Best Upper Body Kettlebell Exercises
Water Vital but Often Ignored Water is the major component in both foods and the human body: You are composed of about 50-60% water. Your need for other nutrients, in terms of weight, is much less than your need for water. You can live up to 50 days without food but only a few days without water.
Water is distributed all over the body, among lean and other tissues and in blood and other body fluids. Water is used in the digestion and absorption of food and is the medium in which most chemical reactions take place within the body. Some water-based fluids, such as blood, transport substances around the body; other fluids serve as lubricants or cushions. Water also helps regulate body temperature.
Water is contained in almost all foods, particularly in liquids, fruits, and vegetables. The foods and beverages you consume provide 80-90% of your daily water intake; the remainder is generated through metabolism. You lose water in urine, feces, and sweat and through evaporation from your lungs. Most people can maintain a healthy water balance by consuming beverages at meals and drinking fluids in response to thirst. The Food and Nutrition Board has set levels of adequate water intake to maintain hydration. All beverages, including those containing caffeine, can count toward your total daily fluid intake. Under these guidelines, men need to consume about 3.7 total liters of water, with 3.0 liters (about 13 cups) coming from beverages; women need 2.7 total liters, with 2.2 liters (about 9 cups) coming from beverages. About 20% of daily water intake comes from food. (See Table 1 in the “Nutrition Resources” section at the end of the chapter for recommendations for specific age groups.) If you exercise vigorously or live in a hot climate, you need to consume additional fluids to maintain a balance between water consumed and water lost. Severe dehydration causes weakness and can lead to death.
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Other Substances in Food
Many substances in food are not essential nutrients but may influence health.
Antioxidants When the body uses oxygen or breaks down certain fats or proteins as a normal part of metabolism, it gives rise to substances called free radicals. Environmental factors such as cigarette smoke, exhaust fumes, radiation, excessive sunlight, certain drugs, and stress can increase free radical production. A free radical is a chemically unstable molecule that reacts with fats, proteins, and DNA, damaging cell membranes and mutating genes. Free radicals have been implicated in aging, cancer, cardiovascular disease, and other degenerative diseases like arthritis.
Antioxidants found in foods can help protect the body by blocking the formation and action of free radicals and repairing the damage they cause. Some antioxidants, such as vitamin C, vitamin E, and selenium, are also essential nutrients. Others such as carotenoids, found in yellow, orange, and dark green leafy vegetables are not. In general, fruits and vegetables and foods that contain them have a high antioxidant value. Research has identified herbs, spices, berries, nuts and chocolate as some of the top antioxidant ingredients and foods.
Phytochemicals Antioxidants fall into the broader category of phytochemicals, substances found in plant foods that may help prevent chronic disease. In the past 30 years, researchers have identified and studied hundreds of different compounds found in foods, and many findings are promising. For example, certain substances found in soy foods may help lower cholesterol levels. Sulforaphane, a compound isolated from broccoli and other cruciferous vegetables, may render some carcinogenic compounds harmless. Allyl sulfides, a group of chemicals found in garlic and onions, appear to boost the activity of immune cells. Phytochemicals found in whole grains are associated with a reduced risk of cardiovascular disease, diabetes, and cancer. Carotenoids found in green vegetables may help preserve eyesight with age. Further research on phytochemicals may extend the role of nutrition to the prevention and treatment of many chronic diseases.
To increase your intake of phytochemicals, eat a variety of fruits, vegetables, and grains rather than relying on supplements. Like many vitamins and minerals, isolated phytochemicals may be harmful if taken in high doses. In many cases, their health benefits may be the result of chemical substances working in combination. The role of phytochemicals in disease prevention is discussed further in Chapters 11 and 12.
QUESTIONS FOR CRITICAL THINKING AND REFLECTION
Experts say that two of the most important factors in a healthy diet are eating the “right” kinds of carbohydrates and eating the “right” kinds of fats. Based on what you’ve read so far in this chapter, which are the “right” carbohydrates and the “right” fats? How would you say your own diet stacks up when it comes to carbs and fats?