After dramatic improvements in my son, I was inundated with queries from people wanting to try the Royal Prince Alfred Hospital exclusion diet for a range of symptoms. While I was pleased to help, I was concerned I did not have the required expertise to assist. I therefore studied for a Graduate Diploma of Human Nutrition, completed in 1991 through Deakin University. My course covered biochemistry, food science, general nutrition, nutrition across age groups; food, health and non-communicable diseases; and dietary guidelines. I completed a research project in asthma and food sensitivities in adults, and an in-depth literature review on food sensitivities in young children. I will write more on my food sensitivities research in future posts. For the purposes of this series of posts on my own food history, I have summarised key general nutrition points I took on board for myself or my family, as how I perceived things at the time. Research and my ideas on some of these issues has moved on since the early 1990s. In time, I will expand on each of the below, updated to the current time.
Summary of some key areas learned:
- Lipid Hypothesis: the concept of high cholesterol levels in the blood, and especially high levels of Low Density Lipoprotein [LDL] fraction, increases risk of fatty plaque build-up in arteries, seen as a higher risk of heart disease. High Density lipoprotein (HDL) cholesterol is/was considered protective, depicted as a scavenger returning cholesterol to the liver. Triglycerides (TG) are also seen as a risk in heart disease.
LDL was thus depicted as ‘bad’ cholesterol and HDL as ‘good’ cholesterol, although the good/bad terms are simplistic and not technically correct. The ratio between the two and TG levels are now considered more appropriate markers.
- Diet-Heart Hypothesis: Fatty foods contain mixtures of different fatty acids, broadly summarised into saturated fatty acids (SFA), polyunsaturated fatty acids (PUFA) and mono-unsaturated fatty acids (MUFA). It is considered that SFA increase LDL levels and raise the risk of heart disease, PUFA lowers both LDL and HDL; whereas MUFA lowers LDL and not HDL. In the 1960s when my father had his heart attack, PUFA were recommended and MUFA were seen as ‘neutral’. Research in the 1990s began moving away from recommending PUFA (such as safflower and sunflower oils) to MUFA (such as olive and canola oils). MUFA were seen to lower LDL cholesterol while maintaining protective HDL levels.
- Energy: ‘Energy’ in a nutritional sense is measured by calories or kilojoules. A food can be measured by its energy density (kilojoules per 100 gram) and/ or nutrient density (micronutrients). Energy balance is when energy in as food equals energy out from metabolism, activity, thermic effect of eating, or growth (in babies, children and pregnant/lactating women). Chief sources of food energy are mainly carbohydrates and fats; and protein to a moderate extent. When food is unavailable the body uses its stores of carbohydrate (glycogen) and fat (adipose tissue). Body protein (eg from muscles) can be used as an emergency fuel. Glycogen holds water and initial weight loss on a diet tends to be predominantly water loss as the body depletes its glycogen stores. Fat loss, not weight loss, should be the aim in any weight-loss diets.
- Protein: Proteins are complex structures comprised of long chains of amino acids. There are 20 amino acids required as the building blocks of body proteins and 8 of these (9 in infants) are essential and must be obtained from the diet. Animal foods such as egg, meat, fish and poultry generally provide all essential amino acids in correct ratios and adequate quantity per kilojoule of energy provided. Plant proteins are said to limiting in one or more essential amino acids. However, if one or more foods with different limiting amino acids are eaten at the same meal (such as eating beans with rice) they ‘compliment’ each other and provide all essential amino acids in the correct ratio. (This concept is now considered out-dated. It is not necessary to eat foods with complementary amino acids at the same meal as long as adequate protein and calories are eaten over the course of a day.)
- Glycaemic index: Early research on the glycaemic index showed foods with carbohydrates varied greatly in their triggering of a rise in blood glucose after the same amount of carbohydrate in a food. Refined foods such as bread and white rice trigger immediate and large rises in blood glucose (hyperglycaemia), and rebound hypoglycaemic effects several hours later, where one can feel hungry. In contrast, foods such as oats, beans and lentils have a slower rise, a lower peak response and a more sustained effect, thereby providing greater satiety (fullness) after meals and feeling less hungry hours later.
- Fibre can be broadly divided into soluble and insoluble fibre with different properties. In summary, insoluble fibre (in wheat and other cereals) absorbs water , swells and speeds the content of food through the gut. Soluble fibre (in oats, legumes, fruits and vegetables) forms a gel, slows food absorption. Some soluble fibre have also shown to have cholesterol lowering benefits.
- Iron: Haem sources of iron in foods such as in meat is a more bio-available form. Ascorbic acid (Vitamin C) consumed at the same meal helps absorption of non-haem iron sources such as iron in cereals and vegetables, hence the concept of consuming fruit juice (containing Vitamin C) with wholegrains or fortified breakfast cereals. Despite diets with meat, fruit, vegetables, wholegrains or fortified cereals; some people, women in particular, cannot obtain adequate iron from food and may require supplements.
That is some of the biochemistry and food theories I had learned.
How I applied these to my own diet is the subject of my next post.
This is a series of posts on my food history from my childhood up until 2013.
My food history # 1 – My childhood diet – Late 1950s, early 1960s
My food history # 2 – Mid 1960s – First nutrition lessons
My food history # 3 – Late 1960s – Times are a-changing
My food history # 4 – Critical moments – my father
My food history # 5 – Fit 1970s – fibre – fruit – free of sugar
My food history # 6 – 1980s – Critical moments – a health scare – hypertension
My food history # 7 (part 1) – 1980s – Food Sensitivities – shattered ideals of healthy food
My food history # 7 (part 2) – 1980s – Food sensitivities – proving the culprit foods
My food history # 7 (part 3) – 1980s – Food sensitivities – hypertension & biogenic amines
My food history # 8 – The 1980s Healthy Eating Pyramid
My food history # 9 – The 1990s Nutrition studies – low GI – lipoproteins
My food history # 10 – 1990s combining ‘friendly’ with ‘healthy’ – a bland yet healthy diet
My food history # 11 – The 2000s – slow ticking time bombs
My food history # 12 – Critical events and life catastrophes
Disclaimer: Nothing in this article or on this website should be taken as medical or dietary advice. Anyone reading any information provided within should seek advice from their own medical practitioner for any issue, disease, illness or health-related problem they may have. Always seek your own advice from a medical practitioner or dietitian before changing your own diet.