Sometimes I notice when coming onto the assessment unit there is a smell which is a combination of stale urine/bowel gas and air freshener. But when I started at 8 this morning everything is overpowered by the wonderful scent of fresh toast. The domestics are pushing trolleys on which is piled not only toast, but also cornflakes and porridge (that’s oatmeal for US readers), jam and cups of tea.
I like seeing patients first thing in the morning, because if they have eaten and kept down their breakfast they are not likely to be too unwell – and there’s a good chance they will be able to go home.
This morning my first patient was Brian, a 57 year old man who has type 1 diabetes and was admitted from clinic with an infected foot ulcer. He had eaten his breakfast. His diabetes specialist was concerned about osteomyelitis (infection in the underlying bone) and wanted him to have an MRI scan and intravenous antibiotics.
Brian has had diabetes since the age of 10, and has poor eyesight due to diabetic retinopathy, and poor kidney function due to diabetic nephropathy. Both are caused by damage to small blood vessels from diabetes.
The first question I asked the young doctor who was with me was the obvious one:
“Why does toast go brown when it is cooked?”
She looked at me in a slightly worried but kindly way, not sure how to respond – she had only been working on the unit for a week or so and was keen to give a good impression.
The answer is that the glucose molecules, which make up starch combine chemically, when heated, to wheat protein – something called a Maillard reaction, to produce a brown carbohydrate/protein complex. The chemistry is complicated, but this reaction is vital to producing all sorts of wonderful foodstuffs (apart from toast), including the really tasty brown, crispy coating on cooked meat, the main taste of gravy, soy sauce, Worcester sauce, the tasty bits on the surface of fries and, indeed, the brown surface of cornflakes which gives them a taste of more than plain wheat flakes.
You may be interested to know that there is an International Maillard Reaction Society – http://www.imars.org/online/
I can imagine that when delegates go to meetings they might dress up as Louis Camille Maillard –
Also there is probably some caramelization of the starch glucose molecules. When heated sugars alone will form polymers which are brown-coloured tasty caramels and are used for all sorts of purposes such as food colouring (eg. the brown in cola).
So how does this relate to Brian’s diabetes?
Well, the reason that his blood vessels are damaged by diabetes is because, just like in the toast, high levels of blood glucose (which is the main problem in diabetes) combine with protein in blood vessels. In particular glucose undergoes the same Maillard reaction with the amino acid lysine which has an amine group sticking out.
The formation of the glucose/protein complex is not easily reversible and causes permanent damage to blood vessel function, resulting in eye, kidney, skin, heart, brain and a whole lot of other problems for diabetics.
The result of the Maillard reaction between sugar and lysine creates what are known as advanced glycation end-products (AGEs). There is now a huge literature about AGEs and AGE receptors called RAGEs. Many think AGEs are also important in aging and dementia, and there is evidence that RAGEs may be either a protective or more damaging. A good review about AGEs and diabetic vascular injury is:
This is my first ever post and I would love to have feedback.
Disclaimer: Patients described in this blog are not real, but typical of those we see in our hospital