Determinants of food and nutrition

Using the above definitions, it becomes clear that nutrition (or diet) is actually the result of two major determinants:

1. Food supply (range and quality of products available)

2. Eating behaviour of people (food choices, food preparation)

But these two determinants of nutrition are themselves under the control of a broad range of other (sub)determinants, as also noted in the WCRF/AICR report (2007). These concern important factors like:

a. Type of society (gatherer-hunter, peasant-agriculture, or urban-industrial)

b. Globalization and food technology

c. Health policy (protection and promotion)

d. Social environment: socio-economic and personal determinants of behaviour

Interestingly, historical and recent changes in some of the subdeterminants of food supply seem to coincide with significant changes in the rates of most common cancers. Together with the change in cancer patterns observed in immigrant populations, this indicates that environmental factors (including nutrition) play an important role in the cause of cancer. Moreover, it also suggests that cancer is a preventable disease at least to a certain degree.

Two important aspects of nutrition

Regarding the health effects of nutrition, a distinction must be made between two important aspects:

1. Quantity: in terms of energy intake

2. Quality: in terms of dietary composition

If the intake of energy-providing nutrients is too low, the result will be malnutrition and eventually starvation. However, if overall energy intake is too high (i.e. exceeding energy expenditure), this will lead to weight gain, which may result in overweight and ultimately obesity.

Overweight and obesity are risk factors for a number of chronic diseases, including cancer. To date, this forms a serious problem in adults, but even more so in children. Especially because it appears very difficult for an overweight or obese person to regain normal weight again. For obese kids this therefore implies that they will have a lifetime long increased risk for certain chronic diseases. This is already reflected in the occurrence at much younger ages of typical diseases like diabetes type 2, which are normally associated with elderly people. Finally, overweight and obesity will also reduce life expectancy.

The average daily composition of the diet will determine whether the intake of all essential nutrients (macro and micro) is adequate. If, for instance, the intake of vitamins and minerals is too low, this may result in deficiency diseases, some of which can be life-threatening. Current scientific insights however, demonstrate a more complex relationship between nutrition, diet and health, particularly for the chronic diseases (often called ‘lifestyle diseases’).

Not only an inadequate intake of vitamins and other micronutrients is unhealthy, also an excessive intake of specific macronutrients, such as the trans and saturated fatty acids, is known to have adverse effects on health.

Conversely, beneficial effects have been ascribed to certain non-nutrients, which are said to protect against some chronic illnesses, including several forms of cancer. This holds in particular for food constituents like fibre and certain secondary plant metabolites (such as polyphenols and lignans), found in fruit and vegetables.

Physical activity: role and determinants

Of course, the quantitative aspect of nutrition (amount of energy intake) is not the single determinant of weight gain. What really matters is the balance between energy intake and expenditure (energy balance).

Physical activity is the major determinant at the expenditure side of the energy balance. It can prevent weight gain at all ages, thereby decreasing the health risks of being overweight or obese. Regarding the (sub)determinants of physical activity itself we must again realize that it is the result, just like nutrition, of ‘supply’ on the one side , and ‘behaviour’ on the other side.

Due to urbanisation and industrialisation, the overall levels of physical activity have declined over the past century, in particular (but not exclusively) in high-income countries. These changes, moreover, seem to correlate with the changes observed in cancer patterns in these countries. This suggests again that cancer is a partly preventable disease.

The supply side concerns the possibilities and challenges to become physically active as determined by local infrastructure, employers, labour type and environment, access to cars and motorcycles, PC use, TV use etc. But, it is also influenced by the opportunities offered by schools, sports clubs etc. On the behaviour side, government promotion, social environment and personal determinants are likely to play an important role.