Function
Recommended intake
Common supplement dosing
When to take
Vitamin A
Vision, immunity, reproductive health, growth and development
700-1,300 microgram retinol activity equivalents (mcg RAE)
750-3,000 mcg RAE
With a meal or snack containing fat
Vitamin D
Bone health, regulating inflammation, immunity, glucose metabolism
600-800 international units (IU)
400 IU and up
With a meal or snack containing fat
Vitamin E
Immunity, antioxidant protection
15-19 milligrams (mg)
67 mg or higher
With a meal or snack containing fat
Vitamin K
Normal blood clotting, bone health
75-120 micrograms (mcg)
90 mcg and up
With a meal or snack containing fat
When supplementing with other nutrients, such as minerals like magnesium and iron, there are some guidelines to follow to ensure maximum absorption:
Iron
Iron is crucial for health—it forms hemoglobin, a protein in red blood cells that carries oxygen from the lungs to the rest of the body. Iron is also necessary for energy production, growth, hormone synthesis, and neurological development.
Iron needs range from 8-27 milligrams, depending on sex, age, and pregnancy status. Several types of iron are used to treat low iron levels, including ferrous sulfate, ferrous fumarate, and ferrous bisglycinate.
Iron doses in supplements are typically 18-65 micrograms. However, iron doses can be confusing. Many bottles contain elemental and chemical amounts. The elemental amount is usually the smaller number on the bottle. It’s the amount used for dosing and the amount available for your body to absorb.
Iron supplements should be taken on an empty stomach, at least 30 minutes before eating and two hours before taking other medications. They should not be taken with dairy products, calcium supplements, caffeine, high-fiber foods, or antacids.
However, Some people experience gastrointestinal discomfort from iron supplements. If taking iron supplements causes stomach upset, like nausea, they can be taken with a small meal or snack.
Magnesium
Magnesium is a mineral required for blood pressure and blood sugar regulation, nerve function, muscle contraction, and DNA synthesis. It is found in many foods, including vegetables and beans.
Magnesium needs are 310-420 milligrams per day. Magnesium supplements typically provide 100-400 milligrams per serving. Magnesium oxide, magnesium citrate, and magnesium glycinate are common forms of magnesium used in dietary supplements.
Magnesium can be taken at any time of day, with or without food. Some people take magnesium at bedtime, as certain research suggests it can help with sleep.
Omega-3s
The omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) play important roles in your heart, lungs, immune system, and endocrine systems. They also have powerful anti-inflammatory properties and help regulate inflammation in your body.
Though dosing varies considerably depending on the type of supplement, most omega-3 supplements have 180 milligrams of EPA and 120 milligrams of DHA per serving.
Omega-3 supplements can be taken at any time of day, but research suggests that they may be better absorbed with a fat-containing meal or snack. Taking omega-3s with foods can reduce side effects, like nausea and a fishy aftertaste, which some people experience when taking them on an empty stomach.
Several factors impact how vitamins are absorbed. Fat-soluble vitamins are better absorbed with a meal containing fat, while iron supplements are usually recommended on an empty stomach or with a vitamin-C-rich beverage, like orange juice.
Another factor that influences absorption is the form of nutrients used in dietary supplements. Studies show that certain forms of magnesium, such as magnesium citrate, glycinate, malate, and acetyl taurate, are absorbed better by the body than magnesium oxide and magnesium sulfate.
Taking certain foods, drinks, medications, and other dietary supplements with vitamin and mineral products may reduce absorption. Calcium supplements, coffee, and antacids can significantly reduce iron supplement absorption.
Certain medical conditions, such as gastrointestinal conditions like Crohn’s disease and celiac disease, can also make it harder for your body to absorb nutrients from food and dietary supplements.
Not everyone requires vitamin supplements, but they can help people who follow diets low in fruits, vegetables, healthy fats, and proteins. They can also benefit people with certain medical conditions, such as Crohn’s disease, Celiac disease, and diabetes.
People with nutrient deficiencies require supplementation to reach and maintain healthy blood levels of some nutrients.
If you’re unsure whether you would benefit from taking vitamins, speak with your healthcare provider. They can order blood tests and assess your diet and underlying health conditions to develop a vitamin routine that works best for you. They can also advise you on safe intake levels and recommend a dosage that best suits your needs.
When taking supplements, it’s best to have a routine that encourages regular intake, such as taking your vitamins in the morning, afternoon, or evening, depending on the type. Setting a reminder on your phone or using a daily supplement organizer can help encourage you to take your vitamins consistently.
