How Much is Too Much?

Excess Vitamins and Minerals in Food Can Harm Kids’ Health

June 19, 2014

How Much is Too Much? : Sources of Added Vitamins and Minerals in Children’s Food

Vitamin A, zinc and niacin all occur naturally. They are also added to foods that young children eat regularly

Table 3: Sources of added vitamin A, zinc and niacin in the diets of 2-to-8-year-old children

Food

Percent contribution

Preformed Vitamin A

Ready-to-eat cereal

42.6%

Milk

25.1%

Milk drinks

11.7%

Pasta dishes

3.5%

Margarine, butter

3.1%

Niacin

Ready-to-eat cereal

51.6%

Yeast bread, rolls

10.4%

Pizza

6.9%

Pasta dishes

5.1%

Cakes and cookies

4.8%

Zinc

Ready-to-eat cereal

96.8%

Source: National Health and Nutrition Examination Survey 2003-2006, Berner 2014

Vitamin A is the common name for a group of fat-soluble substances present in two forms in food: preformed vitamin A (retinol and retinyl esters such as retinyl palmitate and retinyl acetate) and vitamin A precursor carotenoids (beta-carotene, alpha-carotene, and many others) that the body converts into retinol or retinoic acid. Vitamin A precursors are also called provitamin A. Different chemical forms of vitamin A play specific roles in the body. Retinol is important for eyesight. Retinoic acid supports normal body growth and development and plays a critical role in the formation and maintenance of organs and tissues. Retinoic acid is also a key regulator of numerous growth and metabolic processes. 
 
Preformed vitamin A such as retinyl palmitate is rapidly converted first to retinol and then to retinoic acid. Excessive production of retinoic acid caused by ingesting large amounts of preformed vitamin A can disrupt bodily functions and cause overt toxicity. 
 
In contrast, ingesting large amounts of naturally occurring dietary provitamin A carotenoids is not associated with toxicity. That’s because it takes multiple metabolic reactions to convert provitamin A precursors into retinol, generating relatively small amounts of both retinol and retinoic acid. Retinol has 12 times the activity of beta-carotene and 24 times the activity of alpha-carotene. 
 
Preformed vitamin A occurs naturally in dairy products, eggs, fish and meat, especially liver. Carotenoids are found in bright yellow and orange vegetables such as carrots, pumpkin and sweet potatoes, broccoli and spinach. Preformed vitamin A, either as retinyl palmitate (most common) or retinyl acetate, is frequently added to milk and milk-based drinks, butter spreads, cereals, snack bars, cookies and cakes. 
 
The FDA has rules regarding vitamin A fortification of butter spreads (margarine) and milk. Butter spreads typically contain 10 percent of the adult Daily Value per serving. Fortified milk can contain 10-15 percent of the adult Daily Value per serving. There are no limits on vitamin A fortification of other foods.
 
Niacin, or vitamin B3, encompasses nicotinic acid, niacinamide (also called nicotinamide or nicotinic acid amide) and their derivatives. Niacin occurs naturally in foods such as meat, fish, sunflower seeds and peanuts, as well as in whole grains such as whole wheat and brown rice. The liver can also synthesize niacin from the amino acid tryptophan, a building block for proteins.
 
The Institute of Medicine concluded in 1998 that niacin intake in the United States is “generous” (IOM 1998). Nevertheless, food producers enrich a variety of foods with additional niacin (often in the form of niacinamide), including cereals, breads and flour-based dishes such as pizzas and cakes. While there is no evidence of harm from naturally occurring niacin, excess niacin in fortified foods or supplements has been linked to harmful effects.
 
The FDA requires the addition of certain micronutrients to processed grain foods such as breads, corn meal, flour, macaroni and rice to compensate for the loss of these nutrients during flour bleaching and processing. The typical micronutrients added to enrich cereal grains are thiamin, riboflavin, niacin, iron and folic acid (Yamini 2012). For niacin, the legally required enrichment amount is 15-34 mg/pound, which provides 8-15 percent of the adult Daily Value per serving, depending on the food. Breakfast cereals are often fortified to much higher levels, up to 100 percent of the adult Daily Value.

Zinc is an essential mineral. It is naturally present in many foods, including milk and meat products as well as grain-based products. It is a component of dietary supplements as well as cold lozenges and some over-the-counter cold remedies. Breakfast cereals are the number one source of added zinc in the diets of children. The FDA does not limit the amount of zinc added to fortified foods.