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 |
Because fat-soluble vitamins are stored in your body, you don’t need to consume them as often as water-soluble vitamins. However, because they’re stored in your body, there’s a greater risk for toxicity.
It’s recommended to avoid taking large doses of fat-soluble vitamins unless advised by a healthcare provider, but there are some exceptions to this rule. For example, people with insufficient or deficient vitamin D levels may have to take large doses of up to 50,000 IU per week to increase their levels.
Fat-soluble vitamins are absorbed in the intestine with fat, so it’s recommended that they be taken 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 a critical mineral for the body. 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.
It’s recommended that iron supplements be taken on an empty stomach at least 30 minutes before eating. 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.
Iron supplements should be taken at least two hours before taking medications and should not be taken with dairy products, calcium supplements, caffeine, high-fiber foods, or antacids.
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.
Depending on the type, some vitamins and minerals can be taken at any time of day, with or without food, while others require a meal containing fat for best absorption.
Ask your healthcare provider for advice if you have questions about vitamin intake, including the best time to take your daily supplements.