Evaluation of vitamin A toxicity

Article Abstract:

Vitamin A is a fat-soluble vitamin that is stored in the body. Because vitamin A is stored, excessively high intakes can lead to a toxic accumulation of the vitamin. It is important to discover what level of intake constitutes the maximum safe level, above which toxicity will generally result. This article discusses the data available on toxicity in children, adults, and pregnant women. Symptoms of vitamin A toxicity in adults include loss of appetite, blurred vision, abdominal pain, drowsiness, headache, nausea, and irritability. Because it is often difficult to obtain accurate descriptions of people's diets, much of the information on intakes is based upon the amount of vitamin A supplements consumed. Intakes of 25,000 to 50,000 international units (IU) daily for several months or longer have caused toxicity. Lower intakes can be toxic in persons who have viral hepatitis, reduced liver function caused by drug therapy, or malnutrition. Children and pregnant women are also particularly vulnerable. Toxicity occurs in children at vitamin A intakes as low as 1,500 IU per kilogram body weight daily. While the maximum safe level of intake in pregnancy is not yet known, birth defects have been linked to maternal intakes as low as 25,000 IU per day. It should be noted that there are several different forms of vitamin A, and beta-carotene has much lower toxicity than retinol. It is not possible to define a maximum safe level of vitamin A intake with certainty at this time, but it appears that keeping under 10,000 IU/day will avoid toxicity in most people and is generous for meeting nutritional needs. However, vulnerable individuals may suffer toxic effects even at intakes of 10,000 IU/day, and it appears preferable to consume no more than the Recommended Dietary Allowance (RDA), which is 5,000 IU per day for most adults. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Reports, Birth defects, Vitamins

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Carbohydrate and lipid metabolism in patients with non-insulin-dependent diabetes mellitus: effects of a low-fat, high-carbohydrate diet vs a diet high in monounsaturated fatty acids

Article Abstract:

A diet rich in carbohydrates and soluble fiber and low in saturated fat is prescribed for patients with non-insulin-dependent diabetes mellitus (NIDDM). This diet is designed to improve blood glucose (sugar) control, reduce the amount of low-density-lipoprotein (LDL) cholesterol in the blood, and reduce the risk of developing heart disease. Other studies have reported that diets low in saturated fat and rich in polyunsaturated or monounsaturated fat reduce the risk of heart disease. Therefore, a study was performed to compare two diets, one rich in complex carbohydrates and one rich in monounsaturated fat. The subjects included 19 patients with NIDDM who had good control over their blood glucose levels and were not taking insulin. The study was broken down into three phases. For the first two months, all of the subjects followed diets high in carbohydrate and low in fat (carbo diet). During the second two months of the study, all of the subjects followed diets rich in monounsaturated fat (mono diet). For the next two-month period, the all subjects returned to the carbo diet. Blood glucose and cholesterol levels were measured before and after each diet period. Blood glucose and cholesterol levels were the same at the end of each diet period as they were at the beginning of the study. Also, there were no changes in blood triglyceride (fatty acids) levels or high-density-lipoprotein, the beneficial form of cholesterol, during the three diet periods. It is concluded that both diets are well tolerated and do not alter blood glucose or cholesterol levels. This suggests that patients with NIDDM may be able to consume a wider variety of foods without suffering adverse side effects. (Consumer Summary produced by Reliance Medical Information, Inc.)

Care and treatment, Physiological aspects, Type 2 diabetes, Dietary fat, Blood cholesterol, Diet therapy, High-carbohydrate diet, High carbohydrate diet

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Serum vitamin A and retinol-binding protein in patients with insulin- dependent diabetes mellitus

Article Abstract:

Recent research reports have demonstrated that insulin-dependent diabetics (type-I) have lower blood levels of Vitamin A than normal control patients. Studies have shown that, in animals made experimentally diabetic, injections of insulin caused lowering of stored vitamin A in the liver. The skin of diabetic patients often appears colored by carotene which is suggestive that ingested carotene (the normal dietary source of Vitamin A) is not converted to Vitamin A. The current study included 25 patients with insulin dependent diabetes mellitus and 25 nondiabetic volunteers. The subjects fasted overnight and blood samples were collected. The level of retinol-binding protein (the carrier of Vitamin A) was also measured in both diabetic and normal subjects. The data demonstrated that blood concentrations of both retinol-binding protein and Vitamin A were reduced in blood concentration in the diabetic patients when compared with the normal volunteers. There was also a correlation in both groups between the quantity of retinol-binding protein and Vitamin A, but no significant difference (as expected) in the level of Vitamin E. This experiment suggests that insulin treated diabetic patients have reduced levels of circulating Vitamin A, perhaps as a result of decreased liver vitamin A mobilization.

Research, Complications and side effects, Diabetes, Vitamin E, Insulin, Diabetes research, Vitamin A deficiency

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