John W. Finley
Many diseases and conditions associated with aging and being overweight are associated with chronic inflammation. Chronic inflammation is different from the acute inflammation that occurs when we have an injury or an infection. Chronic inflammation often has no clinical symptoms initially, but over time can lead to severe incapacitation or life-threatening conditions. Chronic inflammation is associated with cardiovascular disease, Alzheimer’s disease, arthritis, inflammatory bowel diseases and some forms of cancer. Figure 1 illustrates some of the conditions associated with chronic inflammation. Many of these conditions are progressive and develop over several years.
Conditions such as pre-diabetes, which can lead to diabetes and ultimately result in cardiovascular disease, can be a result of chronic inflammation. Obesity is often the trigger that starts this negative cascade of conditions. Obesity can have many side effects, but not all overweight individuals develop symptoms. Unfortunately, a large percentage of obese subjects do eventually develop one or more of the negative side effects. Deposition of fat around the organs and waist, or visceral obesity, is highly associated with risk of diabetes and subsequent cardiovascular disease. Visceral fat in this part of the body is prone to invasion by cells called macrophages, which normally help us fight off acute infection and help remove foreign substances from the body when injured. When the macrophage cells invade the visceral fat, they express genes similar to those involved in infection, resulting in products that cause chronic inflammation.
Modern biochemistry and genomics provide us with the tools to measure changes in the expression of specific genes, which in turn help us understand the pathways involved in inflammation. Understanding the pathways allows us to predict the tools to delay or prevent the negative effects. When the macrophages invade the abdominal adipose tissue, they produce a cytokine known as TNF. This cytokine is involved in chronic inflammation and is a member of a group of cytokines that all stimulate inflammatory responses. One of the inflammatory proteins formed is Cox-2, which is directly associated with both chronic and acute inflammation. When Cox-2 proteins are expressed, it is a direct indication of inflammation.
When TNF increases, another cytokine, NFB, increases. The combination results in oxidative stress in the body. It is this oxidative stress that causes tissue dam age and ultimately leads to inflammatory conditions. Increases in NFB are associated with increased insulin resistance, which initiates the pathway to diabetes.
Macrophage cells kill invading bacteria by releasing oxidizing materials, which invade and kill the invading cells. This is clearly a good thing when we have microbial infection. When these oxygen radicals are produced in healthy tissue, however, it can result in unwanted damage. The end result is oxidative stress, which can result in the inflammatory conditions shown in Figure 1.
Another cause of oxidative stress in the body is chronic high levels of fatty acids and glucose in the blood. High levels of free fatty acids and glucose can result in increased oxidative stress and exacerbate the risk of chronic inflammatory conditions. High levels of free fatty acids are highly correlated with cardiovascular disease and death. Elevated levels of glucose as a result of food choices and the development of insulin resistance are directly associated with diabetes.
The message is that overeating and obesity can lead to excessive levels of free fatty acids and glucose in the blood and visceral adipose tissue deposition. Chronic high levels of glucose or fatty acids can result in oxidative stress. Deposition of fat around the waist also results in more oxidative stress. LSU AgCenter programs are identifying and developing foods rich in antioxidants that can help control oxidative stress. Currently, research is being conducted to identify antioxidants in foods and the potential health benefits of antioxidants in foods. Fruits and vegetables are foods naturally rich in antioxidants.
Antioxidants offer significant potential in reduction of oxidative stress. It must be kept in mind, however, that antioxidants alone cannot completely overcome the stress caused by excessive levels of glucose, free fatty acids in the blood, and obesity.
Foods deliver a number of different types of antioxidants, and one of the major thrusts in functional foods research is to increase the antioxidants in foods. Fruits and vegetables are the best sources of antioxidants, although spices such as rosemary and thyme also produce high levels of antioxidants. Blueberries have captured an enormous growth in sales because they are rich in anthocyanins, which are particularly effective antioxidants.
LSU AgCenter research is focused on identifying potential new sources of antioxidants, understanding how they work, developing technology to deliver them so they are useful, and delivering them in foods consumers will like and eat.
Although the nutrition community stepped up its promotion of more fruits and vegetables in the diet 30 years ago, little has changed. A different approach is to supplement foods commonly eaten with ingredients rich in antioxidant activity. To accomplish this we must find economical sources of effective antioxidants that will help control oxidative stress and chronic inflammation.
Byproducts of food processing are often rich in antioxidants if they can be economically recovered and added back to foods. Several Louisiana crops and byproducts offer opportunities to produce concentrates of antioxidants. Recovery of these materials would generate new business opportunities in the state and enhance health. For example, rice bran is rich in antioxidants, but it also contains lipids that are rapidly oxidized and can reduce the antioxidant value and result in bad flavor. Stabilized rice bran or extracts from the bran can be incorporated in baked products, pasta and food bars, which have excellent flavor and are foods that consumers will eat. Sweet potatoes unfit for market represent sources of antioxidants that can be recovered and added to foods. Lycopene, which is important for prostate health, can be recovered from watermelon not suitable for the market and from rinds.
In summary, obesity and excess fat and carbohydrate in the diet can lead to excess fat deposition and oxidative stress. Oxidative stress leads to chronic inflammatory diseases such as coronary heart disease, Alzheimer’s disease, arthritis and some forms of cancer. The antioxidants in fruits and vegetables offer good protection against these conditions. Many consumers, however, are unable or unwilling to increase consumption of these foods. The LSU AgCenter is conducting research to incorporate antioxidants into other foods that will deliver the needed antioxidant protection to help delay chronic inflammatory diseases.
John W. Finley, Professor and Head, Department of Food Science, LSU AgCenter, Baton Rouge, La.
(This article was published in the fall 2008 issue of Louisiana Agriculture.)