Red meat doesn’t kill you (and a problem with nutrition science)

This week is world iron week. I’ve talked about iron deficiency on my blog and you will be aware of the risk factors and risks associated with iron deficiency. I know, though, there are those among us who are wary of consuming one of the best sources of iron in the diet: red meat. Because, well, you know – meat kills. The most recent of these news headlines came from this study published in June of this year.

It is challenging being an advocate for eating red meat, and (in a lot of cases) encouraging clients (particularly young and not-so-young women) to eat MORE red meat, in a climate of meat avoidance. It isn’t a popular message, particularly with the bad press that red meat consumption (and production) has received over the last few years. So I thought it timely to remind you of some of the pitfalls associated with nutritional research, and why it is problematic to rely on population based research for our nutrition wisdom. This has been well covered by people much smarter than I am (read here) and relates to the above study looking at red meat and all-cause mortality.

The Nurses’ Health Study is an observational-based study – in that, it wasn’t a study that went in to try and test the effects of a certain dietary condition, instead it merely reported on what the population was doing. The food data was collected using food frequency questionnaires (FFQ), a memory based method, to determine the intake of foods spanning a four-year period. Now, if you’re reading this, you likely think more about food and what you eat than the average population. How difficult, then, would you find it answering questions related to your food intake four weeks ago, let alone four years ago? Imagine then being someone who typically doesn’t give it a second thought. A separate analysis of the data collected in this study revealed that 67% of women and 59% of men participating reported a caloric intake so low that a 70-year-old frail woman wouldn’t be able to live on, much less people who are in the prime of their lives. It has been described as ‘physiologically implausible’. Further, the caloric intake of people categorised as obese or overweight was reported as being ‘incompatible with life’. As all nutrients we eat are attached to calories, this makes all nutrient information completely unreliable.

Secondly, any of the findings are, by virtue of being an observational study, correlational in nature and not cause and effect. Given a data set large enough, enough dietary variables and a number of statistical methods at your disposal, you are likely to see significant correlations if you go looking for them. An example I saw on a blog of Chris Kresser’s was s study reporting that eating 12 hazelnuts a day increased lifespan by 12 years. Or that two slices of bacon equated to a shortened lifespan by 10 years. Yet, all headlines reporting on the study we are talking about here, and indeed the language used by study authors, suggest causality – something that cannot be determined by observation alone. Quite possibly one of the only robust findings from correlational research is that on lung cancer and smoking, where a 2000 times increase in risk of diagnosis of lung cancer was found in those who smoked. The increased risk in the study regarding red meat consumption? 10%. In most fields of science, it takes an increase in risk of at least 200% to garner interest. In nutrition, most relative risk increases are to the tune of 10-50% in either a positive or negative direction. Almost not worth writing about. Remember, too, this is relative risk. Absolute risk (when these numbers are reported) looks quite a bit different (see infographic here, a great description).

Thirdly, the prevailing message in the last 30 years is that red meat is bad for us and we should be minimising our intake of it, something that health conscious people will make a concerted effort to do. Therefore (as the research shows) those people who tend to consume the most red meat aren’t generally those that follow public health messages. They are more likely to smoke more, drink more, do less physical activity and eat less fruit and vegetables – all things which place an individual at greater health risk. While the research statistician ‘adjusts’ for these factors by way of an algorithm, it is well acknowledged that no amount of statistics will account for these unhealthy lifestyle behaviours. This is the inverse (if you like) of a ‘healthy user bias’.

