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Research is the engine of science. But that engine should not be idling, it should be steadily propelling science forward. The extent of that forward motion is to be found in the estimated 10,000 papers spewed out every day by the world鈥檚 45,000 or so peer-reviewed scientific journals.聽
Some of these papers are excellent and nudge science along, but there are also ones that describe sloppy, methodologically weak and over-interpreted research. Or in the worst-case scenario, present data that is fraudulent.聽
Then there are studies that may have been properly designed, carried out by reputable scientists and report reliable data, but do not add to our existing body of knowledge in any significant way. These can be likened to that idling engine.
The question I ask myself when perusing a paper is whether it reports any novel information that may somehow benefit society. Are the time and funds spent on the research justified? This is particularly pertinent when it comes to the ever-increasing number of studies that explore the relationship between health and diet.聽
Let me illustrate with an example. 鈥溾�� was published in the Journal of the American Medical Association (JAMA) by a group of Slovenian and Swedish MDs and PhDs who analyzed data gathered by the Swedish National Study on Aging.
Between 2001 and 2004, Swedish scientists enlisted 1,865 seniors with no symptoms of dementia who were then followed for an average of eight years. Periodically the participants filled out food frequency questionnaires and had their blood tested for markers that signal a risk for Alzheimer鈥檚 disease. Eventually 240 subjects developed dementia. Some data dredging by the authors of the JAMA paper found that subjects who had elevated biomarkers for Alzheimer鈥檚 were less likely to eventually develop the disease if they adhered to a 鈥渉ealthier dietary pattern,鈥� which in this case was one with 鈥渓ower inflammatory potential.鈥�
What exactly is a diet with 鈥渓ower inflammatory potential?鈥� Inflammation is the body鈥檚 protective response to an injury, infection or irritation. It is a complex, multi-pronged process that involves dilation of blood vessels so that white blood cells can rush to the scene and attempt to remedy the affront, be it an invasion by microbes, irritation by a splinter, or just a stubbed toe.聽
Different types of white blood cells have different functions, and they actually 鈥渢alk鈥� to each other to co-ordinate the specific action required. This communication is through signalling proteins called cytokines, with 鈥渋nterleukins鈥� being a typical example.聽
鈥淟eukocyte鈥� is the general term for white blood cells, so 鈥渋nterleukins鈥� are signals passed between white blood cells. There are a number of other cytokines as well, including 鈥渢umour necrosis factors,鈥� 鈥渋nterferons鈥� and 鈥渃hemokines.鈥� These can be tested for in the blood and are recognized as markers of active inflammation.聽
Cytokines also stimulate the liver to produce C-reactive protein (CRP), which helps remove injured or dead cells and also serves as a marker of inflammation.
Acute inflammation is useful. A skin prick by a thorn causes blood vessels to dilate, allowing immune cells to rush to the site. The area becomes red, warm, swollen and painful as bacteria are attacked, damaged tissue is cleared, and healing ensues.聽
The immune system similarly swings into action when a cold virus invades the nose or when a hand touches a hot stove. In such cases, once the immune cells have done their job, they send out 鈥渟tand down鈥� signals, and immune activity winds down.聽
However, inflammation can also be chronic, meaning that there is some sort of continuing irritation that causes low-grade immune activity. This can be due to smoking, inhaling polluted air, chronic infection such as hepatitis, damage to the walls of arteries by the buildup of plaque, or the accumulation of abdominal fat. In the latter case, fat cells expand causing them to be stressed, which results in sending out signals that they are being damaged, and the immune system responds.
Then there is diet. Some components in food are perceived by the body as unwelcome invaders and spark immune activity that, if prolonged, causes ongoing cytokine release that can result in all sorts of negative effects 鈥� ranging from insulin resistance to destabilizing arterial plaque. Rupture of arterial plaque can lead to a heart attack.聽
Chronic inflammation can also escalate cell turnover, meaning an increased risk of cancer due to DNA damage.聽
Basically, prolonged immune activity, whatever the cause, results in the body鈥檚 repair system turning into a source of collateral damage, injuring the tissues it is supposed to protect.
Let鈥檚 now address the concept of an anti-inflammatory diet:
Based on an extensive literature search of cell culture studies, animal experiments with specific nutrients, and human epidemiological studies in which the relationship between diet and inflammation biomarkers was determined, researchers have developed a 鈥渄ietary inflammatory index (DII).鈥� Through a complex formula, various foods and 45 specific nutrients were assigned numerical values based on how they affect inflammatory markers.聽
Excessive calorie intake, sugar, trans fats, refined carbohydrates, deep-fried foods, red and processed meat are classified as inflammatory. Vegetables, polyphenol-rich fruits such as berries, legumes, whole grains, nuts and seeds, fatty fish, olive oil, fermented foods such as yogurt, herbs and spices like turmeric, ginger and garlic, as well as green tea and coffee, are deemed to be anti-inflammatory.聽
Based on the DII and food frequency questionnaires, the anti-inflammatory effect of a specific diet can then be calculated.
