All Issues

Defining “optimal nutrition” has become more complicated with the growing awareness that a healthy diet may reduce the risk of cardiovascular disease, diabetes and other diseases as well as avert nutritional disorders. In contrast to the previous federal government's recommended dietary allowances (RDA), the newer dietary reference intake (DRI) committees are basing nutrient requirements on the contemporary concept of reducing disease risks as well as preventing nutrient deficiencies. Even when USDA food pyramid guidelines are followed, it can be difficult to meet current recommended intakes for essential nutrients. Rather than being rare, marginal nutritional deficiencies in the United States may in fact be quite common. For example, “suboptimal” maternal nutrition can be a significant factor underlying some pregnancy complications such as birth defects, yet a significant proportion of women of child-bearing age do not get sufficient nutrients from their diets. New programs are needed to improve the diets of pregnant women, as well as those of women who are planning pregnancy. In addition to recognized essential micronutrients, if protective dietary phytochemicals are identified, should we try to modify the content of foods, take dietary supplements or simply alter our diets? In the near future, a combination of the three may be the best strategy. Even if new food fortification and supplement policies are promulgated, they should complement, not replace, educational and economic programs designed to improve the public's overall diet.

Young children and elderly people are at great risk of poor nutrition. In a study of low- and high-income young children, we found that a large percentage of both groups, between 24% and 13%, had low intakes of calcium, iron and copper. Interestingly, the high-income children had greater deficiencies of several nutrients than the low-income children. Another study showed that many senior citizens consume diets providing less than two-thirds of the recommended dietary intakes of some essential vitamins and minerals. Further, animal experiments and human studies indicate that nutritional status can influence an individual's susceptibility to environmental toxicants including air pollutants, food contaminants, heavy metals and pesticides. For example, dietary antioxidants are known to aid in the metabolism of organophosphate pesticides; but low-income farmworkers and their children, who are at greater risk of pesticide exposure, often do not consume enough fruits and vegetables with these important nutrients. Likewise, children and adults with iron-deficiency anemia absorb more lead from their environments than those with adequate iron stores. Conversely, good nutrition at all life stages can decrease susceptibility to adverse effects of toxicants. Additional studies on the interactions between diet and chemical exposure in humans will be needed in the future.

Foods provide nutrients such as vitamins, minerals, protein, carbohydrate and fat and a host of other nonessential nutrients that may confer health benefits. Some “nutraceuticals” have been found to boost the immune system, enhance memory function and possibly slow the aging process. For example, flavonoids — which are found in red wine, purple grape juice, green tea and cocoa products — exhibit potent antioxidant activity in laboratory experiments and have been postulated to protect against coronary artery disease and reduce the risk of cancer. Recognizing potential health benefits from flavonoids and other plant extracts, some manufacturers are creating “functional” foods by fortifying, bioengineering and otherwise modifying foods so that they contain higher than normal concentrations of these components. With the exception of echinacea, St. John's wort and Ginkgo biloba, there is a paucity of scientific data for the majority of botanicals sold in health food stores and supermarkets. At the same time, adverse reactions to some botanicals have been documented in humans. Many would argue that government regulation of botanicals is inadequate. Further studies and comprehensive databases are needed to establish the safety and efficacy of popular and widely consumed dietary supplements.

Nutrients exert measurable effects on biological processes and are among many factors that optimize health by helping to prevent, cure, treat or slow the progression of chronic diseases. Certain plant components (i.e., phytochemicals) may not be considered essential by traditional measures, but are increasingly recognized for their beneficial health effects. In particular, dietary flavonoids may make an important contribution to cardiovascular health. Epidemiological studies have shown that intake of flavonoids may be inversely associated with long-term mortality from coronary heart disease in epidemiological studies. Research with flavonoid-rich foods such as red wine, tea, blueberries and chocolate has demonstrated their antioxidant capacity. However, different flavonoids appear to have varying degrees of effect (e.g., inhibiting the oxidation of low-density lipoprotein cholesterol) and most of the flavonoid research has been limited to a few simple flavonoids, rather than a comprehensive investigation of all flavonoids present in the diet or a particular foodstuff. Well-controlled clinical studies are needed to determine whether flavonoids offer true benefits to cardiovascular health and to understand other potential mechanisms, in addition to antioxidant activity, which may be responsible for their protective action.

