In 1992 the American Department of Agriculture officially published diet guidelines that came to be known as the 'food pyramid'. The geometric diagram illustrating the right proportion of different foods to be included in the diet was so efficient that it has been considered for years an excellent nutritional model.

Today it has been updated by new scientific studies and evidence. Walter C. Willett  and Meir J. Stampfer, professors of dietology at the  Harvard School of Public Health, have devised a revolutionised pyramid. They have rearranged the hierarchy of different foods, making greater distinctions between those in the same nutrient categories (especially carbohydrates and meat), above all capable of bearing in mind varying lifestyles. 

The biggest news concerns the fact that daily physical exercise features as the basis of everything, recognised as the best way of controlling weight and serious disease such as obesity, cardiopathy and cancer. According to the two researchers the most efficient way of avoiding obesity, apart from exercise, is by limiting the total amount of calories as opposed to reducing calories provided by fats.

The next step up, once occupied by bread, cereals, white rice and pasta with daily portions of between 6-11, has been partly modified, as wholemeal carbohydrates are now the only foods to appear. The evolution is the introduction of a distinction between refined carbohydrates (white rice, white bread, potatoes. pasta and cakes) and wholemeal carbohydrates (wholemeal bread and pasta).

In fact it has been proved that overloading the diet with refined carbohydrates is risky. The refining process removes vitamins, fibre and minerals and produces starch that is easily able to be assimilated. As a consequence these carbohydrates considerably increase the level of glucose in the blood compared to those made from wholemeal flour, resulting in the increased risk of diabetes and cardiovascular disease. Boiled potatoes also appear in this category and therefore should be eaten sparingly, as the other refined carbohydrates. On the other hand the wholemeal foods that lower the risk of the above problems should be eaten regularly.

Fats also feature on this level and they, too, have undergone important changes. Notice however that we are not talking about saturated fats found in meat or butter but monounsaturated and vegetable polyunsaturated ones. It has been proved that several Mediterranean populations, despite having a high percentage of calories in their diets provided by fats, do not have a higher risk of coronary disease compared to populations with a similar or even lower fat content in their diets (eg. the Eastern Fins or Japanese); actually the risk was even lower.

So which are the healthy fats? Those contained in the Mediterranean diet: olive, Soya, corn, sunflower and peanut oils are recommended to be used at almost all meals because it has been noted that a good amount of fats in the diet is essential for the healthy functioning of our bodies. Fats to be limited, appearing at the very top of the pyramid, are therefore saturated ones: butter and lard.

Fruit and vegetables (apart from potatoes) are confirmed as very positive: they should be eaten in abundance (at least 2-3 portions daily, especially vegetables).

Another problem with the old pyramid was the inability to distinguish between red meats (beef, pork and mutton) and other animal and vegetable protein groups (poultry, fish, eggs, pulses, nuts and other dried fruit). Studies have shown that substituting red meat with chicken and fish means running less risk of cardiovascular disease and cancer of the colon. Red meat should be limited because it contains saturated fats and cholesterol and its consumption has been linked to an increased risk of cardiovascular disease, type 2 diabetes and cancer of the colon.

The fourth step features nuts and pulses (from 1-3 portions a day) because of the fact that they provide non-animal proteins and contain mainly unsaturated fats (peanut). Nuts are rich in omega-3, precious health allies, and are foods that tend to satisfy and therefore consistently reduce the need to consume other foods.

Fish, poultry and eggs feature immediately afterwards (0-2 portions a day): these are the most recommended sources of animal proteins. An egg a day does no harm, even though it is a food that should be kept an eye on because of its cholesterol content.

The old pyramid recommended 2-3 portions a day of milk, yoghurt and cheese, which has been revealed to be too much: calcium is a fundamental element but its role in promoting healthy bones should not be overrated. In fact excessive consumption produces a higher risk of certain types of cancer (of the prostate in men and ovaries in women). Usually the correct quantity of calcium per day can be obtained by drinking a glass of milk or eating a portion of cheese.

Unless otherwise directed, even a good glass of red wine can feature on the pyramid for is protective qualities of the cardiovascular system, as verified by medical research. Additionally, vitamin supplements are recommended as part of our diets.

From the studies carried out by the authors of the new pyramid,  Willett and Stampfer, it has been proved that those who follow the eating plan reduce the risk of chronic and cardiovascular disease and, thanks to weight control and physical exercise, also numerous types of cancer. Obviously the pyramid is intended for healthy adults.