Nausea, polyuria and diarrhoea are early symptoms of toxicity of vitamin D. Later symptoms include weakness, the deposition of calcium in soft tissues and depression. It is claimed that very high intakes of vitamin C (a gram or more a day) can cause diarrhoea, kidney stones in sensitive people, and precipitate the deficiency disease scurvy if the high dose is stopped.
Large doses of vitamin E prevent vitamin K from clotting blood correctly. Large doses of calcium limit the absorption of iron.
Chronic vitamin A intoxication occurs more frequently in children than adults. Depending on the severity of the intoxication, children may develop loss of appetite, weight loss, irritability, fissuring at the corners of the mouth, and cracking and bleeding of the lips. Later signs include liver enlargement, loss of hair and severe bone and joint pains.
More than 50% of Americans over the age of 55 believe taking a multivitamin once a day will reduce their risk of cancer. clinicians. Whilst there is strong evidence to suggest that the vitamins and nutrients found in fruit, vegetables and whole grains are vital in helping the body defend itself from malignant cells (more than 190 scientific studies have been able to demonstrate the benefits of a diet rich in plant foods), only a handful have found favour in dietary supplements.