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Researchers have long known that to live longer, we should eat less and limit our intake of calories. But calories restriction does not mean restricting nutrients. We should always eat nutrient-rich foods.
Limit sugar and starch
All carbohydrates are made up of simple (single-molecule) sugars like glucose, fructose and galactose (from milk). While they provide nutrition, excessive amounts are toxic and we have earlier seen how they contribute (via insulin resistance and leptin resistance) to problems like diabetes and obesity.
Another problem with simple sugars is glycation. These sugar molecules get oxidised easily when exposed to oxygen and free radicals to form inflammatory products called advanced glycation end-products, (AGES). While excess glucose causes glycation easily, excess fructose and galactose have 10 times the glycation effect of glucose. AGEs coat and cause inflammation of all structures that they come into contact with, especially inside the blood circulation. This leads to structural damage and dysfunction.
It destroys cell receptors and DNA, resulting in a breakdown in cellular communication. Caloric restriction essentially stops all these damages. The best way to reduce calories is to limit your intake of sugar and starch. A low glycemic diet is ideal for longevity.
Your body has some 50,000 protein products and you need a regular supply of protein to maintain them. Protein is essential to life.
mTOR and aging
When you eat too much protein, a substance called mTOR (mammalian target of rapamycin) is activated to turn on cell proliferation for growth and reproduction. This, in turn, increases oxidative stress of the mitochondria, the "energy generator" of cells, leading to accelerated ageing and increased cancer risk. So it is important to reduce your protein intake to below the level for mTOR activation.
Besides a high-protein diet, mTOR is also activated by rising insulin and growth factors from a high-carbohydrate diet. Among the 25 amino acids, four - leucine, isoleucine, valine and threonine - are able to induce the release of insulin, just like glucose. Therefore overall caloric restriction with a lower protein diet is essential for longevity and wellness.
Recommended Protein Intake
The recommended daily amount of protein for growth and reproduction is between 1g and 1.5g per kilogram of body weight. An adult weighing 50kg will need at least 50g of protein daily. Since the protein content of most meat or fish is about 30 percent, the recommended daily amount of meat or fish is 200g daily (which provides about 60g of protein). This amount must be divided equally over three meals to avoid activating mTOR.
For active people like children, pregnant women and athletes, the protein intake could safely be increased to 1.5g per kilogram of body weight daily. For seniors to achieve longevity and wellness, the protein intake must be reduced to 0.8g per kilogram of body weight per day. In addition, the protein intake per meal must not exceed 25g to avoid stimulating mTOR for cell proliferation.
This content is adapted, with permission, from Book 1 of 2 : The Wonders of Nutrition by Dr Ang Poon Liat. MBBS, M.MED (PAED), MRCP (UK PAED), FAMS, MD.