Medical importance of dietary betaines

The medicinal effects of betaines have only recently been studied, and this thesis furthers this field. Chapter 2 describes the process of developing a betaine assay in order to assay the betaine content of foods. The final methods are described in section 2.5. Using those methods, foods commonly found the New Zealand diet were assayed and a database of betaine contents in foods can be found in chapter 3. Foods that were high in particular betaines have been studied further, to get an indication of the variation between food samples that is present. This study found that there are only three betaines present in the diet at leyels high enough to have potential metabolic effects: glycine betaine, trigonelline and proline betaine. The database has been used to estimate the average daily intake of glycine betaine, trigonelline and proline betaine at 150-200, 20 and 15 mg/day respectively. A diet was also designed to maximize glycine betaine intake, resulting in an intake of 620 mg/day. Chapters 4 and 5 describe experiments on the effect of dietary betaines on different medical problems. Chapter 4 shows that there is a increase in plasma homocysteine concentrations associated with the consumption of coffee, which is consistent with the hypothesis that trigonelline in coffee interacts with homocysteine homoeostasis. Trigonelline has some antimicrobial properties in certain conditions, and the question of trigonelline in the diet being a potential to be utilized in the treatment or prevention of urinary tract infections (UTI) is addressed in Chapter 5. Due to a number of factors (discussed in section 5.5), the antimicrobial properties of trigonelline have no effect in human urine, and trigonelline is unable to be used to treat or prevent UTI