Recently I have come across some very passionate dietary advisors; some have even become quite threatening. Lots of self-appointed nutrition experts have gone to great pains to describe themselves as health professionals, before dispensing some pretty emphatic positions on the cause and effect of diet-induced maladies in humans. Unfortunately, ever ready to hold people who advise the public on their health to a higher standard – I usually insist on some actual evidence. Sometimes this is followed by snarling and gnashing of teeth, other times a kind of stunned silence; more than once I’ve got the impression the person I was talking to didn’t understand the question. I digress. I love evidence. I am committed to evidence. I always consciously let the evidence inform my opinion, rather than the other way around.
So in that spirit; and at the risk of being accused of being a cherry-picking, good-for-nothing, data-mining so-and-so; I thought I’d share a few pearls of conventional dietary wisdom about cause and effect in human nutrition, and throw in a good old-fashioned peer-reviewed published clinical study for good measure. I mean I love the smell of a good hypothesis in the morning….
Saturated Fat Consumption is Associated with Cardiovascular Disease.
It seems almost intuitive. Eat too much yucky fat equals too much fat on our tummies equals too much fat in our arteries equals we die a miserable but preventable death. But here’s the thing: intuition isn’t science! The American Journal of Clinical Nutrition published the results of a meta-analysis (that’s lots of other very good studies put together so we get a big sample size) of 347,747 people over a 5-23 year period and found no significant evidence for concluding saturated fat consumption increased the risk of coronary heart disease or cardiovascular disease. In other words, those that ate saturated fat did not succumb to cardiovascular or coronary heart disease any more than any other group in the population. Read it yourself “ajcn.nutrition.org/content/early/2010/01/13/ajcn.2009.27725.full.pdf+html”
So is saturated fat bad for your heart health? The truth? We just don’t know. But right now it looks unlikely. Few topics have been research as extensively. That’s the truth. So why do nutritional health professionals preach it as gospel? I mean even the Heart and Stroke Foundation’s open letter response to Tim Noakes writes “While studies are unclear about the effect of saturated fats on health, ….” before going on to suggest saturated fat should be replaced by unsaturated fat. What are they trying to say? “We advise you to replace saturated fat with unsaturated fat, but we’re just not sure why?” Ok, then why don’t they just say that? Why should the public be left to figure out their cryptic sentences and double-speak? Remember: A higher standard. Cut and paste “health24.com/Medical/Heart/Foods-diet-and-your-heart/Heart-Foundations-open-letter-to-Tim-Noakes-2013021” to see for yourself. As for their undisguised attempt to obfuscate the issue by making an irrelevant reference to trans-fats in that letter simply highlights the flimsiness of their response.
Eating lots of little meals during the day helps you lose weight
Don’t get me wrong, I love eating. But two studies in the British Journal of Nutrition (1997, 2010) found no evidence of a relationship between meal frequency and weight loss. Again, I wonder why ‘nutritional experts’ (lots down at the gym) keep repeating this nonsense. Read the studies “ncbi.nlm.nih.gov/pubmed/19943985” and “ncbi.nlm.nih.gov/pubmed/9155494”.
Again this is personal opinion being dressed up as nutritional fact; no different to telling a child that eating cheese at night will give them bad dreams. It’s nonsense; and do you really want to be the kind of ‘health professional’ that presents nonsense to gullible clients? Remember when everyone got grumpy because their kid’s polony had horse meat in it? If you going to sell something make sure it contains what it says it does – health advice is no different.
Calories in must be less than Calories Out if you want to lose weight.
Assume we could give the same person 2,500 calories a day. One test we’ll give them 60% of their energy in the form of carbs; in the other we’ll limit that to 20%. Who will lose more weight over a year? Remember when you cut fat, you invariably increase carbs; and vice versa. I wish dieticians would consider that next time they advise diabetics to follow a ‘low-fat slimming diet’. So who would lose more? Well, in another well designed meta-analysis published in The New England Journal of Medicine (2008) compared a calorie restricted low-fat and a calorie restricted Mediterranean diet against an unrestricted calorie low-carb diet (Atkins). Firstly, why the need to restrict low-fat and Med calories I wonder? Anyway, long story short, Mediterranean and Atkins came out top. Both beating low-fat at every interval measured during two years.
Now….me wonders about this calorie in/calorie out – whole energy balance thing. The low-fat and Med dieters were restricted to 1800 calories a day (men) and 1500 calories a day (women). The study was well designed, with high adherence rates and confounding variables seemingly well controlled – yet the Med diet beat the low-fat by a significant margin. But how can that be? If the law of thermodynamics applies, and the “calories in must equal less than calories out” dogma holds, then surely after two years both groups would have lost the same? Any other result would shake the very foundation of the conventionally trained dietary establishment. I mean what happens to the bog-standard mantra … “To lose excess weight you must eat less calories, do more exercise in order to consciously create a negative energy balance”. Read the study for yourself “nejm.org/doi/full/10.1056/NEJMoa0708681#t” the you decide whether this calorie, energy balance thing makes any sense. The data doesn’t support the hypothesis – and usually when that happens we reject the idea. Yet for some reason, the nutritional establishment are hell bent on holding onto this notion as if it were some immutable truth. It isn’t. There’s still a lot of research required.
Seems there’s a little more to this nutrition mystery than meets the eye. And while I picked a few very well designed studies published in some of the most reputable journals to illustrate just how little we actually know about cause and effect in human nutrition; I hope I’ve made a few more people little more sceptical of all this 'dietary advice' floating around.