Dietitians explain why it isn’t always accurate.
Unless you’re a professional in the nutrition space, there’s a good chance you don’t know how much of each nutrient you should be getting each day off the top of your head. That’s what Google is for, right?
Anytime you look up a nutrient need, the answer inevitably lies in the recommended daily allowance (RDA). RDA is different from Percent Daily Value (%DV), which is what appears on food and supplement labels. “Percent Daily Value is set by the Food and Drug Administration (FDA) and represents how much of a nutrient is in a [food, drink, or supplement] based on a 2,000 calorie diet,” explains registered dietitian Theresa Shank, MS, RD, LDN. RDA on the other hand takes into account one’s sex and age (and if you’re pregnant), says Shank. That’s why when you Google your nutrient needs, a chart will pop up, giving different amounts based on these factors.
RDA has long been the standard we rely on to know our nutrient goals and while it’s helpful, it isn’t perfect. If you really want to maximize your nutrition, you shouldn’t rely on RDA alone.
Where Did RDA Come From?
Toby Amidor, MS, RD, CDN, FAND award-winning nutrition expert and author of The Family Immunity Cookbook, explains that the first edition of RDA was published in 1943 during World War II as a way to provide standards for good nutrition. Registered dietitian Whitney English Tabaie, MS, RDN, says that these guidelines were established by the U.S. National Research Council. “The initial recommendations were for protein, calories, and eight vitamins and minerals,” she says. “The purpose of the first RDA was to help with food relief efforts and meet nutrition adequacy during the war and economic depression era when malnutrition was common.”
Then, in 1973, the federal government established the RDA to be used as a reference on food labels. (Labeling was voluntary at the time, not becoming mandatory until 1994.) “The RDA of each nutrient was the amount thought to be necessary to maintain good health,” Amidor says. In 1994, she says that the FDA introduced Percent Daily Values (%DVs), which is what appears on food labels today.
Tabaie says that the formula used to determine RDAs is based on the average daily dietary nutrient intake level that meets the nutrient requirements of most (97.5%) healthy individuals in a particular life stage and gender group. “However, these values did not take chronic disease or obesity into account,” she adds. And this is where the problem lies.
When RDA Comes In Handy—And When It Doesn’t
All three dietitians say that RDA is helpful when it comes to figuring out the average calorie and nutrient intake for the vast majority of people. If you are generally in good health, eat roughly 2,000 calories a day, don’t have any underlying health conditions, and don’t take any medications, RDA can serve as a good guideline for you.
If you do have an underlying health condition, are either underweight or overweight for what is considered “normal” for your sex and age, eat considerably more or less than 2,000 calories a day, or take any medications, all three dietitians say this is where RDA falls short; it doesn’t take into account variances like these. “They’re not individualized; they’re meant as a [general] guide,” Amidor says.
Shank says that people who have health conditions such as Crohn's disease, cancer, an autoimmune condition, or who are a transplant recipient—to give just a few examples—fall outside the scope of the RDA recommendations. One reason for this is because certain medications interact with nutrient absorption. “I had a client today who takes a hypertensive medication, which causes the kidneys to excrete sodium, which then causes the body to hold onto potassium, for example,” she says.
How To Know Exactly What Your Body Needs
How can you know for sure what your individual nutrient needs are? This is when you need to talk to a professional. Shank says that consulting a registered dietitian or licensed pharmacist can be helpful to get nutrition guidance tailored to your specific needs. Amidor adds to this saying, “If you really want an in-depth analysis, see a registered dietitian nutritionist who can calculate your daily intake and their macro and micronutrients.”
Amidor warns against getting too obsessed. “There really is no need to know exactly [every nutrient value] that you are eating daily. That can lead to disordered eating if you calculate everything you put in your mouth all the time,” she says. Simply put, it takes the enjoyment out of eating. “But if you want a snapshot on how you're doing, a RDN can certainly help by providing feedback on your food and beverage intake and help make positive steps towards meeting your health goals,” she says.
The bottom line is that RDA is a helpful general guideline, but if you have an underlying health condition, take medication, or consume considerably less or more than 2,000 calories a day, it’s worth it to work with a professional who can give you tailored advice. That’s the only way to know what’s best for you as an individual and not just someone of a specific sex and age.