Vitamins are important for the functioning of the human body. Deficiencies of vitamins can cause adverse effects to health. However, if you are in the habit of using vitamin supplements to address any vitamin deficiency, you may want to stick to the limit prescribed by your healthcare provider.
Too much of anything is not good for health; this is true even with nutrients like vitamins. Let’s examine the recommended intake of certain vitamins and the negative impact to the human body when an individual exceeds the limit.
1. Vitamin A
Vitamin A is a group of fat-soluble vitamins. It is involved in immune function, vision, reproduction, and cellular communication. Optimal amounts of this vitamin can be received through diet. Sources of vitamin A include dairy products, liver, fish, fortified cereals, and vegetables like carrot, broccoli, cantaloupe, and squash.
Recommended Intake: The recommended dietary allowances for vitamin A are given as micrograms (mcg) of retinol activity equivalents (RAE). The recommended intake of vitamin A in adult men is 900 mcg RAE whereas, in adult women, the intake is 700 mcg RAE.1 The tolerable upper intake of vitamin A in adults is 3000 mcg RAE.
Side Effects Of Excessive Vitamin A
Vitamin A is fat-soluble and the body stores the excess vitamins in the liver and the levels may increase with time. Although diets provide vitamin A, the side effects of vitamin A are generally observed when it is taken in the form of supplements. Chronic intakes of excess vitamin A may result in the following:2
- Increased intracranial pressure
- Dizziness
- Nausea
- Headaches
- Skin irritation
- Pain in joints and bones
- Coma
Some studies have reported that over-supplementation of vitamin A may also cause hair loss.3
2. Vitamin C
Vitamin C, also known as ascorbic acid, is a water-soluble nutrient found in foods. They act as antioxidants in the body and fight free radicals that are harmful to the body. Vitamin C also plays a role in the production of collagen – protein that helps maintain the elasticity of the skin and heals wounds. Vitamin C is also important as it helps in the absorption of iron. Some sources of vitamin C include citrus fruits like oranges and tangerine and vegetables like broccoli and tomatoes.
Recommended Intake: The recommended intake of vitamin C for adult men is 90 mg whereas, for adult women, it is 75 mg. People who smoke require 35 mg more than the mentioned recommended intake. The tolerable upper limit of vitamin C in adults is 2000 mg.
Side Effects Of Excessive Vitamin C
People should get most of their vitamin C from the diet. However, some may be used to supplements and this may cause an imbalance, generally, an excess of vitamin C in the body. Taking too much vitamin C can cause the following side effects:4
- Diarrhea
- Nausea
- Stomach cramps
- In individuals suffering from hemochromatosis (a condition that causes the body to store too much iron), excess vitamin C can worsen iron overload and damage tissues
3. Vitamin D
Vitamin D or the sunshine vitamin promotes calcium absorption in the gut and is also important for bone strength and growth. It is also required for immune function and to reduce inflammation. Unfortunately, very few sources of food contain vitamin D. Some sources include flesh of fatty fish such as salmon, tuna, and mackerel and fish liver oils.
Recommended Intake: The recommended intake of vitamin D for adult men and women is the same, that is, 15 mcg. The tolerable upper intake of vitamin D is 100 mcg.
Side Effects Of Excessive Vitamin D
Excessive sun exposure cannot result in vitamin D toxicity. The side effects are experienced because of over-supplementation. The side effects of excessive vitamin D are as follows5
- Anorexia
- Weight loss
- Polyuria
- Heart arrhythmias
- Vascular and tissue calcification due to excess calcium in the blood
4. Vitamin E
Vitamin E is another nutrient that behaves as an antioxidant and fights free radicals that may cause cardiovascular diseases and even cancer. They are available in foods like nuts, seeds, vegetable oils, green leafy vegetables, and fortified cereals.
Recommended Intake: The recommended intake of vitamin E in both adult men and women is 15 mg. The tolerable upper intake of the vitamin is 1000 mg for adults.6
Side Effects Of Excess Vitamin E
Adverse effects of excess vitamin E through supplements have shown that it may cause hemorrhage and interrupt blood coagulation. However, these are reports from animal studies and therefore, more research is required if this applies to humans as well.
5. Vitamin K
Vitamin K is an essential nutrient that supports bone and heart health. It is one of the nutrients essential for bone building and blood clotting. There are two types of vitamin K: vitamin K1 and vitamin K2. The former is found in vegetables especially green leafy vegetables, vegetable oils, and some fruits while the latter is found in dairy products.
Recommended Intake: The recommended intake of vitamin K for adult men is 120 mcg while for women, it is 90 mcg.
Vitamin K may be one of the safest nutrients as the Food and Nutrition Board has not established any side effects from the excess of vitamin K due to its low potential for toxicity.7
Therefore, it is important to provide your body with the essential nutrients through a balanced diet. If there is a need for supplements, make sure you take them under the supervision of a doctor. Do not use supplements without consulting the doctor.
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