Dietary Guidelines May Produce Unintended Health Consequences

The 2010 U.S. Dept. of Agriculture Dietary Guidelines are now public. This 445-page document has many implications for the food industry, national nutrition policy, and consumers. Aside from the obvious major action items that surround the primary issue (obesity), the modeling exercises by the Dietary Guidelines Advisory Committee revealed many possible unintentional consequences. In the absence of monitoring the American population with respect to nutrients of concern, compliance with the guidelines could pose additional public health challenges.

Within the Nutrient Adequacy section, the report notes several food groups and dietary components that are underconsumed and may be low enough to be of concern. These include vegetables, fruits, whole grains, milk and milk products, and oils. Despite the recommendations presented in the 2005 Dietary Guidelines, scientific evidence indicates that Americans still do not consume adequate amounts of these products. For example, among adults over the age of 50, 75% to 90% do not meet the recommended intake of 2.5–3 cup equivalents of dairy products daily.

Even more compelling are the whole grain consumption data, which indicate that more than 95% of the population fails to meet minimum requirements. Consistent with these observations is consumption of dietary fiber; an even greater percentage of the population fails to meet the fundamental requirement of 14 g/1,000 calories. Milk products, which contain high quality protein, calcium, potassium, vitamin D, and vitamin A, are not consumed at recommended levels. Evidence indicates that at-risk populations, such as growing children, consume only about 25% of the recommended amount of milk.

Similarly, even the intake of meat, poultry, fish, eggs, soy products, nuts, and seeds is below recommended amounts among many females. These foods are nutrient-rich in protein, heart- and brain-friendly fatty acids, vitamins, and other important nutrients.

As one would expect, the consequences of such under-consumption also represent a shortfall of numerous nutrients, including vitamins A, C, D, E, K, and choline, as well as calcium, magnesium, potassium, and dietary fiber. One could attribute the low levels of vitamins A and C, and the other fat-soluble vitamins to low intake of vegetables and fruit. Of course, low intake of vitamin D and calcium may also reflect, in part, insufficient milk intake, while a poor vitamin D status may also be a sign of insufficient exposure to sunlight.

Considering the dietary goal of limiting saturated fatty acid intake to 7% of total calories, and assuming dietary stearic acid is neutral relative to cardiovascular risk, as well as limiting dietary cholesterol to less than 200 mg (particularly among those at risk of heart disease and type 2 diabetes), one of the shortfall nutrients is choline. Eggs (~125 mg/fresh egg with yolk) are a primary source of dietary choline. If eggs are restricted to four per week (to minimize saturated fat and cholesterol), the daily intake of choline (~450-500 mg/day) may not be achieved. Inclusion of other choline sources, such as meat, poultry, and some starchy vegetables such as potatoes is critical. Hence, this is one of the unintended consequences that deserve further research.

The Dietary Guidelines also pose challenges in terms of the agricultural supply chain. A 2006 report from USDA’s Economic Research Service (based on 2002 data) indicates that an additional 8.9 million acres of cropland are necessary to support the guidelines’ vegetable intake recommendation, and about 4.1 million more acres are needed to produce the advised fruit consumption. Independent modeling suggests that by 2015 an additional 10.3 million acres of cropland will be necessary to meet vegetable production needs and an additional 4.7 million acres for fruit production. Thus, total harvestable cropland would need to increase by about 3%, or nearly 320 million acres, a level equivalent to 1997 acreage. Equally challenging is the production of fluid milk and milk products. The 2002 data suggest an increase of 107.7 billion pounds is needed, equivalent to a 66% increase in the number of dairy cows, feed grains, and grazing acreage. To meet 2015 expectations, a more appropriate increase is nearly 80%.

The term “aspirational” has been ascribed to the new dietary guidelines. This term is applicable to consumer compliance, food industry challenges, public health policy harmonization, and agricultural practices. It is, therefore, incumbent that all stakeholders, including nutrition educators, food scientists, dietitians and nutritionists, government agencies, farmers, environmental advocates, and public health policy makers, collaborate in developing a strategic plan for successfully implementing the new Dietary Guidelines and reducing the risk of unintended consequences.

Roger Clemens, Dr.P.H.,
Contributing Editor
Chief Scientific Officer, ETHorn, La Mirada, Calif. 
[email protected]