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.

Shift work and health: the Cliff notes.

I’ve worked in a wide variety of jobs in my life. Like many people, I spent the latter part of my high school and university years cleaning toilets, clearing tables, washing dishes, delivering pizza and making sandwiches when there was only one sandwich maker in town. Subway, George St. Aaah….the memories. Somehow I was always put on the graveyard shifts of Thursday night 8pm-4am and Saturday 10pm-6am. Though it totally went against my natural tendency to be early to bed, early to rise, they were the most fun shifts to work. As one of the few places open 24 hours over the weekend, we got queues out the door of students either rolling in from the Cook or stumbling home from KCs, with the busiest period being from 2.30am to around 4am. I still remember the excitement at serving both a glazed eyed Marc Ellis and Rachel’s brother Jonathan from Shortland Street – before seeing Shorty stars was as ho-hum as …. seeing Shorty stars. Anyway. I’d get home either 4.30 or 6.30 and sleep 5ish hours before getting up and try to get back into a daytime routine. I always felt rubbish through lack of sleep and so thankful that I wasn’t pursuing a career that required me to do shift work.

Now, though, amongst the industries that have always needed to be available 24/7, the global society we live in now necessitates other occupations to put in hours that extend beyond the 9-5. The prevalence of employees working shifts in the media, healthcare industry, on the front line and in the corporate world is estimated to be around 20% and the available data in New Zealand is in line with this. This is a large subsection of the working population, and why it’s of note is that there are well established links between shift work and poorer health outcomes – both short and long term. The constant sleep deprivation that results from shift work is a major underlying issue.

The most important things we can do to help mitigate the effects of chronic sleep deprivation that occurs due to shift work (aside from actually sleeping!) are the very things that go out the window. A regular exercise routine is more difficult to maintain, due to tiredness from lack of sleep or the inability to structure if you are on a shift cycle that changes from day to night. Eating healthily is more difficult as having motivation to plan and prepare is more challenging, and often the pull to higher sugar, poorer nutrient foods is governed by cravings and accessibility. In addition, perhaps overlooked, maintaining relationships can be more difficult as the non-sociable hours of shift work impact on our availability to spend time with friends and family. Hanging out with John on the 5th floor is not the same.

It’s also well established that the affects on circadian rhythm put shift workers at a higher risk of many chronic diseases. Up until 150 years ago we were constrained by the natural sunrise and sunset and life on earth had evolved according to this. When artificial light was invented there were suddenly more hours in the day that could be spent being awake, and the shift in our wake and sleep cycle impacts on metabolism, hormones, digestion, cardiovascular system; in fact all of our cells in our body is affected by this. Sleep deprivation in the short term increases insulin resistance – it takes just a single nights’ sleep for this to occur. There is an increase in the risk of injuries on the job, and a link between both acute and chronic gastrointestinal problemsMood disorders are also associated with circadian rhythm disruption, and both observational and experimental data point to an increased risk of obesity in shift workers due to these circadian rhythm changes.  Over the long term, there is an increased prevalence of risk factors associated with the metabolic syndrome, type 2 diabetes, cardiovascular disease and cancer are all seen in shift workers compared to those who keep a more normal work schedule.

While you might think people who are early risers would be more negatively affected by shift work, this hasn’t been found to be the case.  Research shows that those who are late risers have lower levels of melatonin (a hormone that mediates the sleep-wake cycle); the suppression of which is one proposed mechanism for the increased health risks associated with working hours that disrupt circadian rhythm.

So what to do? Obviously, being able to opt out of shift work is not realistic for the 20% of the population who live and work in this 24 hour society. This report details the interventions in the research setting that have been found to be most beneficial. These include scheduling shifts to be ‘forward’ shifts rather than backward shifts (i.e. moving from a morning, to an afternoon, to an evening shift), avoiding stimulants such as coffee (in excess) and wearing light blocking eyeglasses on the way home from night shift. Sleeping in a dark room and wearing an eye mask will also help.

Along with the above, ensuring good sleep hygiene practices through both diet and exercise are essential. Though it might be the last thing you feel like doing if you’re just getting into exercise, a routine that you stick to will go a long way to helping you mitigate these effects. Exercise is so important for everyday health and well being, that to ignore it would only further exacerbate some of the health issues mentioned above. Further, in the face of sleep deprivation and acute insulin resistance, strength training helps improve insulin sensitivity and may minimise the blood sugar disruptions experienced. As mentioned, coffee is likely one of the first things you go to when you feel like you need an energy hit, but instead of this, why not try green tea – it has L-threanine in it which helps keep you alert without the caffeine hit. Perhaps save coffee for your days off (and limit to just one); dare I say it – try a decaffeinated brand otherwise. Some companies like to supply food for their employees, and this tends to be cheap plain biscuits, white bread and jam, and other types of food to provide a quick hit of energy when time is of the essence and there is no time to stop for a real meal. These options, along with the vending machine, are the last foods you want to be eating. On your off days make it a habit to prepare two or three ‘dinner’ like meals that you can freeze and eat throughout the week. Trying to structure your whole food, minimally processed meals so they are ‘dinner’ like at dinner time (before you head into a night shift, perhaps), lunch like in the middle of your shift, and then a lighter meal before you hit the sack in the morning will maintain the regularity of meals regardless of whether you’re working or not. Being prepared with your good food options means you can avoid those that are available at work. In addition, a magnesium supplement (with an amino acid or citric acid chelate) before bed can help promote good sleep. Finally, if you are constantly waking up, practicing some deep breathing in bed can help calm you down and send you back to sleep. Diaphragmatic breathing will decrease your sympathetic nervous response – ‘fight or flight’ and the levels of stress hormones entering the bloodstream which are released because of this which could prevent you falling easily back to sleep.

Shift work is a necessity for many people, and some fare better than others. If you are a shift worker who fares fairly well despite the disruption in sleep and subsequent poor lifestyle habits you may not feel that these tips would apply to you. However maintaining your health is as important now to offset the long term effects of shift work.