The quality of the diet can have a significant impact on subsequent health outcomes. Low quality diets are increasingly being linked to a higher risk of cardiovascular disease, cancer and obesity. Traditionally, researchers have investigated the aetiology of disease by investigating single nutrients. In the nutritional sciences, this type of thinking worked in the past during the discovery of the vitamin and minerals, where single nutrients can cause single deficiency diseases. Withholding a single nutrient from an animal for a length of time causes a specific disease, which is reversed upon re-introduction of that nutrient to the diet. However, cardiovascular disease, cancer and obesity should be considered groups of disorders, and it is therefore naïve to think that they have a single cause. Because nutrients have interactive effects in vivo, it is important to consider groups of nutrients, when considering these diseases.
Testing a single compound for its effects on physiology is used extensively in the pharmaceutical industry, where there exists an obsession with discovering magic bullets to cure disease. Apart from the discovery of antibiotics, this has been a futile effort that has derived questionable benefit. However, this type of magic bullet thinking has unfortunately infected some nutritional research, which the result that over the past 50 years, resources have been wasted in an attempt to discover a single cause factor for diseases such as cancer and cardiovascular disease. Only recently has a more general holistic viewpoint started to permeate through the nutritional sciences, and as a result great progress has been made. In particular, this thinking has managed to dispel the myth that cholesterol is the cause of cardiovascular disease, and instead replace this meme with the notion that low quality diets are to blame.
Low quality diets are difficult to quantify as metabolism is incredibly complex in animals. However, it is known that a number of characteristics within a diet contribute towards a decreased quality. Diets high in refined carbohydrates are particularly prevalent in Western nations, and are the defining feature of most low quality diets. Introducing refined grains, characterised by a high glycaemic index (GI), low fibre, and a low vitamin and mineral content, is know to increase disease risk considerably. In contrast, whole grains retain the nutrients present in the original plants and are protective of disease. Refined carbohydrates are typified by the processed breakfast cereal, which contains little in the way of nutritional value. Such refined carbohydrates are increasingly being associated with the development of the metabolic syndrome, a disorder thought to increase the risk of developing diabetes and cardiovascular disease.
For example, one group of researchers1, has investigated the association between refined carbohydrates and metabolic syndrome in patients with type 2 diabetes. The study involved 175 subjects with a mean age of 61.1 years, and used a cross-sectional design which assessed the diets of the subjects using weighed 3-day food records. The results showed that subjects with metabolic syndrome had higher GI diets, higher GI breakfasts and lower fibre intakes over the preceding 3-days, when compared to subjects without metabolic syndrome. Using a multivariate analysis, a high GI diet and a low fibre intake were both associated with metabolic syndrome. The authors concluded that the association between metabolic syndrome and high GI low fibre diets were predominately due to breakfast intake. The authors also commented that abnormal high density lipoprotein (HDL) concentrations were associated with the high GI low fibre intake.
These results suggest that low quality breakfasts are associated with metabolic syndrome and may therefore increase risk of cardiovascular disease. This is not surprising because the typical processed Western breakfast cereal is devoid of any meaningful level of nutrition. These results are supportive of other studies that show that eating refined carbohydrate causes disease, and in particular increases the risk of developing metabolic syndrome. Interestingly the micronutrient content of the diets was not assessed in this study. However, the typical highly refined breakfast cereal has much of the micronutrient content removed, along with the fibre, during processing. The mineral chromium is removed in this process, but is essential to the function of the insulin receptor. Because insulin resistance is thought to be pivotal in the development of metabolic syndrome, consumption of chromium deficient cereal may be implicated in this process.
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