| NUTRITION AND CHRONIC DISEASE
|
| The major groups of diseases, which are affected by diet, are coronary heart disease and cancer. They are also the two main causes of death in the developed world.
|
| Diet plays an important role in the prevention of coronary disease
|
| Nutrients which affect atherosclerosis are dietary cholesterol, saturated fat and trans-fatty acids. Excessive caloric intake and consequent obesity also facilitate atherosclerosis. High dietary cholesterol and high saturated fat decrease the LDL receptor expression mediated through an increase in the intracellular cholesterol content in the hepatocytes: this leads to an increase in plasma cholesterol concentration (Chapter 17). Foods containing saturated fatty acids (full-fat milk, cheese, butter, and red meats) are atherogenic in excess. The rationale behind the low-cholesterol diets is that LDL receptor expression can be increased if dietary cholesterol content is sufficiently low. The typical Western diet contains approximately 400-500 mg of cholesterol daily. The intake required to achieve reduction in plasma cholesterol is much lower: below 200 mg or even below 100 mg daily (incidentally, when the intake is above 500 mg, further increase in intake does not necessarily lead to further increase in cholesterol concentration).
|
| Nutrients that seem to be protective against atherosclerosis include polyunsaturated ω-6-rich fatty acids (contained in vegetable oils) and ω-3-rich fish and fish oils, monounsaturated fat, and soluble fibre such as beta-pectin. Polyunsaturates reduce plasma cholesterol concentration. The ω-3 fatty acids reduce triglycerides by decreasing VLDL synthesis and increasing its catabolism. They are also antithrombotic: fish oil inhibits thromboxane and PDGF synthesis, reduces blood viscosity and enhances fibrinolysis. Monounsaturated fats increase the concentration of HDL, increase insulin sensitivity and decrease plasma triacylglycerol (triglyceride) concentration.
|
| page 311 |  | | page 312 |
| Diets low in fat and cholesterol have been a hallmark of cardiovascular prevention for decades
|
| These diets normally result in approximately 10% decrease in serum cholesterol if applied during clinical trials and, unfortunately, to a much lesser decrease (usually below 5%) when applied in general population. Alcohol seems to be protective against coronary disease but if taken in excess it carries multiple other risks, obesity included. Unfortunately, the low fat diets, if the protein content is kept constant, need to be high in carbohydrates. High-carbohydrate low-fat diet is, however, not without problems. The main practical problem is that, in spite of recommendations to use predominantly complex carbohydrates, in many populations refined sugars constitute too high a proportion of carbohydrate intake, and this promotes obesity. High carbohydrate diets may also lead to hypertriglyceridemia. Finally, low-fat diets seem to decrease HDL-cholesterol by 10-20%.
|
|
