A longitudinal study of the relationship between vitamin A supplementation and plasma retinol, retinyl esters, and liver enzyme activities in a healthy elderly population
Vitamin A plays an important role in the growth and development of the skin, nervous system and bone, and it is essential for maintaining good vision. A deficiency of vitamin A can cause growth retardation, dry skin (xeroderma) and night blindness. On the other hand, excessive intake of vitamin A (hypervitaminosis) can be toxic to the liver and can cause symptoms of headache, dizziness, nausea, flaky skin, and bone pain. The recommended daily dietary allowance (RDA) of vitamin A for adults is 5,000 IU for men and 4,000 IU for women. However, many elderly people take over-the-counter supplements that contain five times the RDA of vitamin A. Hypervitaminosis A has been reported to cause high levels of retinyl ester to appear in the blood. It has been suggested that measuring the amount of retinyl ester in the blood may be a useful predictor of vitamin A toxicity. Therefore, a study was performed to determine whether the amount of retinyl ester in the blood is related to the amount of vitamin A taken, whether retinyl ester accumulates in the blood over time, and whether long-term intake of high doses of vitamin A causes liver damage. The study included 116 healthy elderly people (ages 64 to 88). The subjects were divided into three groups based on the amount of vitamin A supplement taken: less than 5,000 IU, 5,001 to 10,000 IU, or greater than 10,000 IU per day. In addition to the vitamin A supplements, the amount of vitamin A in the diet ranged from 2,528 to 23,032 IU per day. Blood levels of retinyl ester and liver function were evaluated over a five-year study period. Blood levels of retinyl ester were highest in the subjects who consumed the largest amounts of vitamin A, but the amount of retinyl ester in the blood did not increase over time, regardless of the amount of vitamin A taken. In this study, long-term use of high doses of vitamin A did not cause liver toxicity. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Clinical Nutrition
The prevalence of cardiovascular risk factors among elderly Chinese Americans
Cardiovascular disease, which affects the heart and blood vessels, is a major health problem among the elderly. Stroke is the most common cause of cardiovascular disease among elderly Chinese persons. Death due to stroke and myocardial infarction (heart attack) was estimated in 1976 at 138.7 and 29.6 per 100,000 Chinese, respectively, as compared with 87.9 and 301.0 per 100,000 Americans, respectively. Although the Chinese make up one quarter of the world's population, little is known about the various characteristics that may influence their risk of cardiovascular disease. The nutrition and health of 346 Chinese immigrants aged 60 to 96 years were assessed to determine cardiovascular risk factors. The elderly Chinese were physically active, rarely obese, and consumed a diet high in carbohydrate and low in fat and vitamin C. Thirty-nine percent of the men smoked cigarettes while few women did, and alcohol consumption was rare among both men and women. The elderly Chinese had lower blood pressures and levels of total, low-density lipoprotein, and high-density lipoprotein cholesterol, and ascorbic acid (vitamin C), as compared with elderly Americans. This group of Chinese immigrants was similar in these health measures to the urban population of mainland China, where hemorrhagic (due to bleeding) stroke is the primary cause of cardiovascular death. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Archives of Internal Medicine
Phylloquinone in plasma from elderly and young adults: factors influencing its concentration
Vitamin K has important roles in the body involving blood clotting and synthesis of proteins found in the liver, kidney, bones, skin, and reproductive organs. Accurate methods for measuring the concentration of vitamin K (phylloquinone) in the blood have just recently been developed. Prior to this study, little research had been done concerning the normal level of vitamin K in the human body. A group of 131 young and 195 elderly men and women was tested and a normal range of values was developed that can be used in the future when testing for deficiency of the vitamin. In this group, vitamin K levels differed by sex and age, and showed seasonal variation. Young women had lower vitamin K concentrations than elderly women, but for men the reverse was true. Circulating vitamin K was higher when blood levels of vitamin E and triglycerides were higher. When blood vitamin K was expressed per unit of blood triglycerides, elderly subjects had lower vitamin K values on average than young subjects. Diet records were kept by the participants, but as the vitamin K content of many foods is not known it was not possible to calculate the amount of vitamin K consumed by the study participants.
Publication Name: American Journal of Clinical Nutrition
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