07/21/2025
What would a highly respected functional medicine doctor (AKA Mark Hyman) recommend for supplementation? What is RDA? AI?
What exactly do the Recommended Dietary Allowance (RDA) and Adequate Intake (AI) mean?
These guidelines help determine how much of each nutrient you should consume to avoid deficiency-related diseases but they don’t provide an optimal intake for peak health.
Recommended Dietary Allowance (RDA): The RDA is the average daily level of nutrient intake that’s sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals in a particular life stage and gender group. It’s based on scientific research and is meant to cover the needs of the majority of the population.
Adequate Intake (AI): The AI is established when there isn’t enough evidence to develop an RDA. It’s the recommended average daily intake level based on observed or experimentally determined estimates of nutrient intake by a group of healthy people. AI is used as a guideline when an RDA cannot be determined, and it provides a target for nutrient intake that is assumed to ensure nutritional adequacy.
Essential Vitamins
Vitamins are organic compounds that are crucial for maintaining your health, and there are 13 vitamins that are considered essential for your body’s normal functioning. These essential vitamins are divided into two categories based on how they are absorbed and stored in the body:
Fat-soluble vitamins: These vitamins (A, D, E, and K) are stored in the body's fatty tissues and liver. They can remain in your body for longer periods, and your body can draw on these stores when needed.
Water-soluble vitamins: These include the eight B-complex vitamins (B1, B2, B3, B5, B6, B7, B9, B12) and vitamin C. Water-soluble vitamins are not stored in large amounts and need to be replenished regularly through your diet, as excess amounts are excreted through urine.
Each of these essential vitamins plays a unique role in supporting your body’s growth, development, and overall health. While some vitamins, like vitamin D, can be synthesized by your body under certain conditions, others must be obtained entirely through your diet or supplements.
Type
Function
Source
RDA/AI
MRI (Mark’s Recommended Intake)
Vitamin A
Essential for vision, immune function, cognitive function, and skin health. Supports cell growth and differentiation, regulates gene expression, and influences thyroid hormone metabolism.
Carrots, sweet potatoes, spinach, and liver
RDA: 900 mcg/day (men), 700 mcg/day (women)
2000-3000 mcg/day
Vitamin C
Involved in collagen synthesis, antioxidant protection, and immune function. Enhances iron absorption, supports mitochondrial function, and reduces oxidative stress. May influence neurotransmitter synthesis and cognitive function.
Citrus fruits, berries, bell peppers, and broccoli
RDA: 90 mg/day (men), 75 mg/day (women)
1000 mg/day
Vitamin D
Facilitates calcium absorption, bone growth, and immune function. Modulates cell growth, neuromuscular function, and regulates cell cycle and differentiation. Linked to seasonal affective disorder (SAD) and depression.
Sunlight exposure, fatty fish, fortified dairy products, and egg yolks
RDA: 600 IU/day (ages 1-70), 800 IU/day (ages 70+)
5000 IU/day
Vitamin E
Acts as an antioxidant, protecting cell membranes from oxidative damage, and supports immune function. Maintains mitochondrial integrity and reduces oxidative stress.
Nuts, seeds, spinach, and vegetable oils
RDA: 15 mg/day
400 IU of mixed tocopherols/day
Vitamin K
Essential for blood clotting and bone metabolism, supports protein synthesis involved in blood coagulation, and indirectly supports cognitive function through blood health.
Leafy green vegetables, broccoli, and Brussels sprouts
AI: 120 mcg/day (men), 90 mcg/day (women)
90-300 mcg day of Vitamin K2 (menaquinone)
Vitamin B1* (Thiamin)
Involved in carbohydrate metabolism and nerve function. It’s crucial for converting nutrients into energy and supporting neural health.
Pork, whole grains, legumes, sunflower seeds, and fish
RDA:1.2 mg/day (men), 1.1 mg/day (women)
25 mg/day
Vitamin B2* (Riboflavin)
Supports energy production, cell function, and fat metabolism. It’s also essential for converting food into ATP.
