Featured Topic

• Recommendations
• Nutrition and Performance
• Summary
• Vitamins and Minerals
• Gaps in Knowledge
• Conclusions
• Recommendations
• Dietary Guidelines for Americans 2005

Vitamin and Mineral Supplements
Brian Sharkey, Ph.D., MTDC; Carla Cox, Ph.D., R.D., University of Montana; and David Cone, M.D., Yale University.

Since the 1960s, MTDC and the University of Montana Human Performance Laboratory have evaluated the energy and nutrition needs of wildland firefighters. Field studies consistently show a high level of energy expenditure. Energy needs average about 7.5 kilocalories per minute, more than 400 kilocalories per hour. In 1998, Drs. Brent Ruby and Brian Sharkey studied firefighter total energy expenditure during 5 days of wildland fire suppression.

Using sophisticated doubly labeled water techniques, they found that the energy expenditures ranged up to and beyond 6,000 kilocalories per day. The data showed that firefighters lost total and fat-free weight during the work period, despite the availability of sufficient food in fire camp meals.

Because of those findings, liquid and solid energy supplements have been incorporated into firefighter nutrition. The supplements improve performance, decisionmaking, hydration, and immune function.

High metabolic rates increase the need for micronutrients. Firefighters work in a harsh environment, and are exposed to smoke, heat, cold, sunshine, stress, and exhaustion—conditions that increase oxidative stress and the need for vitamins and minerals.

Nutritional analysis of the food provided to firefighters suggests that energy and micronutrient needs will be met, so long as the firefighter eats enough of the right types of food, including carbohydrate and protein-rich foods, nine or more servings of fruits and vegetables, and several servings of whole grains daily. Some firefighters do not follow this recommendation. This article reviews studies of individuals involved in prolonged work, summarizes recommendations of authoritative organizations, and discusses gaps in current knowledge.

Recommendations

The following organizations have made recommendations for vitamin and mineral supplements based on extensive review of the scientific literature. The summaries below include specific recommendations for those involved in high levels of exertion.

American Dietetic Association: The best nutritional strategy for promoting optimal health and reducing the risk of contracting chronic diseases is to obtain adequate nutrients from a wide variety of foods. Vitamin and mineral supplements are appropriate when well-accepted, peer-reviewed, scientific evidence shows that they are safe and effective.

American Heart Association (AHA): The AHA Dietary Guidelines Revision (2000) says that vitamin and mineral supplements are not a substitute for a balanced and nutritious diet based on fruits, vegetables, and grains. A science advisory published in Circulation (2004) showed that antioxidants (vitamins C, E, and beta carotene) have no effect on preventing or treating cardiovascular diseases.

A recent review of 19 clinical trials, reported at the 2004 meeting of the AHA, indicated that individuals who supplemented their diets with an average of 400 IU (international units) of vitamin E daily had a small but statistically greater risk (10 percent) of dying from any cause, compared to those who did not take the supplement.

American Cancer Society: The society recommends a well-balanced diet and does not recommend the use of vitamin and mineral supplements as a preventive or therapeutic intervention.

American Academy of Family Physicians: The academy states that the decision to provide special dietary intervention or nutrient supplements must be on an individual basis, using the family physician’s best judgment based on evidence of benefit as well as lack of harmful effects. Mega-doses of certain vitamins and minerals have proven harmful.

U.S. Preventive Services Task Force: The task force published recommendations concerning vitamin supplementation to prevent cancer and cardiovascular disease. Task force members conclude that the evidence is insufficient to recommend for or against the use of supplements of vitamins A, C, or E; multivitamins with folic acid; or antioxidant combinations for the prevention of cancer or cardiovascular disease (2003). They recommend that individuals avoid taking take beta carotene to lower the incidence of disease.

Heart Outcomes Prevention Evaluation: In patients at high risk for cardiovascular events, treatment with vitamin E (400 IU daily) for an average of 4.5 years had no apparent effect on their cardiovascular outcomes (New England Journal of Medicine 2000).

Mayo Clinic: Whole foods are the best sources of vitamins and minerals. They offer three main benefits over supplements:

• Whole foods are complex; they contain a variety of micronutrients.
  
  
• Whole foods provide dietary fiber that reduces the risk of cancer, diabetes, and heart disease.
  
  
• Whole foods contain other substances that appear to be important for good health. Fruits contain chemicals that may help protect against cancer, diabetes, heart disease, and hypertension. For more information, visit the Mayo Clinic’s Web site, http://mayoclinic.com.