And what about clinical trials looking at the harmful effects of meat? We must put it into context. A hamburger patty served with cheese and aioli, in between two slabs of bread, along with a large side of fries and a soft drink is clearly quite different to a medium rare steak with garlic butter and a side of broccolini. The overall nutrient quality and context of the diet matters whenever we are determining the healthfulness or otherwise of a food choice. Dietary patterns matter. In line with that, there is no good evidence to suggest that meat causes inflammation, and one trial in particular (out of Australia) looked at the differing effects of one 100g serving of wild game meat (Kangaroo) and the standard feedlot beef on inflammatory markers, finding no increases in inflammation after eating the Kangaroo meat. The authors suggest that the fatty acid profile of the beef (higher in proinflammatory omega 6 fatty acids) compared to the wild game meat was the potential mechanism here, but more research was required to establish this. What would be great is to see if differences existed in a clinical trial of a whole food diet that incorporated red meat, rather than there being no differentiation between sources of red meat. Grass fed meat (the majority of our meat supply in New Zealand) is higher in omega 3 fatty acids and antioxidants as a result of the way they are raised – both of which reduce inflammation.

Finally, the tri methylamine N-oxide (TMAO) story. An increase in this enzyme (generated from choline, carnitine and betaine in the gut) is associated with cardiovascular disease and there is suggestion that red meat intake is responsible for higher levels of TMAO. However, it needs to be pointed out that fish (consistently found to be a feature of healthy diets, however you look at it) raises TMAO levels well above what is found with meat. In addition, TMAO is produced in the gut, and we know how much the health of your microbiome is important for overall health. Therefore, if someone has sub-optimal gut health due in part to a poor diet, they are likely to be at increased risk of health concerns.

There is a lot to unpack and this isn’t to try to convince anyone to eat meat if they don’t want to. It is more to remind you that nutrition science is a challenging field. Regardless of assertations made by headlines, health professionals (including me!) or your next-door neighbour, studying what people eat is rife with problems and we need to take everything with a grain of salt. Which, as you probably know,  also will not (in isolation) kill you.

PC: https://www.sciencefocus.com/nature/why-do-most-cows-in-a-field-face-the-same-direction/ (interesting link BTW!)

Nigel’s diet… why so much meat?

Thanks to Nigel there was an explosion of interest in my blog post last week – and with it, a lot of questions around including certain foods in my recommendations. One I’d specifically like to address is the inclusion of animal protein (or red meat) in (what some viewed as) large amounts. Now for those who have been reading my blog for a while, this will be covering old ground as I know I’ve talked about elements of this previously. However Nigel’s documentary series has sparked much more interest in what to eat and, as the questions I got suggest, a lot of this information is new ground for many – so I’m happy to delve further into some of these issues and explain why I encourage the inclusion of red meat in the diet.

The first point to make here is that a whole-food/paleo diet (as I recommended Nigel eat) is not a meat heavy diet – it’s good to dispel that myth immediately. Sure, some doing ‘paleo’, include large amounts of meat at every meal at the expense of vegetables; however that is not what most people I know do. In fact, I eat more vegetables than some vegetarians I know. The inclusion of small amounts of meat or animal protein at each meal helps stabilise blood sugars and prevents overeating due to energy crashes. In addition, these foods contain complete proteins that are essential for the repair and rebuild of musculoskeletal tissue, they provide (amongst others) iron, zinc, iodine (fish) which are important for over 200 metabolic processes in the body important in brain, gut, liver and thyroid health, and deliver important antioxidants such as co-enzyme q 10 for heart health (and great skin!) Alongside these are the fat soluble vitamins (A, D, K) and essential fats (omega 3 fatty acids, monounsaturated fats and saturated fats) and cholesterol that form the backbone of many hormones and messenger enzymes that are responsible for delivering instructions throughout the body.

I’ve taken a broad-brush approach to the many benefits of including animal protein in the diet, but one thing I want to point out is that it’s not the eye fillet steak and the boneless, skinless, (tasteless) chicken breast that I’m talking about – the meat that is closest to the bone is the most healthy meat. Yes it’s fattier – but that’s a good thing (see above re: essential fats). There is beginning to be a trend of nose-to-tail eating now, making many of the offcuts of meat that were often binned now available to be purchased and used at the fraction of the price of an eye fillet steak (if people are willing to try them!). In New Zealand we have predominantly grass fed meat, which means we are largely protected from meat that has been grain fed. Grain fed cattle produces meat with a higher fat content but its fatty acid profile is not ideal – higher in omega 6 fats and higher intramuscular triglycerides (pro-inflammatory). The grain affects the health of the cattle, with more risk of infection and harmful bacteria which have downstream consequences to the quality of the meat we find in our food supply. While in NZ cattle are ‘finished off’ with grain, after a Twitter conversation I had the other week I believe the health consequences of this for us are negligible – though am happy to stand corrected!

