Gerontologists and nutritionists are now interested in the amount of nutrient that it takes to prevent a chronic disease from occurring rather than the amount of nutrient it takes to prevent a deficiency state from occurring. Insofar as possible, the newly revised RDAs are based on the former rather than the latter. There are increasing data that B vitamins play a role in preventing blood vessel disease; vitamin C and carotenoids play a role in the prevention of chronic eye disease-both cataract and macular degeneration; vitamin D and calcium play a role in the prevention of osteoporosis; and B vitamins play a role in maintaining brain function.

The most widely accepted example of nutrient supplements being of use in preventing chronic disease, is the use of vitamin D and calcium supplements in the prevention of bone mineral loss (1). Vitamin D status diminishes with age due to decreased dietary intakes, decreased vitamin D absorption, decreased sun exposure, decreased skin synthesis of vitamin D, and decreased activity of 25(OH)D 1-alpha hydroxylase. Almost 98% of people over the age of 70 in the STOPIT study were not meeting the new vitamin D RDA, and 95% were not meeting the revised calcium RDA of 1200 mg/day. It is also abundantly clear from several intervention studies that calcium and vitamin D supplements which raise intakes to the recommended levels, result in diminished bone demineralization (2,3,4). Thus, supplementation of the elderly with these two nutrients becomes almost mandatory.

Another strong case for supplementing the elderly can be made for vitamin B12. Atrophic gastritis occurs in approximately 20% of people above the age of 60 (5). The physiologic consequences of atrophic gastritis include changes in gastric emptying and decreased intrinsic factor secretion. However, the stomach has a large reserve capacity for intrinsic factor secretion, and only in the most severe cases of gastric atrophy does intrinsic factor become rate limiting for vitamin B12 absorption. Nevertheless, mild atrophic gastritis also limits the bioavailability of vitamin B12, (6) due to impaired cleavage of vitamin B12 from food protein and peptides as a result of reduced acid pepsin digestion. An additional cause of limited vitamin B12 bioavailability in atrophic gastritis is bacterial overgrowth in the stomach and proximal small bowel, since the bacteria can take up vitamin B12 for their own use (7). Since acid killing of swallowed bacteria is diminished in atrophic gastritis, small intestinal bacterial counts in atrophic gastritis subjects are generally in the range of 105 -108 per mL of small intestinal fluid, whereas in normal elderly the counts are in the range of 102- 103 per mL (8). Although food bound vitamin B12 absorption is impaired in elderly people with atrophic gastritis for the above reasons, crystalline vitamin B12 such as contained in a vitamin pill is unaffected. The new vitamin B12 RDA for adults is 2.4 ug/day for all ages, but for people 51+ it has been recommended by the RDA committee that most of this amount should be obtained "by consuming foods fortified with vitamin B12 or a B12 containing supplement" ( 9).

There is a need for modifying the present food recommendations for the purpose of educating elderly people. This modification should emphasize nutrient dense food choices as well as targeted vitamin and mineral supplementation. For people unable or unwilling to increase their intake of nutrient dense foods, multivitamins and multimineral supplements should be recommended (10 ). The supplement industry should concern itself with the issue of bioavailability of their supplement preparations for the elderly. Also, dosage selections in the preparations should be carefully made, since "more is better" is almost certainly not the case (as has been illustrated by the beta-carotene intervention trials). 

References

1. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine. National Academy Press, Washington, DC.1997.

2.Chapuy MC, Arlot ME, Duboeuf F, Brun J, Crouzet B, Arnaud S, Delmas PD, Meunier PJ. Vitamin D3 and calcium to prevent hip fractures in elderly women. N Engl J Med 1992;327:1637 1642.

3. Prince RL. Diet and the prevention of osteoporotic fractures. N Engl J Med 1997;337:701-702.

4. Dawson-Hughes B, Harris SS, Krall EA, Dallal GE. Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older. N Engl J Med 1997;337:670-676.

5. Krasinski SD, Russell RM, Samloff IM, Jacob RA, Dallal GE, McGandy RB, Hartz SC. Fundic atrophic gastritis in an elderly population: effect on hemoglobin and several serum nutritional indicators. J Am Ger Soc 1986;(34):800-6.

6. King CE, Leibach J, Toskes PP. Clinically significant vitamin B12 deficiency secondary to malabsorption of protein-bound vitamin B12. Digestive Diseases and Sciences 1979;24(5)397 402.

7. Suter PM, Golner BB, Goldin BR, Morrow FD, Russell RM. Reversal of protein-bound vitamin B12 malabsorption with antibiotics in atrophic gastritis. Gastroenterology 1991;101:1039-1045.

 8.Russell RM, Krasinski SD, Samloff IM, Jacob RA, Hartz SC, Brovender SR. Folic acid malabsorption in atrophic gastritis: compensation by bacterial folate synthesis. Gastroenterology 1986;91(6):1476-82.

9. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and its Panel on Folate, Other B Vitamins, and Choline and Subcommittee on Upper Reference Levels of Nutrients. Food and Nutrition Board, Institute of Medicine. National Academy Press, Washington, DC.1998.

10. Russell RM, Rasmussen H, Lichtenstein AH. Modified food guide pyramid for people over 70 years of age. J Nutr 1998;129:751-753.