Fruits and vegetables are important in a child's diet because they provide the body with vitamins, minerals, fiber and several phytochemicals necessary for growth and development and health maintenance. However, a recent study found that only 7% of children aged 2 to 11 consumed the recommended two servings of fruits and three servings of vegetables each day. A limited number of nutrition education programs have been shown to improve dietary choices and self-reported health knowledge and behavior by school-aged children, at least in short-term results. An innovative approach is needed to motivate children to develop lifelong healthy eating habits. Our research shows that incorporating gardens into the school environment can reinforce nutrition lessons. Likewise, children who plant and harvest their own vegetables are more willing to taste and even like them. California Superintendent of Public Instruction Delaine Eastin has set a goal of “a garden in every school.” As more of the state's farmland is lost to development, garden activities can reinforce good nutrition as well as teach California students about the value of agriculture.

Major challenges confront agriculture and the rural environment as we begin the 21st century: providing for the nutritional needs of a growing human population, and sustaining natural resources for food production and biodiversity. Expanding the land area used for food production accelerates the loss of both animal and plant species, which, in turn, diminishes the genetic diversity available to increase food production. Over the last two centuries, nearly every continent has experienced a colossal loss of animal and plant species due to human intrusions. These losses are accelerating. Beyond the issue of providing adequate food are concerns that continued destruction of tropical forests — and species that survive only in these environments — will contribute to undesirable climatic changes, further complicating agricultural production and biodiversity. Extinction of tropical and other species reduces the world's genetic pool, including potential sources for greater food production and new medicines to improve animal and human health. Competing interests in California for land, water and capital could force agriculture out of California and into areas where the economy and culture are more favorable for food production. Can we assemble the necessary data to make critical decisions about the food systems before irreparable changes preclude reclaiming adequate resources for food production? Large, comprehensive studies are needed of defined agricultural areas, such as the Central Valley. Such studies would be multidisciplinary, long-term and expensive.

In the interest of improving their diet and health, consumers have increased their demand for fresh fruits and vegetables. Meeting this demand has stimulated worldwide trade in fresh produce. Several highly publicized outbreaks of foodborne disease highlight the risks of fresh produce being contaminated during growing, harvesting, processing or transportation. These outbreaks have included domestic as well as imported produce. However, two factors — the challenge of implementing and maintaining good agricultural practices in developing countries, and the potential for produce contamination with exotic microorganisms that can cause foodborne disease — raise special concerns about the safety of imported produce. Investigating outbreaks of foodborne disease can identify new foodborne disease hazards and lead to new strategies to prevent and control them. A strong system of public-health surveillance for foodborne disease provides a foundation for risk management of worldwide food distribution.

Salmonella bacteria continue to be an important public-health problem and have a serious economic impact on the U.S. poultry industry. Although the majority of human infections traceable to Salmonella enteritidis are related to egg consumption, this serotype has also been isolated from a variety of nonegg food items such as meat, vegetables and fish. In Southern California, S. enteritidis phage type 4 infection is the predominant serotype found in human patients. However, the organism has also been found in municipal sewage effluent and in rodent and poultry environments. S. enteritidis phage type 4 was first detected in human patients in Southern California in 1990, but wasn't isolated from food-producing animals until its occurrence at a Southern California egg-layer ranch in 1994. An epidemiological study revealed that the layer flock was infected via effluent originating from a nearby municipal sewage-treatment plant. Human sewage effluent was the primary environmental source, combined with wildlife that further amplified and disseminated the bacteria. This discovery has important implications for understanding the ecology of S. enteritidis infection in poultry and humans and developing appropriate methods to prevent its further spread.

Chlorination of drinking water has eradicated most waterborne disease epidemics. However, small water-supply systems struggle to maintain water quality and aging water-distribution systems are prone to contamination. By the year 2025, California's projected population of 48 million will demand between 1 trillion and 5 trillion gallons per year. Municipal demands clearly will exceed the currently available supply of tap water, forcing conservation and reuse. Future regulations are expected to focus on the quality of the water flowing from the user's tap, rather than the quality exiting the water-treatment facility. As little as 16% of the water treated and conforming to drinking-water health standards is likely to come into direct contact with humans, such as for bathing and drinking. Development of dual water-distribution systems would separate water destined for human consumption from that destined for firefighting, toilet flushing and other domestic uses. As industry manufactures new compounds for drugs, antibiotics, household products and so on, water treatment must be modified to remove or neutralize these new contaminants. Monitoring for new and chlorine-resistant pathogens is also needed.