Summary: These recommendations reflect current scientific data that do not support the use of vitamin and mineral supplements. While studies indicate the value of a diet that includes specific vitamins and minerals, supplementation with specific nutrients does not provide the expected benefit. Supplements are not a substitute for a balanced and nutritious diet. Foods include numerous micronutrients, and their benefits may depend on the mixture, not on the individual nutrient used as a supplement.

Vitamins in food have proven more effective than vitamin supplements.

Nutrition and Performance

The increased energy and nutrient demands of performance in work and sport call for more specific micronutrient recommendations. In 2000, the American College of Sports Medicine, the American Dietetic Association, and the Dietitians of Canada published recommendations for nutrition and athletic performance. They recommend appropriate selection of food and fluids, timing of their intake, and supplemental choices for optimal health and performance. They state:

Athletes will not need vitamin and mineral supplements if adequate energy to maintain body weight is consumed from a variety of foods.

However, supplements may be required by athletes who:

• Restrict energy intake
  
  
• Use severe weight-loss practices
  
  
• Eliminate one or more food groups from their diet
  
  
• Consume high-carbohydrate diets with low micronutrient density

Nutritional performance-enhancing aids should be used with caution, and only after carefully evaluating the product for safety, efficacy, and potency.

American College of Sports Medicine (ACSM): A current comment by the ACSM on vitamin and mineral supplements notes that athletes may be using dietary supplements to gain a competitive advantage. However, athletes should be aware that:

• They should consume a variety of foods rather than nutritional supplements to optimize the vitamins and minerals in their diet.
  
  
• Performance will not be improved if individuals already are consuming nutritionally adequate diets.
  
  
• Only athletes with a defined nutritional deficiency will benefit from supplementation of the nutrient(s).
  
  
• The nutritional adequacy of an individual’s diet should be evaluated by a registered dietician experienced in counseling athletes.
  
  
• Megadoses of vitamins and minerals are not recommended because of the possibility of toxicity and adverse interactions among nutrients.
  
  
• Physically active people who intermittently use vitamin and mineral supplements should use a product that does not exceed the DRI (Dietary Reference Intake) for essential nutrients.

Military Nutrition: The Committee on Military Nutrition Research of the Institute of Medicine’s Food and Nutrition Board has reviewed strategies for sustaining nutrition and immune function in the field (1999). The committee does not recommend vitamin and mineral supplementation of military rations above recommended daily allowance levels. It recommends that, when needed, the preferred method of providing supplemental nutrients is through a ration component. It also recommends that the military gain a better understanding of the prevalence of supplement use and abuse by personnel and make strong recommendations for the use or nonuse of supplements.

Summary

Reputable organizations and scientific studies do not support the use of vitamin and mineral supplements to prevent or reduce the risk of disease. They do recommend a balanced diet using a variety of foods, with emphasis on fruits, vegetables, and whole-grain products.

Athletes will not need vitamin and mineral supplements if their diets provide enough energy to maintain their body weight and come from a variety of sources. Supplements may be required in specific cases. The Committee on Military Nutrition Research does not recommend vitamin and mineral supplements for military personnel whose workloads are similar to those experienced by wildland firefighters.

Vitamins and Minerals

Vitamins: Scientific evidence does not support a performance-enhancing benefit of vitamin supplements in individuals who consume a well-balanced diet. Any improvement in physical performance attributed to the use of vitamin supplements in an adequately nourished individual could be the result of a placebo effect. Vitamins are organic compounds that function as regulators of protein, carbohydrate, and fat metabolism. They are needed to transform the potential energy in food to chemical energy for work. Vitamins are not direct sources of energy.

Vitamins are classified according to their solubility. B-complex vitamins and vitamin C are water soluble. Excess quantities of these vitamins are flushed away in the urine. Large doses of vitamin C can cause adverse effects, such as gastrointestinal disturbances and the formation of kidney stones. Fat-soluble vitamins (A, D, E, and K) are ingested with fats in the diet. Amounts in excess of daily needs are stored in body tissues; megadoses can have adverse effects or become toxic (for example, megadoses of vitamins A and E).

Intense exertion produces compounds called free radicals. These highly reactive compounds can damage muscle tissue and have been associated with heart, cancer, and vision problems. The so-called antioxidants—vitamins C, E, and beta carotene, along with the minerals selenium and zinc—may protect against some effects of reactive oxidative radicals.

