If you’ve read a nutrition label, you may have noticed the label states how much of a vitamin or mineral is in each serving of that food. Beside it is listed a %DV or % daily value. This tells what percentage of the recommended daily value that serving provides. For example, suppose a product states that a serving supplies 20 milligrams of calcium. You look beside that number and see 20% under %DV. Now, you’re aware that one serving offers 20% of the daily value. But what does daily value really mean and is consuming 100% of the daily value for a vitamin or mineral enough for good health?
First, %DV is a value set forth by the FDA. It’s based on recommended daily intake (RDI), a value that estimates how much a person who eats a 2,000-calorie diet needs each day. The RDI is a generalization and doesn’t take into account a person’s gender or age. It applies to all adults age 4 and over. The %DV shows how much of a particular vitamin or mineral one serving of a product supplies based on its RDI.
What Does RDA Mean?
To confuse matters more, the Institute of Medicine uses a different term called the recommended dietary allowance. (RDA). It, too, is an estimate of how much an individual should get of a particular vitamin or mineral each day. But you won’t see this value on packaging as packaging falls under the jurisdiction of the FDA and the FDA uses %DV derived from the RDI.
Where does the Institute of Medicine get RDA values? RDA determination goes a step beyond the RDI. These values take into account age, gender, and whether a woman is pregnant in establishing values. It also introduces two other terms: adequate daily intake (AI) and tolerable upper limit (UL). Adequate intake is the minimum amount you need to avoid becoming deficient in a vitamin or mineral. The tolerable upper limit is the greatest amount your body can tolerate without developing signs of toxicity.
Meeting Your Body’s Vitamin and Mineral Requirements
What’s the practical application? %DV is a good reference to have when you’re comparing packaged products at the grocery store. At a glance, you can tell whether a serving of a particular product is a good source of each vitamin or mineral. For example, if a serving only provides 3% of the %DV for magnesium, you know you’ll have to eat a lot of that product to meet your body’s magnesium requirements. Alternatively, you’ll have to eat other foods high in magnesium to make up for the shortfall.
The downside is %DV is derived from the RDI, a value based on the nutritional needs of the average person. It assumes that an 80-year-old female has the same nutritional needs as a 5-year-old boy and everyone in between has similar requirements. That’s not the case. It doesn’t even take into account additional nutritional needs during pregnancy or breastfeeding. It only gives a general approximation of nutritional needs based on an average, healthy human being.
In some ways, the RDA value, set by the Institute of Medicine, is a better indicator how much of a particular vitamin or mineral you need in a day because it takes into account age and gender. But, when you look at food packaging, you’re stuck with the %DV based on the RDI. But, it can still give you a general idea of whether a food is nutrient dense.
Based on the way RDA and RDI are determined, consuming 100% of the DV of a vitamin or mineral doesn’t necessarily mean you’re getting optimal nutrition. If you exercise intensely or have a highly active lifestyle, you may need more than 100% of the daily value because these values don’t take into account your active lifestyle. The RDI and RDA also don’t consider medical conditions that can impact nutritional status and increase the requirement for certain vitamins and minerals. Even some medications can deplete nutrients. For example, some diuretics and blood pressure medications use up potassium and magnesium.
Age can also impact how much of some vitamins and minerals you need. There’s evidence that older people may need more zinc in their diet for healthy immune function. Gender matters too. For example, pre-menopausal women need more iron than men. Women have slightly higher calcium needs relative to men too. Smokers need as much as twice the quantity of vitamin C that a non-smoker does due to the higher levels of antioxidant stress their body is exposed to.
Even the RDA, a measure that takes into account age and gender, is only a rough guide. The Institute of medicine came up with the RDA in the 1930s during the Great Depression. These values were based on the minimum quantity of vitamins and minerals a sedentary person would need to maintain health. The values have since been updated several times but are still based on minimums rather than optimal quantities.
The Values Establish a Baseline Level of Nutrition
It’s best to use the %DV and RDA only as a rough guideline and realize they were established to avoid deficiency. They aren’t even necessarily accurate for doing that since they don’t consider factors like health issues and activity level. Your nutritional needs may be different because of how physically active you are or because you have health issues or take medications that deplete vitamins or minerals.
How Should You Use These Values?
When you’re eyeballing a product at the grocery store, the %DV gives you a rough idea of how nutritious a product is. This information offers a quick way to size up a product. But, it’s not the full story. Go a step further and look at the ingredient list. Some highly processed products are fortified with synthetic vitamins and minerals but are still high in sugar, cheap oils, and fillers. Take these factors into account when you decide whether to purchase a product.
Even better? Think out of the package. If you stick to a whole food, nutrient-dense diet with lots of fruits, non-starchy vegetables, lean protein, and healthy fats, you’ll go a long way toward meeting your body’s nutritional needs, assuming you’re consuming enough calories. If you have a medical condition or take medications, check with your physician to find out whether you should alter your diet based on your health or medications. If in doubt, see a dietitian.
· Food and Drug Administration. “Changes to the Nutrition Facts Label”
· National Academies Press. “History of Nutrition Labeling”