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Side Effects of GNC Mega Men Dietary Supplement

author image Brian Willett
Brian Willett began writing in 2005. He has been published in the "Buffalo News," the "Daytona Times" and "Natural Muscle Magazine." Willett also writes for and He is an American Council on Exercise-certified personal trainer and earned a Bachelor of Arts in journalism from the University of North Carolina.
Side Effects of GNC Mega Men Dietary Supplement
A small heart-shaped box filled with supplements. Photo Credit: gitusik/iStock/Getty Images

GNC Mega Men is a multivitamin supplement produced by supplement retailer GNC, also known as General Nutrition Centers. Mega Men contains vitamins, minerals and antioxidants and is designed to support the nutritional needs of active men. Although supplementation of GNC Mega Men can be beneficial, using this supplement could cause some side effects. Consult a medical professional prior to using Mega Men or any other supplement.

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GNC Mega Men contains carnitine, an amino acid that aids in metabolizing food. However, too much carnitine can cause diarrhea. Unfortunately, GNC does not disclose the exact amount of carnitine in Mega Men, as it is part of a proprietary ingredient blend.

Itching and Rashes

Itching and rashes are common signs of allergic reactions, which are a potential side effect of any supplement. However, specific ingredients in GNC Mega Men may promote these effects as well. The most likely culprit is vitamin B12; GNC Mega Men contains more than 800 percent of the daily suggested intake of this vitamin, and high levels can promote itching and rashes.

Nausea/Upset Stomach

Using GNC Mega Men may cause you to experience nausea. This nausea can be linked to the high level of panthothenic acid, or vitamin B5; each serving of GNC Mega Men contains five times the daily recommended intake, and according to the Linus Pauling Institute, most people already get enough of this vitamin because it's present in so many foods. You may also experience gastrointestinal distress due to the vitamin B1 content, as GNC Mega Men provides more than 33 times the suggested intake.

Nerve Damage

Another vitamin that GNC Mega Man provides a large dose of is vitamin B6. Each two-capsule serving of Mega Men contains 2,500 percent of the daily suggested intake of this vitamin, which aids in the production of hemoglobin. However, high intakes of vitamin B6 have been known to cause nerve damage.

Headache and Dizziness

GNC Mega Men contains high levels of vitamin A, a nutrient that promotes healthy vision. However, too much vitamin A can lead to dizziness and headaches.

Reduced Insulin Sensitivity

GNC Mega Men is intended to be taken as part of a healthy diet and in conjunction with exercise. However, the high levels of vitamin C -- five times the daily suggested intake -- and vitamin E -- an entire daily dose -- in GNC Mega Men may counteract some of the effects of exercise and healthy eating. According to research published in the May 2011 issue of "Proceedings of the National Academy of Sciences of the United States of America," vitamins C and E inhibit the improvements in insulin sensitivity normally promoted by exercise. Increased insulin sensitivity can help you gain muscle and shed fat; impaired insulin sensitivity is related to diabetes and obesity.

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