Test Your Knowledge

Almost all substances that affect the body (including supplements) can have both positive and negative effects.  

The use of supplements may ensure that people with inadequate nutrition receive adequate amounts of essential nutrients to promote good health and performance.

Many supplements have proven health benefits and may be used to help protect against certain diseases or disorders. For example, the American Heart Association recommends that people at risk of cardiovascular disease take supplements containing omega-3 fatty acids. Calcium supplements can help reduce the risk of osteoporosis in postmenopausal women. Folic acid supplements taken before and during pregnancy may help prevent certain birth defects (e.g., spina bifida). Some evidence suggests that the herb St. John’s Wort may help some people with mild depression.

Supplements may also be used to correct deficiency diseases, such as anemia (iron deficiency), pellagra (niacin deficiency) and beriberi (thiamine deficiency), goiter (iodine deficiency) and scurvy (vitamin C deficiency).

Research continues to discover potential new benefits of many supplements. For example, one recent study found that people who take folic acid supplements may retain more of their ability to hear low-frequency sounds as they get older. Another study found children may have improved hand-eye coordination if their mothers take fish oil supplements during pregnancy.

In contrast, some other studies have failed to confirm claims made for supplements. Recent research indicates that taking calcium supplements during childhood probably does not reduce the risk of aging-related fractures later in life.  

It is important to note that these findings have not yet been confirmed by broader research.

Supplements have limits. They cannot:

• Replace prescription medication
  
  
• Treat or cure diseases or medical conditions (e.g., high blood pressure)
  
  

• Make up for a poor diet or bad habits (e.g., smoking, physical inactivity)
  
  

• Work miracles (e.g., promote weight loss without exercise or reducing calories)

Supplements may also interact with prescription or over-the-counter drugs, other supplements, and even components of conventional foods or beverages. Side effects may range from bothersome to deadly. Supplements may also interfere with surgery or recovery from surgery (e.g., ginseng). Certain supplements may not be appropriate for people with certain diseases or medical conditions. For example, vitamin C is not recommended for people with hemochromatosis because it may contribute to iron accumulation in people with this condition. Likewise, ginseng may adversely affect blood sugar levels in patients with diabetes.  

Examples of possible supplement interactions include:

Almost any nutrient (including supplements) can be toxic if taken in large quantities. Excess amounts of certain supplements may lead to the following:

It is unclear what levels of certain supplements, especially herbs or other botanical products, are safe. For many, it is not known at what point some dietary ingredients become excessive and can lead to negative effects on a person’s health. It is important to read any warnings on the label regarding supplement use. However, manufacturers are not required to list warnings on the label, so consumers are advised to contact the manufacturer for information about any possible warnings or side effects of their product.

Herbal dietary ingredients that may pose serious health problems include:

• Aristolochic acid. A potential carcinogen that can cause permanent kidney damage.
  
  
• Chaparral. May cause sudden, irreversible liver and kidney damage.
  
  
• Comfrey. A possible carcinogen that may cause liver damage.
  
  
• Ephedrine/ephedra sinica/epitonin. A stimulant that can be especially dangerous when mixed with other stimulants (e.g., caffeinated products). Possible effects range from nervousness to seizures, heart attack and death.
  
  
• Lobelia. Particularly dangerous to people with heart disease, it may cause breathing problems, low blood pressure and death.
  
  
• Germander. May cause liver disease and death.
  
  
• Magnolia-stephania preparation. May lead to kidney failure.
  
  
• Willow bark. This herb has chemical components (salicylates) that can have similar effects to aspirin. Potential adverse effects include Reye syndrome (fast-acting and potentially fatal disease in children under 18 associated with aspirin use following a viral infection) and possible allergic reactions.
  
  
• Wormwood. May cause neurological effects such as arm or leg numbness, delirium and paralysis.
  
  
• Yohimbe. May result in kidney failure, stomach problems, fatigue, seizures, paralysis and death.  

Certain supplements taken for long periods of time may also cause problems. For example, echinacea taken every day for more than two months may damage the liver. This risk is increased in patients taking other medications that may cause liver damage.

There are many types of supplements that may be unsafe in certain circumstances. For example, some types of hormone supplements (e.g., androstenedione) may be harmful when used by adolescents whose bodies are still developing. Parents should consult their child’s physician or a registered dietitian before providing any type of supplement to children or teenagers. 

Symptoms of adverse reactions that may occur with supplements includes:

• Abdominal pain
• Nausea
• Headache
• Hair loss
• Skin rash
• Fatigue
• Dizziness
• Diarrhea (may be black or bloody)
• Shock
• Liver or kidney damage
• Coma
• Birth defects