Lancet. 2002 Sep 14;360(9336):861-8.
The Effect of Diet on Risk of Cancer
Key TJ, Allen NE, Spencer EA, Travis RC.
Cancer Research UK Epidemiology Unit, University of Oxford, Gibson Building, Radcliffe Infirmary, Oxford OX2 6HE, UK. Tim.Key@cancer.org.uk
Diet-related factors are thought to account for about 30% of cancers in developed countries. Obesity increases the risk of cancers in the oesophagus, colorectum, breast, endometrium, and kidney. Alcohol causes cancers of the oral cavity, pharynx, larynx, oesophagus, and liver, and causes a small increase in the risk of breast cancer. Adequate intakes of fruit and vegetables probably lower the risk for several types of cancer, especially cancers of the gastrointestinal tract. The importance of other factors, including meat, fiber, and vitamins, is not yet clear. Prudent advice is to eat a varied diet including plenty of fruit, vegetables, and cereals to maintain a healthy bodyweight with the help of regular physical activity and to restrict consumption of alcohol.
Excerpt from Unhappy Meals
By Michael Pollan
Eat food. Not too much. Mostly Plants.
THE ELEPHANT IN THE ROOM
In the end, the biggest, most ambitious and widely reported studies of diet and health leave more or less undisturbed the main features of the Western diet: lots of meat and processed foods, lots of added fat and sugar, lots of everything - except fruits, vegetables, and whole grains.*
In keeping with the nutritionism paradigm and the limits of reductionist science, the researchers fiddle with single nutrients as best they can, but the populations they recruit and study are typical American eaters doing what typical American eaters do: trying to eat a little less of this nutrient, a little more of that, depending on the latest thinking. (One problem with the control groups in these studies is that they too are exposed to nutritional fads in the culture, so over time their eating habits come to more closely resemble the habits of the intervention group.) It should not surprise us that the findings of such research would be so equivocal and confusing.
But what about the elephant in the room — the Western diet? It might be useful, in the midst of our deepening confusion about nutrition, to review what we do know about diet and health.
What we know is that people who eat the way we do in America today suffer much higher rates of cancer, heart disease, diabetes and obesity than people eating more traditional diets. (Four of the 10 leading killers in America are linked to diet.)
Further, we know that simply by moving to America, people from nations with low rates of these “diseases of affluence” will quickly acquire them.
"Nutritionism" by and large takes the Western diet as a given, seeking to moderate its most deleterious effects by isolating the bad nutrients in it — things like fat, sugar, salt — and encouraging the public and the food industry to limit them.
But after several decades of [this] nutrient-based health advice, rates of cancer and heart disease in the U.S. have declined only slightly (mortality from heart disease is down since the ’50s, but this is mainly because of improved treatment), and rates of obesity and diabetes have soared.
No one likes to admit that his or her best efforts at understanding and solving a problem have actually made the problem worse, but that’s exactly what has happened in the case of nutritionism.
Scientists operating with the best of intentions, using the best tools at their disposal, have taught us to look at food in a way that has diminished our pleasure in eating it while doing little or nothing to improve our health.
Perhaps what we need now is a broader, less reductive view of what food is, one that is at once more ecological and cultural. What would happen, for example, if we were to start thinking about food as less of a thing and more of a relationship?
In nature, that is of course precisely what eating has always been: relationships among species in what we call food chains, or webs, that reach all the way down to the soil. Species co-evolve with the other species they eat, and very often a relationship of interdependence develops: I’ll feed you if you spread around my genes. A gradual process of mutual adaptation transforms something like an apple or a squash into a nutritious and tasty food for a hungry animal.
Over time and through trial and error, the plant becomes tastier (and often more conspicuous) in order to gratify the animal’s needs and desires, while the animal gradually acquires whatever digestive tools (enzymes, etc.) are needed to make optimal use of the plant.
“Health” is, among other things, the byproduct of being involved in these sorts of relationships in a food chain — involved in a great many of them, in the case of an omnivorous creature like us. Further, when the health of one link of the food chain is disturbed, it can affect all the creatures in it. When the soil is sick or in some way deficient, so will be the grasses that grow in that soil and the cattle that eat the grasses and the people who drink the milk. Or, as the English agronomist Sir Albert Howard put it in 1945 in “The Soil and Health” (a founding text of organic agriculture), we would do well to regard “the whole problem of health in soil, plant, animal and man as one great subject.” Our personal health is inextricably bound up with the health of the entire food web.
In many cases, long familiarity between foods and their eaters leads to elaborate systems of communications up and down the food chain, so that a creature’s senses come to recognize foods as suitable by taste and smell and color, and our bodies learn what to do with these foods after they pass the test of the senses, producing in anticipation the chemicals necessary to break them down. Health depends on knowing how to read these biological signals: this smells spoiled; this looks ripe...
This is easier to do when a creature has long experience of a food, and much harder when a food has been designed expressly to deceive its senses — with artificial flavors, say, or synthetic sweeteners.
Note that these ecological relationships are between eaters and whole foods, not nutrients.
Even though the foods in question eventually get broken down in our bodies into simple nutrients, as corn is reduced to simple sugars, the qualities of the whole food are not unimportant — they govern such things as the speed at which the sugars will be released and absorbed, which we’re coming to see as critical to insulin metabolism.
Put another way, our bodies have a longstanding and sustainable relationship to corn that we do not have to high-fructose corn syrup.
Such a relationship with corn syrup might develop someday (as people evolve superhuman insulin systems to cope with regular floods of fructose and glucose), but for now the relationship leads to ill health because our bodies don’t know how to handle these biological novelties. In much the same way, human bodies that can cope with chewing coca leaves — a longstanding relationship between native people and the coca plant in South America — cannot cope with cocaine or crack, even though the same “active ingredients” are present in all three.
Reductionism as a way of understanding food or drugs may be harmless, even necessary, but reductionism in practice can lead to problems.
*The sentences in bold emphasize some of Purium's main reasons for choosing this thought-provoking article. - Purium Editor