Dietary Risks of High Intake of Fat, Salt, and Sugar (VCE SSCE Health and Human Development): Revision Notes

Dietary Risks of High Intake of Fat, Salt, and Sugar

Introduction

Understanding how dietary factors affect health is essential for VCE Health and Human Development students. This note explores three major dietary risks facing Australians: high intake of fat, salt, and sugar. Each of these dietary factors contributes significantly to Australia's health status and burden of disease through various mechanisms and health conditions.

Most Australians consume more of these nutrients than required, particularly saturated fats, sodium, and added sugars. This excessive intake contributes to increased morbidity (illness and disease rates) and mortality (death rates), reduced life expectancy, and higher disability-adjusted life years (DALY) across the population.

High intake of fat

Understanding fats and their role

Fats, also known as lipids, serve several important functions in the body. They act as a primary fuel source for energy production and are essential components of a balanced diet. However, Australians are more likely to overconsume fats rather than underconsume them, leading to detrimental health effects.

The health impact of fat consumption depends significantly on the type of fat consumed. Not all fats affect the body in the same way, which is why understanding the different categories of fats is crucial.

Types of fats

Fats can be classified into two main categories: healthier fats and unhealthy fats. This classification is based on their chemical structure and their effects on cholesterol levels and overall health.

Healthier fats include:

• Monounsaturated fats: These fats help reduce LDL cholesterol levels in the bloodstream, thereby decreasing the risk of cardiovascular disease. They are found in foods such as olive oil, avocados, and nuts.
• Polyunsaturated fats: These fats not only reduce LDL cholesterol but can also increase HDL cholesterol levels. Additionally, they help reduce blood clots and inflammation, further protecting against heart disease and stroke. Sources include fatty fish, walnuts, and seeds.

Unhealthy fats include:

• Saturated fats: These fats increase LDL cholesterol levels in the blood, raising the risk of cardiovascular disease. They are commonly found in animal products such as fatty meat, butter, and full-fat dairy products.
• Trans fats: Often considered the most harmful type of fat, trans fats not only increase LDL cholesterol but also decrease HDL cholesterol. This dual effect significantly increases the risk of heart disease and stroke. Trans fats are found in some processed foods, deep-fried foods, and commercially baked products.

High fat intake and high body mass index

One of the primary concerns with excessive fat consumption is its contribution to weight gain and high body mass index (BMI). All types of fats provide energy, and when this energy is not used by the body, it is stored as adipose tissue (body fat). Over time, consistently consuming more fat than the body needs leads to increased body weight and elevated BMI.

The impact on health status is substantial. High BMI increases both morbidity rates (illness and disease occurrence) and mortality rates (death rates) for the conditions mentioned above. This particularly affects cardiovascular disease outcomes, where excess body fat contributes to additional strain on the circulatory system.

High fat intake and cardiovascular disease

Beyond its effect on body weight, overconsumption of saturated and trans fats directly impacts cardiovascular health through their influence on blood cholesterol levels. Understanding cholesterol is essential to grasping this relationship.

Cholesterol types and their effects:

There are two main types of cholesterol that circulate in the bloodstream:

• Low-density lipoprotein (LDL): Often called 'bad' cholesterol because of its harmful effects when present in excess. LDL cholesterol tends to accumulate on the walls of blood vessels when levels are too high. This reduces the space available for blood to flow to cells and tissues.
• High-density lipoprotein (HDL): Known as 'good' cholesterol because it helps protect against heart disease. HDL cholesterol can slow down or reverse the buildup of deposits in blood vessels, reducing cardiovascular risk.

Understanding atherosclerosis:

When LDL cholesterol levels in the blood become too high, the cholesterol deposits on blood vessel walls. These deposits attract other substances, particularly calcium, which become embedded in the vessel walls. This process causes hardening and narrowing of the arteries, a condition called atherosclerosis.

How different fats affect cardiovascular risk:

Saturated and trans fats are sometimes called 'bad' fats because they increase LDL cholesterol levels, thereby increasing cardiovascular disease risk. Trans fats pose an even greater threat because they simultaneously decrease HDL cholesterol levels, removing the protective factor that might otherwise help counteract the damage.

In contrast, monounsaturated and polyunsaturated fats are considered healthier options. They actively reduce LDL cholesterol levels in the body, lowering cardiovascular disease risk. Polyunsaturated fats provide additional benefits by increasing HDL cholesterol and reducing blood clots and inflammation, offering multiple layers of protection against heart disease and stroke.

High fat intake and type 2 diabetes

Diets high in saturated and trans fats contribute to type 2 diabetes through a mechanism separate from their effect on body weight. Research has shown that these unhealthy fats can alter the composition of cell membranes throughout the body.

High fat intake and colorectal cancer

The relationship between fat intake and colorectal cancer occurs through two pathways. First, excessive fat consumption can lead to high BMI, which is itself a risk factor for colorectal cancer. However, research indicates that high intake of saturated and trans fats also appears to increase colorectal cancer risk directly.

High fat intake and the Australian Burden of Disease Study

The Australian Burden of Disease Study provides concrete evidence of how high fat intake, particularly through its effect on cholesterol levels, impacts the Australian population.

In 2015, high cholesterol was responsible for 3 per cent of Australia's total burden of disease. More strikingly, it accounted for 31 per cent of the burden specifically due to cardiovascular disease. The majority of this burden—more than 80 per cent—resulted from premature mortality rather than from living with disability, indicating that high cholesterol often leads to fatal outcomes.

