Sunday, July 21, 2013

Why We Should Question Dietary Advice: Part 3

Choline

Eggs and organ meats have been demonised in the past due to their high cholesterol content.  Some, but not all, dietary recommendations now don’t recommend against dietary cholesterol and do recommend a small number of eggs.  Eggs and organ meats are two of the few reliable sources of choline in the diet. 

Humans seem to have a large requirement for choline.  The adequate intake (AI) comes largely from this study which found that 500mg of choline was sufficient to prevent an increase in liver enzymes in plasma (which is a of signal liver damage) in healthy adults [1].  So add 10%, use body mass to adjust for women, and you’ve got your AI [2].  Seeing as 500mg was simply sufficient to prevent liver damage it’s debatable whether 550/425mg is enough for good health. 

Regardless of whether we should be eating more than 550/425mg of choline daily or not, it doesn’t change how hopelessly deficient in choline current dietary recommendations are.  The Mediterranean diet and the DASH diet, which are very similar to what the dietary guidelines recommend, only provide 55% and 46% of the choline requirement for men* [3].  To meet the requirement these diets would need to include an average of 2 eggs or 50-100g of liver daily.  As expected, in the real world most people are choline deficient [4] [5]

* Sometimes in the USDA database choline and other nutrients aren’t measured.  This study did also use World’s Healthiest Foods database, but even so the choline numbers will probably be slightly higher 

Severe Reductionism and Inappropriate Classification

The dietary guidelines (and poorer quality sources of dietary advice in particular) have a habit on reducing entire food groups to a few nutrients.  Little attention is given to the nutrients not on this list 

The Sum of Nutrients In Dietary Advice
Good Nutrients:
  • Protein 
  • Complex Carbohydrates
  • Fibre 
  • Calcium 
  • Iron
  • Zinc 
  • ‘Antioxidants/Phytochemicals’
Bad Nutrients:
  • Fat (sometimes) 
  • Saturated Fat 
  • Sugar (sometimes)
  • Salt

I think to a large extent they are fighting the wrong battles.  But anyway, what this also means it that if you reduce a food group to one or a few nutrients then anything with those nutrients is considered an ‘alternative’ regardless of the often large differences in the rest of the nutrient profile.  For example the dietary guidelines reduces dairy foods to calcium so anything high in calcium, like calcium fortified, soy imitations of dairy foods are considered a dairy alternative (see Dairy and Alternatives) and they reduce meat to protein so anything high in protein like legumes are considered a meat alternative (see Meat, Eggs and Alternatives)*.  This is despite dairy and meat being far better sources of their ‘key’ nutrient (bioavailability, etc) and having a very different nutrient profile to their plant-based ‘alternatives’ 

* The 2011 draft for the Australian dietary guidelines described nuts and seeds as being protein rich even though almost all nuts and seeds contain less than 15% of their total calories as protein. 

** Another form of reductionism is the frequent grouping and classification of SFA and artificial TFA as ‘bad fats’ simply because they both increase LDL-C 

‘Nutrient Density’

Dr Joel Fuhrman developed the ANDI system for nutrient density which excludes some essential nutrients (some vitamins and minerals, DHA, etc) and includes some non-essential nutrients (like phytochemicals).  The net result is that under this ranking system fruits and vegetables perform well and animal foods perform badly [6]. 

The Australian dietary guidelines (no doubt others) do the same thing although to a lesser extent.  They don’t define nutrient density and they don’t deliberately ignore certain micronutrients, but what they do is reduce food groups to a few nutrients and discuss non-essential nutrients found in plants such as fibre and phytochemicals but not the non-essential nutrients found in animal foods such as carnitine, carnosine, creatine, taurine and coenzyme Q10*.  Check the links for research related to them.  I’m far more excited about the potential of them in clinical trials than I am with fibre and phytochemicals. 

See the table in Meat, Eggs and Alternatives for a general sense or which nutrients plant and animal foods tend to be rich in.  From our perspective as omnivores the even distribution should hardly be surprising.

* Some plant foods are good sources of CoQ10 too [7] 

** I recently listened to this debate between Dr Eric Westman and Dr T Colin Campbell.  At one point Colin Campbell said meat has no antioxidants.  It’s sad really, for all his titles and letters, he isn’t even aware of carnitine, carnosine, creatine, taurine or CoQ10 (probably others too). 

Further Reading:
(1) Meeting the Choline Requirement -- Eggs, Organs, and the Wheat Paradox

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