Both vitamin K and niacin are important for good health; the vast majority of available multivitamins provide both nutrients. However, certain medications may require you to minimize your vitamin K consumption, while experiencing side effects from consuming the form of niacin found in many multivitamins may mean you need to switch to a different source of niacin. You should follow your doctor’s advice about what multivitamins are right for you; he may recommend on like Clotamin, which contains no vitamin K, or Jamieson Basic Vita-Vim, which contains only niacinamide.
Vitamin K is critical for allowing your body to form blood clots — otherwise, a small scratch could continue bleeding and become dangerous. However, vitamin K also contributes to building strong, healthy bones; according to the University of Maryland Medical Center, it can help prevent osteoporosis. You can find vitamin K in beef liver, as well as in many dark green, leafy vegetables.
Niacin is also known as vitamin B-3. As part of the B complex, niacin helps convert the food you eat into useable energy; it also contributes to a healthy circulatory system and to the creation of many of your body’s different hormones. You can find niacin in both red and white meat, fish, seeds and beans, as well as in multivitamins, according to the Linus Pauling Institute from Oregon State University.
Supplemental niacin may occasionally cause such side effects as itchy or flushed skin, upset stomach and vomiting in some people. You should consult your physician if you experience these symptoms; he may recommend that you limit your intake to nicotinamide, also known as niacinamide, which is a derivative of niacin that generally is less likely to cause such side effects. However, he may also simply have you consume all your niacin requirements from food, since naturally occurring niacin has not been found to cause harmful effects.
REFERENCES
http://www.umm.edu/altmed/articles/vitamin-k-000343.htm
http://lpi.oregonstate.edu/infocenter/vitamins/niacin/
http://www.clotamin.com/sitefiles/multivitamin-without-k
http://www.jamiesonvitamins.com/node/135
http://www.umm.edu/altmed/articles/vitamin-b3-000335.htm
http://www.nlm.nih.gov/medlineplus/ency/article/002407.htm