Human foods are made up of essentially six basic component types (five groups of nutrients and water), each of which has different functions in the body (A). Carbohydrates and lipids represent our main energy sources. Proteins, vitamins, minerals, and trace elements are essential for growth and development of tissues. Water, proteins, and vitamins are needed for metabolism as well as for its regulatory functions. While energy nutrients (carbohydrates, lipids, proteins) are partially interchangeable in terms of their use, vitamins, minerals, and trace elements always play very specific roles. Consequently, a lack of any of these components results in nutrient-specific—albeit not always symptomatic—deficiencies. The commonality of all nutrient deficiencies is that they interfere primarily with growth. Consequently, growth rates can be used to demonstrate the value of balanced nutrition. Here is an example: in 1880, only 5% of male college students were over 1.80 m (6 ft) tall, by 1955 that percentage had reached 30%. Improved availability of nutrients since the beginning of the twentieth century has greatly increased life expectancy. Even though theoretical "availability" is more than sufficient in industrialized countries today, major improvements may still be possible through adjustments of nutrient ratios. According to present knowledge, a nutrition that prevents disease can be described in the following simplified manner: lipids <35% (i.e., less than 35 % of total calories consumed), and predominantly from plant sources; proteins ~15%, also predominantly from plant sources; and carbohydrates >55%, with a high fiber content. This means a reduction in foods from animal sources and consumption of a varied array of plant foods with a high proportion of fruits and vegetables, all minimally processed.

Such general recommendations are not sufficient, though, since there is great diversity among people (B). Nutrition professionals (nutritional scientists, home economists, dietitians, physicians, etc.) need detailed information about individual nutrients to do justice to all the complexity. For this reason, many countries have developed recommendations intended to represent basic guidelines for desirable nutrient intakes. In the U.S., these recommendations are issued by the Food and Nutrition Board under the National Research Council. The most recent ones, the Dietary Reference Intakes (DRI), were established in conjunction with the Canadian Health authorities. As nutritional science evolves, these recommendations are revised periodically, and new findings challenge old ideas all the time. On the other hand, external factors are changing as well. Over the past decades, many occupations have progressively evolved towards lower levels of physical activity, and, in many cases, increasing income levels. These factors have a major impact on food choices and nutrient requirements.

- A. Basic Components of Foods

  • B. Factors with Short or Long-Term Impact on Food Choices -
  • economic

Personal traits fe>ts


Nutritional . education,

  • habits, availa-\^Pe,n®"„ knowledge, bility in restau- trad,tl ,"u|e manners,
  • ethnic background rants, childhood habits
  • quot;«to.

Factor category

Price, image, appearance, taste, packaging, nutritional value, availability

Individual factors with direct and indirect effects

3. Factors directly affecting nutritional behavior

Preventive Nutrition: A Science in Flux

Controversy is an integral part of nutritional science. Like many other aspects, preventive nutrition is a controversial issue. During the past decades, reducing fat intake while increasing carbohydrate intake was recommended across the world. These recommendations were based on the observation that, in the Western industrial nations, high fat intakes seemed to correlate with a high incidence of coronary artery disease. Even though many details about the effects of various fatty acids had been known since the sixties, the message was simplified to state "Fats are bad." It was assumed that a general reduction in fat intake would automatically lead to a reduced load of saturated fatty acids. Thus, low-fat diets became a standard. The food industry gladly picked up on this message, especially in the U.S. where low-fat products have a high market-share. Admonitions that called this fat-free strategy arbitrary were published repeatedly, but remained largely unheard.

As early as three decades ago, some scientists proposed that a high carbohydrate intake—or rather the intake of high-glycemic index foods (see p. 68)— might lie at the root of many degenerative diseases. As early as 1972, the American physician Dr. R.C. Atkins proposed a nutritional revolution by recommending consumption of more fats and fewer carbohydrates. The recent publication of a new food pyramid by Harvard scientists (A) gives new support to his thesis.

While whole grain products should be part of every meal, all foods with a high glycemic index, like white bread, baked potatoes, polished rice, pasta, and sweets have been banned into the pyramid's upper levels. Their approach differentiates between refined and whole, simple and complex carbohydrates, taking into account their glycemic index and glycemic load. Additionally, strict distinctions are drawn between various types of fatty acids: vegetable oils are placed at the base, milk products, butter, and red meat moved up. Micro-nutrient intakes appear to be suboptimal regardless of such "healthy" nutrition; hence, multivitamin and mineral supplements are recommended.

Government authorities have not yet subscribed to these opinions (B). Their recommendations still consider a high overall fat intake to be the main problem, while carbohydrate foods represent the basis of the pyramid. No distinction is made between foods with high and low glycemic loads. It remains to be seen whether the official recommendations on preventive nutrition will change based on these recent developments.

To emphasize preventive and therapeutic aspects of nutrition, they are highlighted with orange bars next to the text. The orange bars mark those passages that pertain to prevention or therapy, and clinical or nutritional medicine.

- A. Harvard Food Pyramid -

Red meat and butter, use sparingly

White rice, white bread, potatoes, pasta, and sweets, use sparingly

Dairy products or calcium supplements

Red meat and butter, use sparingly

White rice, white bread, potatoes, pasta, and sweets, use sparingly

Dairy products or calcium supplements

Mycorrhiza Rice

Fish, poultry, and eggs Nuts and legumes

- B. USDA Food Pyramid

Mycorrhiza Rice
Low Carb Diets Explained

Low Carb Diets Explained

You can burn stored body fat for energy and shed excess weight by reducing the carbohydrate intake in your diet. Learn All About The Real Benefits of Low Carb Diets And Discover What They Can Really Do To Improve The Quality Of Your Life Today.

Get My Free Ebook

Post a comment