Niacin and magnesium affect some of the same systems in your body but in different ways. As a result, taking them together may benefit your overall health, from producing plenty of energy to protecting your heart. In supplemental form, both nutrients can cause side effects, so consult your doctor if you have any health concerns.

Energy and Metabolism

Your body uses niacin to produce nicotinamide adenine dinucleotide, or NAD, and nicotinamide adenine dinucleotide phosphate, or NADP. You must have niacin to produce energy. NAD and NADP enable more than 400 enzymes to do their jobs, with NAD often breaking down nutrients, while NADP usually helps build vital compounds, such as cholesterol.

Like niacin, magnesium supports hundreds of enzymes. In that role, magnesium is essential to produce energy and synthesize DNA, proteins, carbohydrates and lipids. As an electrolyte, magnesium can carry an electrical charge, which makes it important for nerve impulses and muscle function. Magnesium also helps build bones.

Cardiovascular Benefits

Magnesium keeps your heart beating at a regular pace. A report in the Annals of Nutrition and Metabolism in 2012 stated that magnesium relaxes the muscles in blood vessel walls, which lowers blood pressure 3.

Niacin and magnesium reduce the risk of developing hardening of the arteries. They also increase blood levels of high-density lipoproteins, or HDLs, which are better known as good cholesterol. HDLs actually help lower cholesterol by carrying it to the liver for elimination from your body. Niacin also reduces bad cholesterol, or low-density lipoproteins. Prescription-strength doses of niacin are needed to affect cholesterol, however.

Prevent Diabetes

A deficiency in magnesium is commonly found in people with diabetes. A review in the Clinical Journal of the American Society of Nephrology in 2007 reported that about 14 percent to nearly 50 percent of people with type-2 diabetes are low in magnesium 56. On the flip side, getting the right amount of magnesium results in a lower risk of developing type-2 diabetes, reported the Journal of Internal Medicine in August 2007 5.

Niacin may protect the health of the pancreas in people with type-1 diabetes, which is often diagnosed at a young age and must be treated with insulin. Because the pancreas produces insulin, niacin may help prevent diabetes, but studies so far have produced conflicting results, according to the Linus Pauling Institute 12.

Daily Intake of Magnesium

The recommended dietary allowance for magnesium is 320 milligrams daily for women and 420 milligrams for men. If your magnesium comes from foods, such as:

  • leafy greens
  • whole grains
  • nuts
  • low-fat milk
  • lean meat
  • you don’t need to worry about side effects

Supplements can cause diarrhea if you take more than the upper safe intake of 350 milligrams. In larger doses, blood pressure drops, muscle weakness develops and you may have a hard time breathing.

Niacin Recommendations and Warnings

Women should consume 14 milligrams of niacin daily, while men need 16 milligrams. Just like magnesium, side effects don’t occur when niacin comes from your diet.

Taking supplements in doses that exceed the safe upper intake of 35 milligrams can cause flushing, itching, nausea and vomiting. In larger doses, niacin may damage your liver, especially if you take timed-release niacin, according to studies cited by the Linus Pauling Institute 12.

Talk to your doctor before taking niacin supplements if you have liver disease, diabetes, an irregular heartbeat, inflammatory bowel disease, migraine headaches, peptic ulcer disease or gout.