Some studies suggest that vitamins B6 and B12 may impact your sleep. Taking B6 before going to bed may cause vivid dreaming (which will wake you up during the night), and vitamin B12 may keep you awake because it affects your melatonin levels, a hormone in your body that helps to regulate your sleep/wake cycle.
B Vitamins: The Energy Vitamins
The B vitamins are considered "energy vitamins" because they play an important role in energy metabolism, which means it helps the body be more efficient in how it turns the fats, carbohydrates and proteins from the foods we eat into usable energy to get us through our day.
There are 11 components that make up what we usually refer to as B-complex vitamins, and your body has different uses for each. They include vitamins B1 (thiamine), B2, (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B9 (folic acid), B12 (cyanocobalamin) as well as the nutrient supplements biotin (known also as vitamin H), para-amino benzoic acid (PABA, or sometimes called vitamin Bx or vitamin B10), choline and inositol.
Let's look specifically at vitamin B12. It's estimated that as many as 15 to 40 percent of people in the U.S. have some level of B12 deficiency [source: Geagan]. B12 is important because it helps your body turn carbs into the glucose your body uses to keep you alert and active instead of fatigued and sluggish (B3 also has these energy boosting benefits). B12 may also help lift your brain fog and help your focus and memory.
Vitamin B6 is also being studied as another vitamin in the B family that may boost your alertness, and preliminary studies show it may help prevent the decline in our cognitive function as we age.
Your body also uses B vitamins in its production of new healthy cells and red blood cells, and they are critical to how well your immune system, cardiovascular system and nervous system function.
If boosting your Bs for energy doesn't seem to get you back on your toes, consider iron and magnesium supplements -- an iron deficiency (and iron-deficient anemia) can leave you feeling tired, with trouble concentrating, and magnesium, like those B vitamins, is needed in the process of converting food into energy.