Does Vitamin D3 Have Vitamin A In It?

By definition, vitamins are essential organic substances that are not produced within the body in significant amounts. Vitamin D-3 is an exception to that rule because it can be produced within the skin in response to sunshine in sufficient amounts. Vitamin A is acquired from dietary sources only and is not involved in the production of D-3, although both vitamins are found in some of the same foods. Although vitamins D-3 and A are mutually exclusive substances, they are both required for strong immunity.

Vitamin D-3

Vitamin D is a collective term for five fat-soluble substances, called secosteroids, which are essential for strong bones and immunity, among other important functions. Vitamin D-3, or cholecalciferol, is especially important for human biochemistry as it acts much like a hormone. Vitamin D-3 is synthesized within the skin when 7-dehydrocholesterol reacts to ultraviolet-B radiation at wavelengths between 270 and 300 nm, as cited in "Biochemistry of Human Nutrition." According to the National Institutes of Health, 400 IU per day of vitamin D is adequate for infants, whereas most adults require 600 IU and those older than 70 need 800 IU. Some health professionals believe these levels are too low and point out that thousands of IU of D-3 can be produced hourly within the skin under ideal sun conditions. Fear of skin cancer, indoor lifestyles and use of sunscreens has led to widespread deficiency in the United States.

Vitamin D-3 Food Sources

Although the sun is the best source of D-3, it is also found within certain foods. According to the "American Dietetic Association Complete Food and Nutrition Guide," the best food source of vitamin D-3 is fish, especially the flesh of salmon, mackerel, cod, sardines and tuna. Fish liver oils, beef liver, shrimp and egg yolks are other very good sources. In the United States, milk has been fortified with vitamin D since the 1930s in efforts to reduce childhood rickets. Breakfast cereals often contain added vitamin D, as do many brands of orange juice, yogurt and margarine. D-3 is not the most common type of vitamin D used to fortify foods; D-2 is much more common.

Vitamin A

Vitamin A is also a fat-soluble substance, meaning that is requires fats within the digestive tract to be absorbed. Vitamin A enhances immunity by forming and maintaining moist mucous membranes that line the eyes, nose, mouth, sinuses, lungs and digestive system. These physical barriers trap and eliminate debris, toxins and potential pathogens. Vitamin A is also a powerful antioxidant and eliminates free-radicals that can cause inflammatory reactions and tissue deterioration. Further, vitamin A is required for the production of rhodopsin, a light-sensitive pigment in the retina needed to detect shades of gray in low-light conditions. The National Health Institutes states the recommended daily amounts of vitamin A range from 300 mcg for infants to 900 mcg for men, to 1,300 mcg for lactating females. Reduced immune function is one consequence of both vitamin A and D deficiencies.

Vitamin A Food Sources

Vitamin A can be consumed as retinol or as beta-carotene, which is converted to retinol in the liver and stored there. Rich sources of retinol are similar to those of vitamin D-3 and include pig, beef and fish livers, eggs, some cheeses and fortified dairy products, as cited in the "American Dietetic Association Complete Food and Nutrition Guide." Foods rich in beta-carotene include fleshy orange vegetables, such as carrots and sweet potatoes. Because vitamin A is stored in the body, high levels can lead to toxicity, which is not the case with D-3.