Vitamin D helps your body maintain proper levels of calcium and phosphorus, two nutrients important to the strength of your bones. The B vitamins aid digestion and help your liver and nervous system function properly. Most people get enough vitamins D and B from their diets. Supplements can help correct deficiencies but, if you take more than you need, side effects, including diarrhea, may occur.
Vitamin D
Vitamin D will more likely cause constipation than diarrhea if you take excessive amounts. Other side effects include nausea, decreased appetite, weakness and weight loss. More seriously, excess vitamin D can cause mental confusion, irregular heartbeat and kidney stones. You can obtain vitamin D from dairy products, including milk and cheese. Some non-dairy products are fortified with vitamin D. You can also absorb vitamin D through sun exposure, although this proves more difficult if you are dark-skinned.
Vitamin B-3
Vitamin B-3, also known as niacin, can cause diarrhea and vomiting if taken in high amounts of more than 100 mg a day. Vitamin B-3 helps your body convert carbohydrates to sugar and to metabolize proteins and fats. It also helps strengthen your hair, nails and eyes. Your diet supplies about 14 mg to 16 mg a day from foods such as nuts, fish, yeast, chicken, eggs and milk. Some supplements contain as much as 500 mg niacin. Serious side effects of taking excess niacin include stomach ulcers, gout, vision loss and liver damage.
Vitamin B-5
Vitamin B-5 may cause diarrhea if you take more than the recommended daily dose of 5 mg a day. Vitamin B-5 -- pantothenic acid -- occurs naturally in a variety of vegetables, legumes, cereals, meats and dairy products. If you have a B-5 deficiency, you may take up to 10 mg a day. People take B-5 for a variety of reasons, including treating attention-deficit hyperactivity disorder, skin problems and hair loss, but little evidence supports most uses of B-5. Taking B-5 could increase symptoms of hemophilia, a blood-clotting disorder.
Considerations
If you take vitamin B complex, a multivitamin that may contain six or more B vitamins, check labels for ingredients and dose. Some supplements contain very high amounts -- more than 6,000 percent of the recommended daily allowance -- for B vitamins. While only a few B vitamins prove likely to cause diarrhea, all can turn toxic if taken in high doses. Minor side effects include a change in urine color and output, sleepiness, headaches and stomach upset. More serious side effects include nerve and brain damage and, if you have kidney disease, taking B complex could deteriorate your condition.
References
- University of Maryland Medical Center; Vitamin B3 (Niacin); June 18, 2009
- Medline Plus: Thiamine (Vitamin B1); May 9, 2011
- Medline Plus; Riboflavin (Vitamin B2);Nov. 19, 2010
- Medline Plus: Pantothenic Acid (Vitamin B5); Nov. 19, 2010
- Medline Plus: Pyridoxine (Vitamin B6); Dec. 13, 2010
- Centers for Disease Control and Prevention; Learn More about Vitamin B12 Deficiency; Aug. 3, 2009
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