Why Do Multivitamins Have More Than the RDA?
Many people pick up a multivitamin, glance at the label, and feel alarmed when they see nutrient amounts exceeding 100%—sometimes 200% or more—of the Recommended Dietary Allowance (RDA). If the RDA is the recommended daily intake, why would anyone need more? The answer lies in how RDAs were originally created and how our understanding of nutrition has evolved.
RDAs: DESIGNED FOR DEFICIENCY PREVENTION, NOT OPTIMAL HEALTH
The Recommended Dietary Allowances (RDAs) and Adequate Intakes (AIs) were established in the 1940s and 1950s to prevent acute nutrient deficiencies. These guidelines ensured people were getting enough nutrients to avoid diseases like:
Scurvy (vitamin C deficiency)
Beri beri (thiamine/vitamin B1 deficiency)
Pellagra (niacin/vitamin B3 deficiency)
Rickets (vitamin D deficiency)
While these values were—and still are—useful for preventing outright disease, they don’t necessarily reflect the nutrient levels needed for optimal function, longevity, and disease prevention. RDAs are based on the minimum needed for survival, not the amounts that might promote energy, mental clarity, immune resilience, or long-term wellness.
WHO SETS THE RDAs?
The Food and Nutrition Board (FNB) of the National Academies of Sciences, Engineering, and Medicine (NASEM) (formerly the Institute of Medicine, IOM) is responsible for setting the Dietary Reference Intakes (DRIs) in the U.S. and Canada. The DRIs include:
Recommended Dietary Allowance (RDA) – the estimated daily intake that meets the needs of 97-98% of the population.
Adequate Intake (AI) – used when there isn’t enough data to set an RDA.
Tolerable Upper Intake Level (UL) – the highest intake level unlikely to cause harm.
WHY DO MULTIVITAMINS CONTAIN MORE THAN THE RDA?
RDAs Are Minimums, Not Ideal Targets
Think of the RDA as the nutritional equivalent of a “bare minimum” salary—it might keep you afloat, but it’s not designed for thriving. Multivitamins often contain higher amounts because research suggests that optimal health may require more than the lowest necessary intake.
Nutrient Absorption Varies
The body doesn’t absorb 100% of every nutrient we consume. Factors like gut health, age, stress, medications, and genetics can impact how well we absorb vitamins and minerals.
Example: Vitamin B12 has an RDA of 2.4 mcg, but many multivitamins contain 100 mcg or more because absorption is inefficient, especially in older adults (who tend to have lower stomach acid) or those with gut issues.
Example: Magnesium has an RDA of 310-420 mg, yet many experts suggest 500-600 mg due to widespread depletion in soil and diets.
Modern Lifestyles Increase Nutrient Needs
The RDAs were set decades ago, and life today is very different:
Chronic stress increases the demand for B vitamins, magnesium, and vitamin C.
Soil depletion has lowered the nutrient content of food.
Medications (like birth control or metformin) deplete key vitamins like folate and B12.
Toxins and pollution increase the need for antioxidants like vitamins C and E.
Some Nutrients Have High Safety Margins
Many vitamins, especially water-soluble ones (B vitamins and vitamin C), have a high margin of safety. The body excretes excess amounts through urine rather than storing them, so supplementing above the RDA is generally safe.
Example: The RDA for vitamin C is 75-90 mg, but doses of 500-1000 mg have been linked to improved immune function, collagen production, and antioxidant benefits.
RECENT UPDATES TO RDAS: ARE THEY KEEPING UP?
Some RDAs and AIs have been revised over the years based on new research, but many remain outdated compared to the latest science. The NASEM is responsible for updating these guidelines. Here are some notable changes:
Vitamin D (2011 update): Increased from 200 IU to 600-800 IU, but many experts argue that 1000-4000 IU is more beneficial for immune function, bone health, and chronic disease prevention.
Potassium (2019 update): The AI was lowered from 4700 mg to 3400 mg (men) and 2600 mg (women), despite potassium’s role in blood pressure regulation.
Sodium (2019 update): The AI was set at 1500 mg/day, with a recommended limit of 2300 mg/day to reduce hypertension risk.
Choline (1998 AI establishment): Choline was not originally considered essential, but an AI was set at 425-550 mg/day due to its role in brain function and methylation. Many people don’t meet this from diet alone, especially vegetarians and vegans. Eggs are rich in choline.
WHAT RDAs MIGHT STILL BE TOO LOW?
While updates occur periodically, several RDAs are still considered too low for optimal health. These include:
Vitamin D: RDA is 600-800 IU, but many need 1000-4000 IU for immune and bone health.
Magnesium: RDA is 310-420 mg, yet many benefit from 500-600 mg due to high stress and poor soil quality.
Vitamin C: RDA is 75-90 mg, but doses of 250-1000 mg offer added immune and skin benefits.
Vitamin B12: RDA is 2.4 mcg, but many experts recommend 10-100 mcg for better absorption.
Omega-3s: There is no official RDA for omega-3 fatty acids, but the American Heart Association recommends 250-500 mg EPA/DHA daily for cardiovascular health, while higher amounts (~1000-2000mg) may be beneficial for reducing inflammation and supporting brain health.
WHEN MIGHT HIGHER DOSES BE A CONCERN?
While many nutrients have a high safety threshold, some should be taken in appropriate amounts:
Fat-soluble vitamins (A, D, E, K): Unlike water-soluble vitamins, these are stored in the body, so excessive amounts could accumulate over time.
Iron & Copper: Too much iron can cause oxidative stress, and excessive copper can impact neurological health. These should be taken based on individual needs.
Folic Acid vs. Methylfolate: Some people have MTHFR mutations that reduce their ability to convert synthetic folic acid into its active form, methylfolate.
REASSURANCE
When you see something like 200% above the RDA, that amount can seem “high” but, remember:
RDAs are minimums, not optimal health targets.
Modern factors like stress, medications, and food quality increase nutrient needs.
Higher amounts in multivitamins account for absorption rates and individual variations.
The body naturally regulates excess amounts of most vitamins, especially water-soluble ones.
If you're unsure about what’s right for you, consider testing your nutrient levels and tailoring supplementation to your individual needs. Multivitamins are not about “megadosing”—they’re about filling the gaps where modern diets and lifestyles fall short.
Still have concerns? Let’s talk about it in the comments below! Or book a consultation to assess your individual needs.
