines are largely compatible with a few common dietary patterns, such as the Mediterranean diet, the DASH (Dietary Approaches to Stop Hypertension) diet, and a variety of other diet patterns that emphasize lots of plant-based food sources and minimization of animal fats. These are the types of diets that just so happen to be recommended by the American Heart Association for the improvement of cardiovascular health (5).

So, what do we do with all this information about dietary patterns, blood lipids, and overall health risk? Ultimately, that depends on your perspective. With the magic of oversimplification, I’ll boil things down to three general perspectives, and address how a hypothetical person with each perspective might move forward.

Person A: “I like what I eat, and I’m not super concerned about long-term health risks.”

There’s nothing wrong with that. Obviously, no action is needed for someone with this particular perspective. The only path I’d steer this person away from is one that involves cherry-picking research to confirm their biases or preferences and spreading that information in a misleading manner. It’s totally fine to eat in a manner that contradicts evidence-based guidelines; you don’t need to spend the rest of your life trying to publicly dismantle the current guidelines and retrofit them to match your dietary preferences. 

Person B: “I like what I eat, but a routine screening of my blood lipids yielded some concerning feedback about my cardiovascular disease risk. So, I want to take action to address that.”

If I were in the shoes of Person B, my first move would be to rearrange my diet to become compliant with the guidelines in the 2015 and 2020 versions of the World Health Organization’s Healthy Diet Indicator (Tables 1 and 2). In conjunction with that effort, I’d work to reduce total energy intake while ensuring that I’m (at minimum) meeting basic recommendations for weekly physical activity levels. For some people, this might be enough to get the job done; for others, an even more selective approach to food choice might be necessary. For these individuals, it might be helpful to formally adopt one of the “named” diets recommended by the American Heart Association (Mediterranean, DASH, or a variety of well-constructed vegetarian options). Alternatively, one might wish to take a closer look at the specific saturated fat sources they’re consuming – for example, stearic acid seems to have less negative impacts on blood lipids than many other saturated fatty acids found in common foods (7). Even at this level of behavioral optimization, some individuals (particularly those with hereditary susceptibility to dyslipidemia) may still find it difficult to get their blood lipids under control; in these situations, qualified medical professionals can steer them toward additional treatment options that I’m fully unqualified to write about.

Person C: “Routine screening indicates that my blood lipids are in check, but I’d still like to take some proactive steps to minimize my long-term risk of cardiovascular disease and all-cause mortality.” 

This is a totally defensible position to take – health is multifactorial, and blood lipids only provide insight into a very narrow set of health risks. We can broadly infer that consuming large amounts of fatty, red meat has suboptimal effects on blood lipids (especially when coupled with excess energy intake and insufficient physical activity), but this falls short of a comprehensive overview of the health impacts of meat consumption. Fortunately, a recent review paper by Giromini and Givens (8) provides a great overview of the relevant literature. While a deep dive is beyond the scope of this Research Brief, the takeaways are pretty straightforward, and indicate that the health impacts of meat intake are context-dependent. First, the authors acknowledge that “when included as part of a varied diet, [red meat] provides a rich source of high biological value proteins and essential nutrients, some of which (e.g., iron) are more bioavailable than in other food sources.” For this reason, they suggest that red meat can be a valuable (but not strictly necessary) protein source for children, young women, and elderly individuals who might be at risk for select nutrient insufficiencies. However, when considering outcomes such as cancer risk, dementia risk, and all-cause mortality, health risks vary based on the type of meat in question.

As reviewed by Giromini and Givens (8), processed meats are associated with elevated health risks on a pretty consistent basis. For red meat, findings are a bit mixed, and the data look better for lean red meat when compared to fatty red meat. When it comes to white meat and fish, impacts on health typically range from neutral (negligible impact on risk) to positive (modest risk reduction). While the review by Giromini and Givens didn’t touch on egg consumption, I’d personally lump it into the “mixed evidence but probably has a pretty modest impact” category, as a variety of meta-analyses have reported conflicting findings across a broad range of health outcomes (9). If we were to rank-order animal-based food products in terms of overall health impact, this would vaguely place it somewhere between lean red meat and poultry. So, Person C might consider an approach that involves maintaining sufficient levels of physical activity, maintaining neutral energy balance at a body weight that’s compatible with their health-related goals, and maintaining compatibility with the guidelines in Tables 1 and 2. Beyond that, they might also wish to take a closer look at their food source selection in order to minimize processed meat intake, opt for leaner varieties (or smaller weekly amounts) of red meat, and err toward protein sources like fish, poultry, low-fat dairy, and a variety of plant-based sources. Again, adopting one of the diets recommended by the American Heart Association would serve as a bit of a shortcut to these food source selections, but there’s nothing inherently magical about them – they merely have a tendency to steer you toward food choices and macronutrient ratios that are compatible with the available evidence for chronic disease prevention and mortality risk reduction.