Dairy products, eggs, lean meats, green leafy vegetables, almonds, and mushrooms
RDA: 1.3 mg/day (men), 1.1 mg/day (women)
25 mg/day
Vitamin B3* (Niacin)
Participates in DNA repair, stress responses, and metabolic processes. It helps convert nutrients into energy and aids in cholesterol management.
Poultry, fish, lean meats, peanuts, and whole grains
RDA: 16 mg/day (men), 14 mg/day (women)
25 mg/day
Vitamin B5* (Pantothenic Acid)
Vital for synthesizing coenzyme A, which is important for fatty acid metabolism and energy production.
Avocados, broccoli, mushrooms, whole grains, and sweet potatoes
AI: 5 mg/day
25 mg/day
Vitamin B6* (Pyridoxine)
Crucial for amino acid metabolism, neurotransmitter synthesis, and hemoglobin production. It supports cognitive development and immune function.
Poultry, fish, potatoes, bananas, and chickpeas
RDA: 1.3-1.7 mg/day
25 mg/day
Vitamin B7* (Biotin)
Involved in carbohydrate, fat, and protein metabolism. It supports healthy skin, hair, and nails.
Egg yolks, nuts and seeds, salmon, avocados, and whole grains
AI: 30 mcg/day
1-2 g/day
Vitamin B9* (Folate)
Folate is important for DNA synthesis and repair, cell division, and red blood cell formation. It supports fetal development and neural tube formation, is crucial for nucleotide synthesis and repair, and deficiency is linked to depression and cognitive decline.
Leafy green vegetables, legumes, asparagus, oranges and other citrus fruits, and beets
RDA: 400 mcg/day
400 to 800 mcg of methyl folate/day
Vitamin B12* (Cobalamin)
Important for nerve tissue health, brain function, and red blood cell production. It supports DNA synthesis and helps prevent anemia.
Fish, meat, poultry, dairy products, and eggs
RDA: 2.4 mcg/day
1000 mcg of methylcobalamin/day
* A B-Complex supplement can provide all the B vitamins.
Essential Minerals
There are 16 essential minerals, although the exact number is debated within the nutrition science community.
Typically, these essential minerals are divided into 7 macrominerals (calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur) and 9 trace minerals (iron, manganese, copper, iodine, zinc, cobalt, selenium, molybdenum, and chromium).
You’ll note that many of these minerals are described as “cofactors.” Cofactors are molecules that help your body’s processes work properly, like turning food into energy or building new cells. (Also: I’ve included three types of magnesium because, if you supplement, you’ll want to choose the form that best serves your needs.)
Type
Function
Source
RDA/AI
Mark’s Recommendation
Calcium
Integral for bone and teeth structure, muscle contraction, neurotransmitter release, and blood clotting. Acts as a secondary messenger in signal transduction pathways.
Dairy products, leafy green vegetables, fortified plant-based milks, almonds, and sardines
RDA: 1,000 mg/day (ages 19-50), 1,200 mg/day (ages 51+)
500 mg/day
Iron
Essential for oxygen transport and storage, ATP production, immune function, and cognitive development. Linked to fatigue and cognitive impairments when deficient.
Red meat, poultry, fish, lentils, beans, spinach, and fortified cereals
RDA: 8 mg/day (men), 18 mg/day (women)
Same
Magnesium
Cofactor for over 300 enzymatic reactions, supporting muscle and nerve function, blood glucose control, and protein synthesis. Stabilizes ATP and is necessary for DNA and RNA synthesis.
Pumpkin seeds, almonds, spinach, and dark chocolate
RDA: 400-420 mg/day (men), 310-320 mg/day (women)
Same, but if you supplement, choose the type below that best suits your needs.
Magnesium Citrate
If you have constipation and need some relief, this form of magnesium has a laxative effect and can help get your bowels moving.
