Total Pageviews

Sunday, January 4, 2015

January nutritional non-sense

In this morning’s Sunday Independent magazine (Sunday, January 4th), there is a half page article entitled “Supercharge your diet” by Dr Johnny Bowden, described in the article as a weight-loss expert. I have picked out a few of his statements to comment on.
Under the heading “Protein planning”, he makes the following statement: “Many protein-rich foods – tuna, avocado, chicken- also contain the amino acid tyrosine, which leaves you feeling wide awake”. Now if you consult the USDA Food Composition Tables[1] and specifically search for tyrosine, you find that all foods that contain protein must contain tyrosine. Quite simply, proteins may vary in their level of tyrosine, but if it’s a protein, it has to have the amino acid tyrosine. Its actually hard to understand why these three foods were mentioned. For example, both cod and shellfish have more tyrosine than tuna and turkey has more tyrosine than chicken. So, if you buy into the idea that tyrosine “leaves you feeling wide awake” then any protein rich food will suffice. Now it’s worth delving into the literature to see what the true science oracle has to say about tyrosine and alertness. One study deprived subjects of sleep and subjected them to a battery of mental tests on the night the study began[2]. They would remain awake for 24 hours in total. Half were given a placebo (starch) and the other half was given tyrosine at the level of 0.15g per kg of body weight. Tyrosine improved alertness in these sleep-deprived subjects, which lasted about 3 hours. So, if you are sleep deprived for 24 hours and want to get the three hour boost from tyrosine, the equivalent dose of roasted chicken (meat only) is about 10 servings a day, each weighing 140 g. That is 1.4 kg of roast chicken and that accounts for nearly 2,400 calories. It sort of reminds me of Cool Hand Luke!

Moving on, Dr Johnny also advocates that we “Cut the carbs”. He writes thus: “Halving your carbohydrate intake will increase your vitality and energy…Carbs cause a rapid rise and fall in blood glucose, resulting in a ‘crashed’ feeling of lethargy and fatigue”. In another section entitled “Get off sugar” he writes: “The number-one drainer of energy is sugar”. I am in nutrition a long time and the concept of a “drain” is one I’m not familiar with so I can’t comment or explain on what exactly this “drain” is. So let’s think about carbs and vitality. The average person apportions their caloric expenditure as follows: 70% as basal metabolic rate accounting for the functioning of essential organs such as the heart, lungs, liver, spleen, bone marrow, brain, gut etc.; 20% as physical activity; 10% as the thermic effect of food, that is, the cost of digestion, absorption and distribution of the components of a meal. The brain alone accounts for about 20% of total daily energy use (its as high as 75% in newborns). So which tires us most, the brain or physical activity, both of which account for 20% of daily caloric intake? Now the brain is an obligate glucose consumer so it will only ever use glucose in the course of a normal day and it consumes a staggering 6 grams of glucose per hour, equivalent to 144 g/d[3]. Our National Nutrition surveys here in Ireland show that we eat 230 g/d of carbohydrate so halving that would lead to an intake of 115g/d which is only about 80% of our brain needs[4]. So my frank view of halving carbohydrate intake is that it would quite likely lead to lethargy than vitality.

Finally, I’d like to comment on the section entitled “Raw materials”. Here, Dr Johnny states that: “A lot of beneficial nutrients and enzymes found in raw foods are destroyed by high heat”. Yes, there are enzymes in plant and animal foods and because all, and I mean all enzymes are proteins, the relevant enzymes in plant and animal foods were synthesised in those foods according to the genetic code of the relevant animal or plant. These genetic codes are very different from ours and, if whole proteins that are not synthesised according to our genetic code cross our gut barrier and enter our blood system, we get an immune reaction. The immune reaction might go unnoticed or it might induce an allergy all the way up to a life threatening anaphylactic reaction. Just to be sure that this doesn’t happen we have our own enzymes in the gut, which break down the plant and animal food enzymes into their constituent amino acids. We absorb these and then re-assemble them according to our genetic code.  So, dear readers, the last thing you want to encounter is the absorption intact of animal and plant food proteins. This warning does not apply to cannibals by the way since they ingest their own species. Enough January nutrition non-sense!

[2] Neri, DF et al (1995) Aviat Space Envir Med, 66, 313-319
[3] Macdonald IA et al (2013) AJCN, 98, 633-634