

Food as Medicine - Dietary Supplements

DK Publishing logoDK Publishing 2/07/2014 DKBooks
Photo: Supplements for health - In the last decade, public interest in the benefits of supplements has increased and sales have skyrocketed. © Provided by DKBooks Supplements for health - In the last decade, public interest in the benefits of supplements has increased and sales have skyrocketed.


Photo: Taking a supplement - You may need to take a vitamin or mineral supplement for various reasons, including pregnancy or illness. © Provided by DKBooks Taking a supplement - You may need to take a vitamin or mineral supplement for various reasons, including pregnancy or illness.


Dietary Supplements

Vitamin and mineral supplements can improve your health.

Public interest in vitamins and minerals for health has never been higher. Evidence continues to grow that certain supplements can improve health and possibly even prevent cardiovascular disease, cancer, and the bone disorder osteoporosis.

According to recent surveys, 18–40 percent of North Americans report that they take vitamin and mineral supplements as part of their routine health regime. In the US between 1994 and 2000, sales of supplements grew by nearly 80 percent, from $8.8 billion to an estimated $15.7 billion. In this section, we review the most popular vitamin and mineral supplements and tell you who may benefit from taking them and any precautions to be noted.

Safety of supplements

In 1990, the Nutrition Labeling and Education Act was passed in the US. This law means that the Food and Drug Administration (FDA) has to approve the safety and health claims made about supplements by the manufacturer before they can be marketed. Unlike medications, which are rigorously tested and their manufacturing processes monitored, the FDA does not examine the purity of supplements or determine their medical effectiveness. However, the FDA can prevent the sale of a supplement if they have proof that it is unsafe for consumption.

Manufacturers are allowed to make general health claims about their products as long as they do not contain reference to preventing or curing a specific disease.

Types of supplements

In 1994, the Dietary Supplement Health and Education Act (DSHEA) was passed in the US, defining a dietary supplement as a product that is taken orally and contains a dietary ingredient, such as a vitamin or a mineral. Other ingredients include herbs, botanicals, amino acids, enzymes, and fish oils. They can be extracts or concentrates of the particular ingredient and may be available as capsules, tablets, gel caps, liquids, or powders.

Buyer beware

Despite the form of the supplement, the DSHEA classifies supplements under the category of food, not medication, and it is important for companies to label their products accordingly. Unfortunately, this gives rise to a situation in which the buyer is at risk of purchasing supplements that have absolutely no benefit, such as shark cartilage, or that are potentially harmful, such as the herb ephedra.

Chelated minerals

Minerals in supplements are often bound—or chelated—to another substance in order to improve their absorption and use by the body. Chelated minerals are also better tolerated and may be less harmful to the body than pure forms.

Substances to which a mineral can be chelated include amino acids, gluconates, citrates, and picolinates. If you read the labels on supplements, you will see different forms of minerals. For example, zinc as zinc picolinate, magnesium as magnesium oxide, iron as ferrous fumarate, and calcium as calcium carbonate.

Manufacturers of supplements choose a certain form of a mineral, depending on digestive factors and how well the intestine tolerates it.

Can you benefit from supplements?

A general multivitamin may provide some nutritional “insurance” against missing specific nutrients due to lack of variety in your diet or to make sure you get enough nutrients when you need extra, such as during pregnancy.

However, nutritionists are still trying to demonstrate a specific benefit for supplements with regard to prevention and treatment of chronic diseases. The use of vitamins and minerals in this way is different from correcting “classic” vitamin deficiencies, which are rare in North America. However, vitamin sales continue to climb and are a $15-billion-a-year business in the US.

No proven benefits

The efficacy of vitamin E for treating and preventing cardiovascular disease has been studied for over 30 years, and tested in people with or at risk for the disease. However, it has not been shown to be effective, and recent trials have shown that it may even have a negative impact on cardiovascular health.

Chromium is needed by the body to process the hormone insulin and control levels of glucose in the blood, but supplements do not seem to help people with or at risk of developing diabetes. Beta-carotene is effective at blocking steps in cancer development when tested on cells in the laboratory, but when given to people at high risk of cancer it appears to have no effect.

Get professional advice

People who want to supplement their diet with any form of nutrient should consult a health-care professional. He or she can provide advice on which supplements you should or should not take if you have a preexisting disorder or are taking certain medications.

A general multivitamin and mineral supplement may be helpful as long as the contents are at the correct Dietary Reference Intake levels. Data is lacking to support the benefits of taking isolated supplements of single nutrients or combinations, such as the antioxidant vitamins C and E, carotenes, and selenium. The charts show who would benefit from taking specific supplements. In fact, the body actually absorbs vitamins in food more easily than from supplements.

Can you take too much?

Harmful effects of vitamins and minerals usually result from taking too much, misusing supplements, or dosage errors. If you are taking large doses of vitamins or minerals, your doctor should be closely monitoring you. The fat-soluble vitamins—vitamins A, D, E, and K—are stored in the liver, and if they are taken in excess may build up to harmful levels more quickly compared to the water-soluble vitamins—the B vitamins and vitamin C .


Several of the vitamins can be harmful in excess. Too much vitamin A leads to cracked lips, headaches, blurred vision, and dry rough skin. Too much vitamin D causes poor appetite, nausea, vomiting, and deposits of calcium in body tissues. Large doses of B-complex vitamins can produce symptoms ranging from itching, flushing, nausea, lightheadedness, or tingling sensations in the fingers to progressive loss of balance and sensation in the legs. Symptoms usually disappear when the offending vitamin is withdrawn. Excessive doses of vitamin C can cause diarrhea and have also been reported to predispose those susceptible to oxalate kidney stones .


Many minerals taken in excess can be harmful. In children, excessive intake of iron is dangerous and too much fluoride turns the teeth brown. People treated for ulcers may develop milk–alkali syndrome, due to excessive intake of calcium from medication, causing muscle pain and weakness. Excessive intake of vitamin D can cause overabsorption of calcium, and excessive zinc may suppress the immune system and interfere with the absorption of copper.

If you do take a supplement, select a sensible one with the levels of nutrients recognized as safe and avoid going over the tolerable upper limit.

Jargon buster

Tolerable upper intake level (UL)

This indicates the maximum safe amount of a nutrient to eat or take as a supplement without risk of side effects from poisoning. ULs have been determined for many of the vitamins and minerals, including the vitamins A, B6, folate, C, D, and E and the minerals calcium, copper, zinc, magnesium, and selenium.

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