Magnesium Glycinate
This form of magnesium is most widely used and comes without a laxative effect. It can help reduce the risk of cardiovascular disease and osteoporosis and also works well for those suffering from depression, anxiety, insomnia, and high blood pressure.
Magnesium L-threonate
Early animal research suggests this form can help overall brain health—including the potential to improve memory and learning—and is also a good choice for sleep issues.
Potassium
Regulates fluid balance, muscle contractions, and nerve signals. Maintains heart and kidney function, involved in mitochondrial function and ATP production.
Bananas, oranges, potatoes, spinach, and avocados
AI: 3,400 mg/day (men), 2,600 mg/day (women)
Same
Zinc
Supports immune function, wound healing, DNA synthesis, and cell division. Essential for taste and smell, acts as an antioxidant, and is linked to cognitive function and neurotransmitter regulation.
Meat, shellfish, legumes, seeds, nuts, and dairy
RDA: 11 mg/day (men), 8 mg/day (women)
15 to 30 mg/day
Selenium
Vital for antioxidant defense, thyroid hormone metabolism, and immune function. Plays a role in DNA synthesis, supports reproductive health, and may reduce the risk of certain cancers.
Brazil nuts, seafood, meats, eggs, whole grains, and dairy products
RDA: 55 mcg/day
200 mcg/day (with an upper limit of 400 mcg/day)
Iodine
Essential for the synthesis of thyroid hormones that regulate metabolism, growth, and development, critical for proper neurological function.
Iodized salt, seafood, dairy products, eggs, and seaweed
RDA: 150 mcg/day
Same
Copper
Involved in iron metabolism, formation of hemoglobin and red blood cells, synthesis of connective tissue, neurotransmitters, and melanin. Acts as a cofactor for several enzymes involved in energy production.
Shellfish, whole grains, nuts, seeds, legumes, and chocolate
RDA: 900 mcg/day
Same
Sulfur
Component of amino acids methionine and cysteine, which are essential for protein synthesis. It’s also part of vitamins such as thiamine and biotin, and plays a role in the synthesis of glutathione, a major antioxidant. Sulfur is crucial for detoxification processes in the liver and helps maintain the structure of proteins and enzymes.
Protein-rich foods such as meat, fish, eggs, legumes, and nuts
No established RDA/AI, generally obtained through dietary proteins
Sodium
Essential for maintaining fluid balance, nerve transmission, and muscle function. It regulates blood pressure and blood volume and is involved in the active transport of nutrients and other substances across cell membranes. Sodium is crucial for proper electrical signaling in the nervous system and for muscle contractions.
Salt, seafood, and certain vegetables
AI: 1,500 mg/day
Same (if you consume more than that, you can take more potassium to balance it)
Chromium
Enhances the action of insulin, a hormone critical for the metabolism and storage of carbohydrates, fats, and proteins. It plays a role in regulating blood sugar levels by improving insulin sensitivity. Chromium is important for energy production and may influence lipid metabolism and body weight management.
Broccoli, grape juice, whole grains, meat, and brewer's yeast
AI: 35 mcg/day (men), 25 mcg/day (women)
200 to 400 mcg a day
Manganese
Cofactor for several enzymes involved in metabolism, bone formation, and antioxidant function. It’s essential for the metabolism of carbohydrates, amino acids, and cholesterol. Manganese also plays a role in the synthesis of connective tissue and in the functioning of the immune system and brain.
Whole grains, nuts, leafy green vegetables, tea, and certain fruits like pineapple
AI: 2.3 mg/day (men), 1.8 mg/day (women)
Same
Molybdenum
Cofactor for enzymes involved in the metabolism of sulfur-containing amino acids and the detoxification of harmful compounds such as sulfites. It’s essential for the breakdown of drugs and toxins in the liver and helps in the conversion of purines to uric acid, aiding in nitrogen metabolism.
Legumes, grains, nuts, and certain vegetables like leafy greens
RDA: 45 mcg/day
Same
