Proteins
1. Know the potential fates of amino acids
Amino acids, as you really should know by now, are the building blocks of proteins. Aside from simply being incorporated into proteins as they are, they can also be converted into other amino acids first. The carbon backbone that makes up amino acids can be synthesised into fat, or enter the citric acid cycle in order to generate ATP. It's pretty good that amino acids have so many different functions, because otherwise they'd just go to waste (they can't be stored).
2. Know the difference between a ketogenic and gluconeogenic amino acid
As I mentioned above, amino acids can enter the citric acid cycle. Depending on where they enter and what they end up producing, they can be classified as gluconeogenic (used to generate glucose), ketogenic (used to generate ketone bodies) or both. Leucine and lysine are only ketogenic, phenylalanine, tryptophan, tyrosine, isoleucine and threonine are ketogenic and gluconeogenic, and all other amino acids are only gluconeogenic. (Sometimes you might see the gluconeogenic amino acids classified as "glucogenic" instead.) (NOTE: I'm pretty sure that you do not need to remember which amino acids fit into which categories.)
3. Know the difference between an essential and non-essential amino acid
An essential amino acid is an amino acid that cannot be synthesised by the body and thus must be consumed in the diet. These include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threnonine, tryptophan and valine. There are also six conditionally essential amino acids which can be produced by the body, but in some cases not in adequate amounts. These include arginine, cysteine, glutamine, glycine, proline and tyrosine. Finally, there are five non-essential amino acids which can easily be produced in the body. These include alanine, aspartic acid, asparagine, glutamic acid and serine. (NOTE: Once again, I'm pretty sure that you do not need to remember which amino acids fit into which categories.)
4. Know factors defining protein quality
Protein quality is determined by two main factors: digestibility and amino acid profile. A "higher quality protein" will have higher amounts of the essential amino acids.
5. Know why protein quality of plant sources is lower than animal sources
Plant protein sources are considered to be of lower quality than animal sources as they tend to be more deficient in essential amino acids. These include lysine, sulfur amino acids (i.e. cysteine and methionine) and, to some extent, threonine.
6. Be able to describe the health outcomes associated with plant and animal proteins
Although plant sources of proteins are considered to be of lower quality than animal sources, this isn't considered to be a health issue. Vegetable protein has been found to be linked to lower blood pressure, but this could be due to a variety of other factors. As long as vegetarians and vegans take in enough calories and ensure adequate amounts of the essential amino acids, they should be fine.
Carbohydrates
1. Be able to describe the different types of carbohydrates
The main types of carbohydrates are fibres, sugars and starches. Fibres are non-digestible forms of carbohydrates, which help to provide satiety. Fibre might also help protect against cardiovascular disease, obesity and type 2 diabetes. Information on sugars and starches can be found here.
2. Know the potential fates of glucose
Glucose, which is a monosaccharide (single sugar) molecule, can be consumed directly or produced as a breakdown product of a larger sugar or starch (chain of sugars). It can be stored as glycogen in the liver or muscle, converted to body fat or oxidised to produce ATP. Glucose is the main energy source for the brain, CNS and red blood cells.
3. Know the factors defining carbohydrate quality
Carbohydrate quality can be looked at in several different ways: whole grain vs. refined grain, glycemic index and glycemic load. I'll look at these one at a time:
4. Know the difference between whole grain and refined grain
A whole grain is, well, the whole grain. A grain consists of the bran, endosperm and the germ. The bran is the "outer shell" of the seed, which contains fibre, B vitamins and trace minerals. The germ nourishes the seed, and contains antioxidants as well as E and B vitamins. Finally, the endosperm, which is the bit in the middle, essentially just contains carbohydrates and proteins. As you can see, a whole grain contains quite a few vitamins and good stuff.
A refined grain, on the other hand, only has the endosperm remaining. This gives you all the energy without any of the good stuff. Unfortunately, refined grains are a common source of starch in Western diets.
5. Be able to explain glycemic index
Glycemic index, or GI, is a measure of how quickly blood glucose levels rise after eating a particular food. A high-GI food causes blood glucose levels to rise rapidly, whereas a low-GI food causes blood glucose levels to rise more slowly. Low-GI foods are considered to be healthier, and have been associated with better outcomes for many chronic illnesses, such as diabetes. GI can be measured by giving someone a standard amount of a food and measuring their blood glucose levels over time. This is compared to a control food.
6. Know what factors affect glycemic index
Glycemic index can be affected by the type of starch, as a more branched starch with a larger surface area can be broken down more rapidly, resulting in a higher GI. For example, amylose, which is a long chain, takes longer to break down than amylopectin, which is branched. If starch molecules are trapped within the food, making them take longer to digest, this can also lower the GI. Also, soluble dietary fibre can slow the gastric emptying rate, once again slowing down the speed of digestion and lowering the GI.
7. Know the difference between glycemic index and glycemic load
Glycemic load is essentially glycemic index but corrected for the percentage of the food that actually contains carbohydrates. After all, a high-GI food might not be too much of an issue if there's only a tiny amount of carbohydrates in there. For example, a carrot has a glycemic index of 71, but a glycemic load of 4, whereas a banana has a glycemic index of 53 and a glycemic load of 21. Glycemic load can be calculated as (glycemic index * carbohydrate (g))/100.
8. Be able to explain the health consequences of carbohydrate consumption
I've already noted above that fibre can be beneficial for us. As for sugars, perhaps not so much. They are a vital source of energy, but many of us consume too much of them. This may lead to a high risk of chronic disease. Carbohydrates are not 100% good or bad per se, but you should definitely try and substitute whole grains for refined grains and limit added sugars.
9. Know the recommendation for added sugars
This is a relatively quick question to answer. The recommendation here is that no more than 10% of calories per day should be from added sugars.
This is a relatively quick question to answer. The recommendation here is that no more than 10% of calories per day should be from added sugars.
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