Vitamin B supplements may be a waste of money if you're eating a healthy and varied diet.

Pick up a bottle of vitamin B supplements and you’re likely to see some sort of claim that the pills inside will boost your energy. Peruse the energy-drink section of the grocery store and you’ll find that many of them have added B vitamins and make the same claim.

Trouble is, B vitamins don’t give you energy. No vitamin gives you energy.

Calories give you energy. Specifically, calories in the form of glucose, which is found in carbohydrate-containing foods (grains, beans, vegetables, fruits, dairy).

Let me explain. Your body’s cells break down glucose into an important molecule commonly known as ATP, which is the form of energy that cells use to power their life-sustaining operations. If your cells couldn’t generate ATP, you would die.

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The B vitamins play essential roles in the complex biochemical machinery that breaks glucose into ATP, releasing energy from the food we eat. In that way, B vitamins make it possible for your body to use energy — but they don’t contain energy.

If you are deficient in B vitamins (most people are not), this can affect your energy levels. But so can other things, including lack of sleep. If you have adequate B-vitamin levels but pop a supplement anyway, you won’t gain extra energy. Your body will simply excrete the excess in your urine. Don’t waste your money.

Another problem with taking nutrients in supplement form is that they often work closely together, and levels of one vitamin affect how another vitamin works. For example, if Vitamin X relies on Vitamin Y, but you have a lot of X and not enough Y, it’s as if you have too little of both.

This is especially true with the B vitamins, which are highly dependent on each other. Yet, it’s common for B-complex supplements to contain 50 milligrams of each individual vitamin. That means it has 3,333 percent of the thiamin you need each day, but only 17 percent of the biotin. The potential imbalance could be even greater if you take supplements of a single B vitamin.

The eight B vitamins — thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), B12 and folic acid (folate) — are often found in the same foods.

The richest sources are fish, poultry, meat, eggs, and dairy products. Leafy green vegetables, lentils, beans, peas and whole grains also have B vitamins. Many cereals and some breads have B vitamins added. Nutritional yeast and brewer’s yeast (but not baker’s yeast) are other B sources.

If you eat a varied diet, you’re probably getting enough B vitamins. B12 is found only in animal products, so vegans often need B12 supplements, unless they are eating foods fortified with B12. Low levels of B12 or B6 can cause anemia, and many people have trouble absorbing B12 as they get older.

Next time: How to handle food pushers.

Carrie Dennett:

Dennett is a graduate student in the nutritional-sciences program at the UW; her blog is