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Diet, health and the burden of disease

Watch Professor Alex Johnstone discuss how diet impacts health and the burden of disease.
SPEAKER 1: A healthy diet is a diet that helps to maintain or improve overall health because it provides the body with essential nutrition to include fluid, macro-nutrients, micro-nutrients, and adequate calories. Various nutrition guides are published by medical and governmental institutions to educate individuals on what they should be eating to be healthy. This means eating a wide variety of foods in the right proportions and consuming the right amount of food and drink to achieve and maintain a healthy body weight.
The World Health Organisation recommends including to ensure that foods chosen have sufficient vitamins and certain minerals and to avoid directly poisonous, such as heavy metals or a carcinogenics, such as benzene substances, avoiding foods contaminated by human pathogens such as, E coli or tapeworm eggs, and replacing saturated fats with polyunsaturated fats in the diet to reduce the risk of coronary artery disease and diabetes. It’s not just diet that has an influence on disease risk. Other risk factors such as a person’s background, lifestyle, and environment are known to increase the likelihood of certain non-communicable diseases. A non-communicable disease is a medical condition or disease that is not caused by infectious agents so it is said to be non-infectious or non transmittable.
Non-communicable diseases can refer to chronic diseases which last for long periods of time and progress slowly. Most non-communicable diseases are considered preventable because they are caused by modifiable risk factors. Whilst we can’t change our age, gender, genetics, we can alter our exposure to air pollution and other behaviours, such as smoking, an unhealthy diet, and physical activity; which can lead to hypertension, which is high blood pressure, and obesity. In turn, leading to increased risk of many non-communicable diseases. The World Health Organisation has identified five important risk factors which are; raised blood pressure, raised cholesterol, tobacco use, alcohol consumption, and being overweight or obese.
The other factors associated with a higher risk of non-communicable diseases include a person’s economic and social conditions, also known as social determinants of health. It has been estimated, if the primary risk factors were eliminated, 80% of cases of heart disease, stroke, and type 2 diabetes, and also 40% of cancers could be prevented. Interventions targeting the main risk factors could have a significant impact on reducing the burden of disease worldwide. Efforts focused on better diet and increased physical activity have been shown to control the prevalence of non-communicable diseases. The World Health Organisation makes the following five nutrition recommendations with respect to both populations and individuals.
Number one, maintaining a healthy weight by eating roughly the same number of calories that your body requires. Two, limit intake of fats. No more than 30% of total calories should come from fats. Prefer to intake unsaturated fats to saturated fats and to avoid trans fats. Three, eat at least 400 grammes of fruit and vegetables per day. Potatoes, sweet potatoes, cassava, and other starchy roots do not count. A healthy diet also contains legumes, such as lentils and beans, whole grains, and nuts. Four, limit the intake of simple sugars to less than 10% of calorie intake, or 25 grammes a day is even better. Five, limit salt or sodium intake from all sources and ensure that the salt is iodized.
Less than 5 grammes per salt per day can reduce the risk of cardiovascular disease. Let’s explore how we would implement these in a couple of nutrition examples. So the risk of heart disease, stroke, and type 2 diabetes may be up to 30% lower in people who regularly eat whole grains as part of a low fat diet and a healthy lifestyle. Current recommendations in the UK do not specify a specific daily intake to achieve, but it has been suggested that three portions per day, or around about between 70 to 90 grammes, could provide cardiovascular benefits.
As an example, these three portions could be achieved by eating two medium slices of wholemeal bread and around 40 grammes of whole grain cereal. The mechanism by which whole grain food exerts their beneficial effects against heart disease are not fully understood and might also differ depending on the type of fibres present in the diet. Increased consumption of whole grains might, with high content of stool soluble fibre, such as beta glucan for example, which is found in porridge, could help by reducing cholesterol; the marker for cardiovascular disease.
Increased whole grain intake could also beneficially alter the composition and activity of the gut microbiota with positive consequences on insulin sensitivity and blood pressure; one of the most important independent risk factors for cardiovascular disease. Increased whole grain intake could also increase satiety, therefore, potentially useful for weight management strategies. The fermentation of the fibres present in whole grain by the human gut microbiota might also release beneficial products such as short chain fatty acids, potentially responsible for the physiological effects observed. As such, the current evidence suggests that the implementation of dietary strategies to increase whole grain intake should be promoted. What about yourself? Do you know how many portions of whole grain you usually eat?
The second case study will revolve around plant foods. Whilst dietary prevention of lifestyle related disorders, such as type 2 diabetes, cardiovascular disease, and cancer, has not shown to be due to consuming one particular food or one particular food component, there is, however, strong evidence to support a diet rich in plant foods. These include fruit, vegetables, cereals, nuts, as well as other grains, such as peas and beans. Plant foods are rich sources of fibre, particularly wholegrain cereals as we just discussed. Grains such as fava bean, pea, hemp, lupin, and buckwheat can also be rich sources of plant based protein. They’re generally low in both fat and total energy and can help achieve and obtain a healthy weight.
Plant foods also contain micro-nutrient vitamins and minerals. All of these compounds are essential for us to live and grow.

Substantial improvements in life expectancy over the past 100 years mean that people are living longer, healthier lives than ever before. This has been due to improvements in sanitation, medicines and health care, underpinned by economic growth, improved living standards and the establishment of the welfare state. Diet has changed dramatically over the last 100 years. Do you think nutrition has an important role in the prevention of non-communicable diseases?

Reference:World Health Organisation factsheet on noncommunicable diseases

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Nutrition Science: Food Choice and Behaviour

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