Roles of macros:
- Protein: structure
- Fat: Structure (lipid membranes, hormones etc.), fuel- primary fuel at rest
- Carbohydrates: Fuel- no essential dietary CHO.
Initial CHO guidelines: we need to have arbitrary high level of CHO- 65% plus
Reduced to 55% + and has now been reduced to 45%+ and this is now potentially up for review.
If the initial guidelines were correct then why have we had this shift?
The US diabetic association now has no arbitrary recommendation for CHO- dependent on the individual.
Makes sense to have individualized CHO prescription- due to some people tolerating CHO differently. We are always going to need certain amounts of fats and proteins however with CHO everything is being broken down into glucose- when the body can manufacture glucose very efficiently.
New research: Salivary amylase: the amount that people produce and how it responds to CHO. As people produce more salivary amylase, the position is that we would expect them to break down CHO more quickly and greater blood sugar level response. However what we are seeing- is the more salivary amylase people produce- the better blood glucose responses. Then potentially the people who produce more salivary amylase- the better they may be able to tolerate CHO/ may respond to it better.
People who have high AMY1 copy number variant (i.e. produce high levels of salivary amylase- are less prone to obesity). This shows people who are more tolerant to CHO are less prone to obesity.
History: closer to the equator- the more CHO people used to eat.
In hunter-gatherer societies, there was a huge variation of CHO intake from 3-50%. The anthropological evidence then therefore suggests recommendations of over 50% are too high and there needs to be a shift.
Carb-appropriate: the more activity you do the more CHO you consume (i.e. CHO intake dependent on activity levels).
How you feel is critically important: if you compare diet A to diet B- and they are exactly the same in terms of physical measurements but you feel better doing diet A. Then diet A is better.
In terms of blood sugar- having a lot of chocolate for example on a Sunday if your glycaemic control is good across the board that is not going to have much of an effect. However compared to eating pretty well but not great all of the time and your stressed you may get a blood glucose increase of 0.5mmol/mol consistently that is going to have a much greater negative effect. This is the whole chronic vs. acute idea.
Key point: There are a lot of factors in what someone’s appropriate CHO intake is, so it is a lot less cookie cutter then the advice we were given 20 year ago.
What do you look at when deciding how much CHO to prescribe someone?
· Where they are starting from- relate it to how much CHO they are currently consuming.
· How compliant they are going to be
· How tolerant someone is to CHO- you could address this by:
- Levels of bloating
-Mid afternoon slump
- GI issues (potentially from microbiome, eating CHO, eating different types of CHO, or different types of food, congenital sucrase deficiency (don't breakdown sucrose very well).
- Abdominal adiposity (combination of subcutaneous fat and visceral fat- often clear indication of metabolic disorder- you may then see insulin resistance) If someone is relatively thin on their limbs but have a large abdominal section that is quite hard and would be hard to get a skinfold- you know that this fat is surrounding the organs opposed to on the surface.
· Blood results:
-HbA1c: is something good to measure -commonly used in relation to diabetes (relates to amount of glycated haemoglobin). The higher your blood glucose over a period of time, the higher the HbA1c and the higher the risk of complications e.g. diabetes.
- High triglycerides in blood
Triglycerides are fats- why would high triglycerides in the blood suggest a high sugar intake?
High triglycerides in blood may suggest person is eating too much CHO, and too much sugar.
High CHO over time will to some degree inhibit tissue from up taking fat. Therefore if we do have the fats in the blood- then uptake may not be as efficient.
Also we get increased production of fats in the liver (de novo lipogenesis)- in response to high sugar/ CHO intake.
If we are consuming a high CHO intake- we will try and store glycogen in the muscle and in the liver, however once that capacity is saturated, it will be converted into triglycerides- for storage in liver and elsewhere.
Therefore use of the fats by active tissue is not that great as we have the preferential to use the glycogen stores if we are consuming such high CHO.
If triglycerides are distorted as well as HBA1c then we will probably see distorted cholesterol ratios- high LDL, low HDL.