Summary

Some people like to vilify red meat, while others are increasingly acting like it’s a superfood. In reality, they’re both pretty incorrect. The available evidence suggests that it’s prudent to limit processed meat consumption, but that moderate amounts of unprocessed red meat (especially relatively lean varieties) can certainly be incorporated into a healthy eating pattern. When it comes to overall health outcomes, unprocessed meats look a lot better than processed meats, but you can make an evidence-based argument that leaning more heavily on fish, poultry, low-fat dairy, and plant-based protein sources would be preferable when compared to a diet with an abundance of red meat. Of course, red meat consumption is only one small piece of the puzzle; people interested in minimizing their risk of chronic disease or premature death should also aim to avoid overconsumption of total energy, eat plenty of fiber, minimize excess intake of added sugars, eat saturated fat in moderation, and maintain a suitable ratio of polyunsaturated to saturated fat intake. However, it’s important to note that these dietary factors are context-dependent; for someone who is physically active and maintaining negative or neutral energy balance at a body weight that’s healthy for them, there tends to be a lot more wiggle room when it comes to food selection and cardiometabolic outcomes (10). 

References

1. Santaliestra-Pasías AM, Miguel-Berges ML, Campo MM, Guerrero A, Olleta JL, Santolaria P, et al. Effect of the Intake of Lean Red-Meat from Beef-(Pirenaica Breed) versus Lean White-Meat on Body Composition, Fatty Acids Profile and Cardiovascular Risk Indicators: A Randomized Cross-Over Study in Healthy Young Adults. Nutrients. 2022 Jan;14(18):3724.
2.  Soliman GA. Dietary Cholesterol and the Lack of Evidence in Cardiovascular Disease. Nutrients. 2018 Jun 16;10(6):780.
3.  Ference BA, Yoo W, Alesh I, Mahajan N, Mirowska KK, Mewada A, et al. Effect Of Long-Term Exposure To Lower Low-Density Lipoprotein Cholesterol Beginning Early In Life On The Risk Of Coronary Heart Disease: A Mendelian Randomization Analysis. J Am Coll Cardiol. 2012 Dec 25;60(25):2631–9.
4.   Mach F, Baigent C, Catapano AL, Koskinas KC, Casula M, Badimon L, et al. 2019 ESC/EAS Guidelines For The Management Of Dyslipidaemias: Lipid Modification To Reduce Cardiovascular Risk: The Task Force For The Management Of Dyslipidaemias Of The European Society Of Cardiology (ESC) and European Atherosclerosis Society (EAS). Eur Heart J. 2020 Jan 1;41(1):111–88.
5.   Lichtenstein AH, Appel LJ, Vadiveloo M, Hu FB, Kris-Etherton PM, Rebholz CM, et al. 2021 Dietary Guidance to Improve Cardiovascular Health: A Scientific Statement From the American Heart Association. Circulation. 2021 Dec 7;144(23):e472–87.
6.   Herforth AW, Wiesmann D, Martínez-Steele E, Andrade G, Monteiro CA. Introducing a Suite of Low-Burden Diet Quality Indicators That Reflect Healthy Diet Patterns at Population Level. Curr Dev Nutr. 2020 Dec;4(12):nzaa168.
7.   Shramko VS, Polonskaya YV, Kashtanova EV, Stakhneva EM, Ragino YI. The Short Overview on the Relevance of Fatty Acids for Human Cardiovascular Disorders. Biomolecules. 2020 Aug;10(8):1127.
8.   Giromini C, Givens DI. Benefits and Risks Associated with Meat Consumption during Key Life Processes and in Relation to the Risk of Chronic Diseases. Foods. 2022 Jul 12;11(14):2063.
9.   Zhang X, Lv M, Luo X, Estill J, Wang L, Ren M, et al. Egg Consumption And Health Outcomes: A Global Evidence Mapping Based On An Overview Of Systematic Reviews. Ann Transl Med. 2020 Nov;8(21):1343.
10.   Smajis S, Gajdošík M, Pfleger L, Traussnigg S, Kienbacher C, Halilbasic E, et al. Metabolic Effects Of A Prolonged, Very-High-Dose Dietary Fructose Challenge In Healthy Subjects. Am J Clin Nutr. 2020 Feb 1;111(2):369–77.