Sex differences in disease burden:

Males experience a disproportionate burden from high cholesterol, accounting for approximately 67 per cent of the total burden. For coronary heart disease specifically, males experience 69.2 per cent of the burden, whilst females experience 30.8 per cent. This gender difference is less pronounced for stroke, where the burden is more evenly distributed between males (50.9 per cent) and females (49.1 per cent).

Fatal versus non-fatal burden:

Age patterns in disease burden:

Coronary heart disease accounts for the majority of DALY attributable to high cholesterol. The total number of DALY caused by high cholesterol gradually increases with age, reaching its peak in the 65-84 age group. This pattern reflects both the cumulative nature of atherosclerosis development over decades and the increased vulnerability of older age groups.

When examining DALY rates per 1000 people, the burden increases exponentially in the oldest age group (85+ years), highlighting the particularly severe impact on elderly Australians.

Summary of impacts:

High intake of salt

Understanding salt and sodium

Salt is composed primarily of sodium, an essential nutrient required for optimal human functioning. However, like fats, sodium is needed only in relatively small amounts, and excessive intake can lead to serious health problems.

In high-income countries such as Australia, processed foods represent the major source of dietary sodium for most people. This makes it challenging for individuals to control their sodium intake, as salt is often hidden in foods that do not taste particularly salty.

Extent of overconsumption:

Health consequences of high salt intake

High salt intake contributes to several serious health conditions, primarily through its effect on blood volume and blood pressure.

High salt intake and hypertension

The mechanism linking high salt intake to hypertension involves the movement of fluid in the body. When sodium levels in the body become elevated, excess fluid is drawn out of cells and into the bloodstream. This physiological response increases the total volume of blood circulating through blood vessels.

High salt intake and cardiovascular disease

High salt intake contributes to cardiovascular disease through multiple pathways, all related to the increased blood volume and hypertension described above.

When blood volume increases and hypertension develops, the heart is forced to work significantly harder to pump blood throughout the body. Over time, this additional workload can lead to heart failure, where the heart becomes unable to meet the body's circulatory demands.

The combination of increased blood pressure and potential damage to blood vessels creates a dangerous situation that significantly elevates cardiovascular disease risk. This is particularly concerning given that cardiovascular disease is already a leading cause of death and disability in Australia.

High salt intake and osteoporosis

Beyond its cardiovascular effects, excess sodium intake also impacts bone health. When sodium levels in the body are high, the kidneys respond by excreting more calcium in the urine. This represents calcium that is being removed from the body rather than being available for bone maintenance and strength.

High salt intake and the Australian Burden of Disease Study

Data from the Australian Institute of Health and Welfare and the Australian Bureau of Statistics reveal the substantial impact of high salt consumption on Australian health:

Overall burden:

Overconsumption of salt was responsible for 1.2 per cent of the total burden of disease in Australia in 2015. Whilst this percentage might seem small, it represents a significant number of preventable deaths and years lived with disability.

Prevalence of high blood pressure:

In 2017-18, approximately 23 per cent of Australian adults—equivalent to 4.3 million people—had measured high blood pressure. This figure excludes those already taking medication to manage their blood pressure, meaning the true number affected is likely even higher.

Sex differences:

High blood pressure is more common in men than in women across most age groups. Overall, 25.4 per cent of men and 20.3 per cent of women have high blood pressure. However, this pattern reverses in the oldest age group, where 45.4 per cent of women aged 75 and over have high blood pressure compared to 44.6 per cent of men in the same age range.

Age patterns:

This age-related increase reflects both the cumulative effects of dietary sodium over a lifetime and age-related changes in blood vessel structure and function. The steep rise in prevalence among older Australians underscores the importance of maintaining healthy salt intake throughout life.

Health status and burden of disease impacts:

High intake of sugar

Understanding dietary sugars

Sugars are a type of carbohydrate that occur naturally in some foods, such as fruit and honey, and are also added to many processed foods. Common sources of added sugars include confectionery, sugar-sweetened soft drinks, cordials, fruit drinks, vitamin waters, and energy and sports drinks.

Health consequences of high sugar intake

High sugar intake and high body mass index

Like fats, sugars serve as a fuel for energy production in the body. However, when sugars are consumed in amounts that exceed the body's immediate energy needs, the excess is converted and stored as adipose tissue (body fat).

Over time, consistent overconsumption of sugar leads to gradual weight gain and increased body mass index. High BMI resulting from excessive sugar intake contributes to health status and burden of disease through the same pathways as high BMI from any cause, including increased risk of cardiovascular disease, type 2 diabetes, osteoarthritis, and certain cancers.

High sugar intake and dental caries and dental disease

Beyond its effects on body weight, sugar consumption has a direct and significant impact on oral health. This relationship is particularly important for understanding morbidity patterns in children and young people.

Mechanism of dental caries:

Dental caries represents a significant contributor to morbidity among Australian children. The condition can cause pain, difficulty eating, and problems with speech development. Additionally, dental caries can impact mental health and wellbeing, particularly if the visible appearance of teeth is affected, leading to reduced self-esteem and social confidence.

Progression to periodontitis:

If dental caries is left untreated, more serious oral health conditions can develop. Periodontitis is a condition characterised by inflammation and infection of the tissues that support the teeth, including the gums and the bone that holds teeth in place. The inflammation can cause gums to recede and bone to deteriorate, eventually leading to loosening and loss of teeth.

Links to chronic disease:

These connections highlight that oral health is not isolated from overall health but is an integral component of wellbeing that influences and is influenced by other body systems.

Summary of impacts from high sugar intake

Remember!