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Research Newsletter-Fall/Winter 2006

The Beverage Guidelines: What Should You Drink to Stay Healthy?



Balz Frei, Ph.D.
LPI Director and Endowed Chair
Professor of Biochemistry and Biophysics



Why Do We Need Beverage Guidelines?

The Beverage Guidelines were developed by Drs. Barry Popkin, Lawrence Armstrong, George Bray, Benjamin Caballero, Walter Willett, and me, and published this year in The American Journal of Clinical Nutrition ("A new proposed guidance system for beverage consumption in the United States," Am. J. Clin. Nutr. 83: 529-42, 2006). The Beverage Guidance Panel was assembled to provide guidance on the relative health and nutritional benefits and potential health risks of various beverage categories by systematically reviewing the relevant scientific literature.

We undertook this project to understand the effects of beverages on total energy intake. (Note that "energy" is used synonymously with "calories" throughout this article.) We were also concerned about the increased use of sugar in the global diet. For instance, in the United States the average adult consumes over 21% of total calories from beverages—more than double what it was several decades ago. Between 1977 and 2001, the proportion of energy obtained from calorically sweetened soft drinks and fruit drinks (which are different from fruit juices) has increased from 3.9% to 7.1% of all daily calories (from 70 to 189 kcals per day) for the average American aged two and older. These trends are echoed in many countries, where sugar intake from many different sweetener sources has increased considerably in the past 30 years, much of which has come from beverages.

The Beverage Guidance System

Our panel ranked water as the preferred beverage to fulfill daily fluid needs for adults, followed by tea and coffee, lowfat (1.5% or 1%) and skim (nonfat) milk and soy beverages, noncalorically sweetened beverages, beverages with some nutritional benefits (fruit and vegetable juices, whole milk, alcohol, and sports drinks), and—with the lowest priority—calorically sweetened, nutrient-poor beverages.

In coming up with this rank order, we considered the following characteristics of beverages:

  • Energy and nutrient density
  • Contribution to total energy intake and body weight
  • Contribution to daily intake of essential nutrients
  • Evidence for beneficial health effects
  • Evidence for adverse health effects

Based on this rationale, different combinations of beverages can be used to fulfill the fluid needs of a healthy person.

Water

Water consumption is necessary for normal metabolism and physiological function and may provide essential minerals, such as calcium, magnesium, and fluoride. Potable water is very safe and has no adverse health effects. Acute dehydration results in impaired cognition, moodiness, poor thermoregulation, reduced cardiovascular function, and impaired physical work capacity. In general, excess water intake does not cause adverse effects in healthy individuals with properly functioning kidneys because the kidneys can produce a large volume of urine in a relatively short period of time to correct any disturbance.

Tea and Coffee

Black, green, and oolong teas are the three main categories of tea consumed in the world. Tea provides a variety of flavonoids and antioxidants, as well as a few micronutrients, such as fluoride. While there is solid evidence that tea protects against chemically induced cancers in experimental animals, it remains unclear whether tea consumption lowers cancer risk in humans. Tea also provides some amino acids, mainly L-theanine, which has been claimed to cause a relaxed, yet alert state of mind and improve immunity. Tea consumption may also increase bone density, reduce tooth decay and cavities, and lower formation of kidney stones. In addition, epidemiological studies suggest that daily consumption of at least three cups of tea is associated with a modest decrease in the risk of myocardial infarction (heart attack). Addition of sugar, milk, or cream to tea and coffee would make these beverages less desirable due to increased energy and fat content.

With respect to coffee consumption, several studies have observed significant inverse associations with the risk of type 2 diabetes. A modest inverse association between decaffeinated coffee consumption and risk of type 2 diabetes has also been observed, suggesting that compounds other than caffeine may contribute to risk reduction. High intakes of coffee have been associated with significant reductions in colorectal cancer risk in many studies, but others have not found such significant associations. Coffee and caffeine consumption have been consistently associated with significant reductions in the risk of Parkinson's disease in men but not women, which may be due to the modifying effects of estrogen. Boiled, unfiltered coffee, in contrast to normal filtered coffee, has been found to have adverse cardiovascular effects due to increased serum cholesterol.

There is more caffeine in coffee than in tea. Although caffeine is a mild diuretic, human studies indicate that caffeine consumption of up to about 500 milligrams per day does not cause dehydration. A caffeinated beverage's fluid content compensates for its acute diuretic effect. To date, the evidence suggests that moderate caffeine intake up to 400 milligrams per day is not associated with increased risk of heart disease, hypertension, osteoporosis, or high cholesterol. Pregnancy and aging may affect an individual's sensitivity to caffeine. Pregnant women are often advised to limit caffeine consumption because caffeine intakes higher than 300 milligrams per day have been associated with increased risk of miscarriage and low birth weight.

Some studies indicate that the magnitude of caffeine's effect is smaller at low and high intake levels but greater at intermediate levels. Such a relationship has been reported for exercise performance time, reaction time, vigilance, information processing, and mood but may not exist for all physiological and psychological responses.