Related Studies: Recently, the use of antioxidant vitamins has been suggested to promote health and enhance performance. Long- or short-term supplementation with these vitamins has no effect on submaximal performance, aerobic capacity, or muscle strength. Evans (American Journal of Clinical Nutrition, 2000) recommended vitamins E and C for endurance athletes to protect them from oxidative stress and reduce the rate of lipid oxidation, that could be associated with the risk of heart disease.

The results of studies of vitamin C and E in endurance athletes have been inconclusive or negative. Vitamin C supplements failed to reduce exercise-induced oxidative stress and decreases in immune function during an ultramarathon (Nieman and others, Journal of Applied Physiology, 2002). Two months of vitamin C (1,000 milligrams daily) did not decrease the incidence of upper respiratory tract infections in marathon runners (Himmelstein and others, Journal of Exercise Physiology, 1998). Two months of vitamin E (800 IU daily) were associated with an increase—not a decrease—in lipid oxidation and inflammation during a triathlon. The vitamin E dosage may have been so high it reversed the antioxidant effects (Nieman and others, Medicine and Science in Sports and Exercise, 2004). Additional research is needed to justify vitamin supplementation in endurance athletes.

Minerals: Minerals (such as calcium, iron, zinc, selenium, sodium, potassium, and magnesium) are inorganic elements that act as cofactors for the enzymes that influence all aspects of energy metabolism. They also act as electrolytes in cellular processes. Minerals are not sources of energy. Mineral status may be impaired in individuals who restrict their energy intake during training and performance, or who exclude important food groups.

Performance improves when mineral deficits are reduced. High sweat rates lead to the loss of some minerals. Mineral supplements, especially in those with adequate nutrition, can have detrimental effects, ranging from gastric upset to a copper deficiency and reduced levels of HDL (good) cholesterol (caused by zinc supplements). High doses of some vitamins and minerals can lead to neurological damage and may interfere with the absorption of other nutrients.

Zinc may subtly reduce cold symptoms. Iron is prescribed for those with verified iron deficiency, and calcium is used by those at risk for osteoporosis (loss of bone density). High consumption of cola drinks increases the risk of osteoporosis. The sodium and potassium lost in sweat during work in the heat can be replaced during meals, when snacking, and when drinking carbohydrate/electrolyte beverages. Salt tablets that are sometimes used to replace sodium can cause gastrointestinal distress and elevate blood pressure.

Gaps in Knowledge

Recommendations on vitamin and mineral supplements that are appropriate for the general population do not address the concerns of wildland firefighters. Recommendations for endurance athletes are more specific in regard to high energy expenditures during training and performance. Military nutrition recommendations are most specific in regard to energy requirements, environmental conditions, and stress. However, there is limited information on which to base a recommendation for vitamin and mineral supplements for wildland firefighters.

While we know the energy and nutrient content of fire camp meals, we do not know the extent to which firefighters select and eat foods that meet nutritional guidelines. Failure to meet guidelines may be tolerable during short deployments, but over a full season of work, nutritional deficits could lead to decreases in work performance, reduced immune function, and possible illness. Field studies could provide information concerning nutrient intake and the need for wildland firefighters to receive vitamin and mineral supplements.

Conclusions

The increased energy and nutrient demands of wildland firefighting should be met by a balanced diet based on a variety of foods, including carbohydrate and protein-rich foods, nine or more servings of fruits and vegetables, and several servings of whole grains daily.

Firefighters who are unable or unwilling to include a wide variety of foods from all the food groups could consider a multiple vitamin and mineral supplement, not to exceed the DRI. Doses that exceed the DRI should be reviewed by a registered dietician familiar with the individual and the energy demands of the job. High doses of some vitamins and minerals could lead to toxicity and interfere with the absorption of other nutrients. No scientific data or authoritative organizations support nutritional supplements for wildland firefighters.

Recommendations

To assess micronutrient needs of wildland firefighters, the authors recommend:

• Short-term (14-day) and season-long evaluation of firefighter nutritional status. Field studies will provide information concerning energy and nutrient intake and the need for vitamin and mineral supplements. Type I and II firefighters should be included in the analysis.
  
  
• Development of a nutritional guidance program that can be introduced in training and emphasized in fire camps. The program would use printed materials (brochures and posters), Web sites, presentations, and counseling on diets and other information to reach a broad audience.
  
  
• If field data support the need for supplements, they should be incorporated in a ration component (such as an energy bar with antioxidant supplements).

For more information on vitamins and minerals, see the Risk Management and Field Notes sections.