Vitamin C, also called ascorbic acid, is a powerful vitamin that has a wide range of effects on your body. Rose hips are the fruit of the rose plant and contain large amounts of natural ascorbic acid. Commercial manufacturers of vitamin C extract ascorbic acid from the rose hips and solidify it into a tablet or capsule to be sold as vitamin C with rose hips. Vitamin C is water soluble, making side effects rare. However, large doses of vitamin C have been known to cause such side effects as indigestion, hemochromatosis, hormone suppression and oxygen processing problems during exercise.
Large doses of vitamin C might cause indigestion, especially if you consume it on an empty stomach. Excess vitamin C intake might also cause diarrhea and increase the risk of other symptoms of indigestion, including nausea, vomiting, headaches, and fatigue. This might be due to the natural acidity of vitamin C. Ingesting calcium ascorbate with large doses of vitamin C might help neutralize the acidity of vitamin C in your stomach and reduce the risk for developing symptoms of indigestion.
Vitamin C has been known to increase the absorption of iron into your bloodstream and is often recommended for individuals who take iron supplements to treat a deficiency. However, ingesting too much vitamin C and iron together can increase the risk for developing iron poisoning, called hemochromatosis. An iron overload can lead to liver and pancreas damage, heart palpitations, arthritis and testicular damage. Very large doses of vitamin C might also cause hemolytic anemia, or a breakdown in red blood cells that is sometimes attributed to iron poisoning.
High doses of vitamin C might affect the production of sex hormones such as progesterone, especially in women during pregnancy. Progesterone is an important hormone that supports gestation during pregnancy. Excess vitamin C in the bloodstream might inhibit the natural release of progesterone. Blocking the release of progesterone in the early stages of pregnancy increases the risk of birth defects and miscarriages.
During exercise, your body's various tissues require more oxygen to function than when your body is at rest. The measurement of maximal oxygen consumption by your body during exercise is called your VO2Max. High doses of vitamin C might lower the expected effect of training on your VO2Max, indicating that vitamin C, when overdosed, can have a negative effect on athletic performance. Although the exact mechanisms of this effect remain somewhat unclear, the acidity of vitamin C might interfere with your body's ability to deliver oxygen to your muscle tissues through your bloodstream.