Low-fat (1.5% or 1%) and Skim (Nonfat) Milk and Fortified Soy Beverages

For children, milk is currently the main source of vitamin D and calcium. Milk is also an excellent source of high quality protein. Low-fat and skim milk, including low-fat yogurt drinks, can contribute to a healthy diet but are not essential for it. Fortified soy milk is a good alternative for individuals who prefer not to consume cow's milk, although soy milk cannot be legally fortified with vitamin D in the United States and some other countries. Soy milk also is a good source of calcium, providing about 75% of the calcium bioavailable from milk. Yogurt drinks have lower lactose content than milk and may be preferred by individuals with reduced lactose tolerance. In general, low-fat dairy beverages and fortified soy milk are important sources of protein, calcium, and other essential micronutrients.

A number of beneficial and some detrimental health effects have been attributed to the consumption of cow's milk. At present, there is insufficient scientific evidence to support an effect of milk or dairy products on weight loss, despite heavy advertising by the dairy industry. Milk may improve bone health; however, the benefits of higher calcium intake on bone mineral density are not maintained if the high intake is reduced. Milk is an important source of calcium and vitamin D due to fortification, particularly for children and adolescents. Milk products also contribute to the intake of essential nutrients in children and adolescents. There is, however, some evidence that milk may increase the risk of aggressive prostate cancer and possibly some other cancers, due to the presence of insulin-like growth factor.

Noncalorically Sweetened Beverages

The noncalorically sweetened beverages (diet sodas and other "diet" drinks) are preferable to calorically sweetened beverages (regular sodas) because they provide water and sweetness but no calories. There is no scientific evidence that noncaloric sweeteners like aspartame increase cancer risk in humans. Evidence is emerging suggesting that the high sweetness of noncalorically sweetened beverages may contribute to a conditioning for a high preference for sweetness. Thus, these beverages are less desirable than water, tea, or coffee.

Caloric Beverages with Some Nutrients

Fruit juices (100% juice) provide most of the nutrients of their natural source but are also relatively high in energy content and may lack fiber and other beneficial compounds present in the whole fruit. Vegetable juices, such as tomato and multi-vegetable juices, are a healthy alternative to fruit juices. They have fewer calories than orange or other fruit juices but usually have significant amounts of added sodium, which is a risk factor for hypertension.

Whole (full-fat) milk contains a large amount of calories and excessive saturated fat and should be avoided. The adverse effects of saturated fats on the risk of cardiovascular diseases are well documented.

Sports drinks contain 50 to 90% of the energy in calorically sweetened soft drinks and provide small amounts of sodium, chloride, and potassium. They help athletes during high endurance activities but should be consumed sparingly, except for endurance athletes, because they provide "hidden" calories.

For adults, alcoholic beverages consumed in moderation can have health benefits, such as a significantly decreased risk of coronary heart disease and ischemic stroke, and possibly a reduced risk of type 2 diabetes. Moderate intake is defined as the daily consumption of no more than one drink for women and two for men. (One drink is 12 fl oz of beer, 5 fl oz of wine, or 1.5 fl oz of distilled spirits.) Alcoholic beverages contain calories, and excessive alcohol consumption is linked to serious health and social problems. The major health benefits of alcoholic beverages are attributed to alcohol per se, which increases serum levels of high-density lipoprotein (the "good" cholesterol). Current evidence suggests some additional health benefits of flavonoids in red wine or dark beer.

Calorically Sweetened Beverages

Calorically sweetened beverages with high energy density and very limited amounts of other nutrients are not recommended and should be consumed sparingly or not at all. These include carbonated and non-carbonated beverages, such as regular sodas and fruit drinks, usually sweetened with high-fructose corn syrup or sucrose. These caloric sweeteners, which provide hidden calories in beverages, have been linked to dental caries, excess energy intake, weight gain, and type 2 diabetes.

How Much of Each Beverage Should You Consume?

Most adults with an energy requirement of 2,200 kcal per day need to drink about 100 fl oz (3 liters) of beverages. At most, 10% of the daily total calories should come from beverages. Based on this reasoning, we generally recommend the following daily amounts of the different beverages:

  • Water, 20-50 fl oz (but can be up to the full daily beverage intake of about 100 fl oz)
  • Tea and coffee (unsweetened, no or little milk or cream added), 0-40 fl oz
  • Low-fat or skim milk and soy beverages, 0-16 fl oz
  • Noncalorically sweetened beverages, 0-32 fl oz
  • Caloric beverages with some nutrients: 100% fruit or vegetable juices, 0-8 fl oz; whole milk, 0 fl oz; sports drinks, 0-8 fl oz; alcoholic beverages, 0-1 drink for women and 0-2 drinks for men
  • Calorically sweetened beverages, 0-8 fl oz

What Can the Food Industry and Government Do?

While self-policing in the beverage industry is unlikely, manufacturers can reduce calories in all beverages. To encourage more healthful choices, government could tax added sugar in all beverages so that the relative cost of most calorically sweetened beverages increases greatly. However, it is not known if this would achieve the desired result of reducing energy intake. Reducing or eliminating advertisements for these products would also help, especially to young children and adolescents, as would health education programs in schools.

Last updated November, 2006