And then there’s the issue of meat and cancer. And meat and heart disease. And meat and [insert health condition here that suggests you are a medium-rare steak away from certain death]. The problem with the media snippets most people are exposed to is that the finer (read: important) details are overlooked in amongst the rush to print that meat is as bad for you as smoking. Well (gasp) it’s not. Firstly, any research that suggests meat is adversely linked to any of the aforementioned conditions is association, not causational. These research studies cannot determine cause and effect and are not designed to do so. Secondly, many of the large trials asked participants to report their retrospective meat intake over a 6-10 year period once, in a questionnaire format (many people I know struggle to tell me what they ate last week). Thirdly, the distinction between actual meat and that which is found in a hamburger (for example) or even a meat sandwich in some cases is not made. There is a vast difference in quality between a rump steak and a sizzler (not to mention the latter is only around 45 percent meat and isn’t legally allowed to be called a sausage). People seldom eat a hamburger without a bun (this was before the advent of an ‘oxygen’ burger from Burger Fuel) and lumping a person who eats burgers five times per week (and upsizing with the fries and Coke) in the same category as someone who dines on eye fillet at a Pete Evan’s paleo restaurant five nights a week is problematic. Of course, I’m speculating here as to the overall diet quality of participants – but that’s all I can do as these important details pertaining to other nutrients known to affect health (i.e. processed refined carbohydrates, industrial seed oils) aren’t known. Many other lifestyle factors that contribute to poor health (such as a low level of physical activity, smoking, higher alcohol intake) are also seen in those with the highest intake of red meat and in some instances there wasn’t a linear relationship between meat intake and health (or death….) with the death rate falling in between those with the lowest intake and those with the highest intake (when split into groups according to overall consumption patterns.) These details mean little however when it comes to health reporting in the media. Nothing sells like sensationalism, and if we can draw parallels between red meat consumption and smoking then you don’t even need consumers to read the article to guarantee you’d have made an impact. Again, this is my Women’s Weekly overview; for a far more eloquent and in-depth critique of this, go to Zoe Harcombe’s review or Jamie Scott’s blog post discussing this issue.

Another big pushback against the inclusion of meat is from an ethical and sustainability perspective. Now I’m not at all suggesting that people who choose not to consume animal products based on their moral standpoint should reconsider. This is a judgement call I have no business in commenting on. However for others, thankfully the availability of free range meat now accessible at relatively cheaper cost is increasing. Demand also affects supply, and the more we ask for free range meat and eggs, the more the price will be driven down (especially considering its not essential to be choosing eye fillet for every meal). Another argument against encouraging meat consumption is that it’s not sustainable for the environment, with more demand for meat increasing the fossil fuel used to produce it, the water usage required and an increase in the methane emissions (and the carbon footprint). If we put it into perspective, most of what we do has a carbon footprint. Grain-feeding cattle may (or may not) be more resource intensive (and have a larger footprint) given what is necessary to grow the grains to be fed to the cattle as opposed to raising cows on a grass field. And promoting a vegetarian diet based on this argument is flawed given the resources required to feed the world on vegetables.

Turn your heating off a put on a jersey instead.

So that’s my stance on including animal protein (and red meat) in the diet. There are many reasons why people choose not to include red meat in their diet – but if they are based on optimising nutrient intake, protection from later chronic illness, or from a sustainability perspective, then perhaps reconsidering it wouldn’t go amiss.