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Too much of a good thing?

The risk of eating nutrient-enhanced foods

Last updated: November 2013

Superjuices, energy shots, vitamin-infused nutrition bars—grocery stores teem with foods that have been pumped up with nutrients during processing. A 12-ounce bottle of Odwalla Superfood Blueberry B Premium Fruit Smoothie Blend, for example, delivers up to 530 percent of the recommended daily value of the B vitamins thiamin, riboflavin, B6, and B12.

That’s good, right? Not necessarily. Eat enough fortified foods in a day—especially along with a multivitamin or a single-ingredient supplement like calcium—and you could end up not only with more of an ingredient than you need but also more than is good for you.

Illustration: Leigh Wells

We calculated how much caffeine, calcium, folate, and vitamin C a person might consume in a day. All of those can have undesirable effects in very high doses. Our hypothetical consumer breakfasted on coffee, cereal, orange juice, a multivitamin, and a couple of calcium chews; snacked on a nutrition bar; lunched on a peanut-butter-and-jelly sandwich and lemonade; snacked on a protein shake; had an energy shot as an afternoon pick-me-up; dined on mac and cheese; and took two packets of a cold remedy and a couple of headache gelcaps at various times during the day.

The day’s tally

Here’s what our nutrient-rich consumer took in: 537 milligrams of caffeine (more than 100 milligrams too much); 376 percent of the recommended daily value of calcium; 3,952 percent of the recommend­ed daily value of vitamin C; and 540 percent of the recommended daily value of folate.

Ingredients other than those we’ve highlighted can cause problems, too. Some studies have linked high blood levels of iron to an elevated risk of heart disease and type 2 diabetes, and iron supplements can interfere with the body’s absorption of zinc. Too much vitamin A can cause birth defects and liver damage.

Some of the products we used in our cal­culations have other extras: The 5-hour Energy Extra Strength shot our consumer drank (242 milligrams of caffeine) also has 200 percent of the daily value of niacin, 2,000 percent of vitamin B6, and 8,333 percent of vitamin B12. (Read our recent report "The Buzz on Energy-Drink Caffeine." )

Bottom line. A balanced diet rich in fruits and vegetables, low-fat dairy products, lean protein, whole grains, and legumes should provide all you need of major vitamins and minerals, plus fiber and a rainbow of healthful phytochemicals. If you eat a restricted diet or need more of certain nutrients, a multivitamin or individual supplement can plug the gaps. To avoid becoming overfortified, read labels on processed foods. Although manufacturers don’t have to list caffeine levels, they must list amounts of added vitamins and minerals.

The risks you run


Most adults can safely consume up to 400 milligrams a day; pregnant women up to 200 milligrams.

Risks of too much: jitters, insomnia, rapid heart rate, abnormal heart rhythm, increased blood pressure.


Recommended daily value: 1,000 to 1,200 milligrams. Upper limit: 2,000 to 2,500 milligrams.

Risks of too much over time: constipation, kidney stones, impaired absorption of iron and zinc.


Recommended daily value: 400 micrograms. Upper limit: 1,000 micrograms.

Risks of too much over time: masking of B12 deficiency, which causes nerve damage. Deficiency is most common in people 50 or older or vegetarians.

Vitamin C

Recommended daily value: 60 mg. Upper limit: 2,000 mg.

Risks of too much: diarrhea, nausea, vomiting, heartburn, abdominal cramps, bloating.

Visit our Food & Drink Guide to find out more about healthy eating and food safety.

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