Vitamins and other dietary supplements are nothing new, but their increasing popularity has given rise to some questions about how they can be most effective, as well as how to avoid drug interactions and other common side effects.
Can you take a multivitamin on an empty stomach, or should you make sure you eat first? Is it okay to have iron with breakfast? Can you have a calcium supplement at the same time as you take your daily blood pressure medication for convenience, or could it cause a risky drug interaction?
More than half of adults (58.5 percent) and a third of children in the United States said they’d taken a dietary supplement in the previous 30 days, according to a report released by the Centers for Disease Control and Prevention (CDC) in April 2023, so information about optimal ways to supplement is important.
It does matter when you take a dietary supplement. Smart timing can make a difference in how well your body absorbs the nutrients in your supplement, says Doug Cook, RDN, the co-author of Nutrition for Canadians for Dummies and the host of the Pursuit of Health podcast. It can also let you side-step medication absorption problems that can arise if you take some supplements with certain drugs. (That’s why you should always tell your doctor which supplements you’re taking.)
“It’s easy to correct deficiencies and improve health just by being consistent in how you take a supplement,” Cook says. Here’s some helpful advice about several common dietary supplements, courtesy of Cook and other nutrition experts.
A Daily Multi-Vitamin
Timing tip: Any time of day is okay, but it’s beneficial to take them with food.
It’s okay to take your daily multi whenever you want, Cook says. But taking it with a meal or snack has two advantages. First, having food in your stomach could prevent getting an upset tummy and nausea, reports the Cleveland Clinic. And secondly, if whatever you eat has any dietary fat, that can help facilitate the absorption of the fat-soluble vitamins your multi contains.
Vitamins including A, D, E, and K are fat-soluble, and research published in September 2022 in Nutrition & Metabolism found that these play an important role in an array of body functions, including immune regulation, and vision, bone, and mental health.
Similarly, washing down your multi with a glass of water not only makes it easier to swallow, it also aids the breakdown of water-soluble vitamins in it, according to the Cleveland Clinic.
While many people make a habit of taking their vitamins first thing in the morning, you don’t have to pair your multi with breakfast. Lunch or dinner are just as good.
“What matters is taking supplements consistently, in a way that works for you,” Cook says.
And your multi doesn’t have to be a tablet. Gummies, liquid vitamins, or powders that you mix with water, sub-lingual drops and dissolvable pills that melt under your tongue and even sprays are also good options, according to Cook. Just check the nutrition facts panel to be sure your chosen form provides the vitamins, minerals, and other nutrients you want, at the dose you need.
Individual Water-Soluble Vitamins: The Bs and Vitamin C
Timing tip: Try taking B12 in the morning and spread out your vitamin C over the day.
The wide range of B vitamins – including thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folic acid (B9), and cobalamin (B12) – and vitamin C, all require water for absorption. So be sure to take them with a full glass of H2O.
B vitamins are fine to take anytime, but if you take B12, you may want to take it first thing in the morning. Why? This particular B vitamin plays a role in energy metabolism, so has gained a reputation as an athletic performance and endurance booster. These are not claims, however, that have been backed up by research, unless you have a B12 deficiency, according to the National Institutes of Health (NIH). Still, Cook says that it may be worth experimenting with taking it in the morning, instead of at night, in case you do experience an increase in energy.
As for vitamin C, because the human body cannot synthesise this nutrient, the best source is to get it from your diet, according to the NIH. Water-soluble vitamins like C do not stay around in your system for a long time, so it may be helpful to divide your dose and take smaller amounts of C two to three times a day instead of all at once, giving your body more time to absorb the nutrient the way it would from food, suggests the Icahn School of Medicine at Mount Sinai in New York City. Just be careful not to overdo it – taking more than 1,000–2,000 mg per day can lead to stomach upset and diarrhoea, according to the NIH.
Fat-Soluble Vitamins: Vitamins A, D, E, and K
Timing tip: Take with a meal or snack containing fat.
Having some fat in your stomach when you take fat-soluble vitamins is essential for absorption, Cook says – although it may depend on the specific vitamin. A study published in the American Journal of Clinical Nutrition in November 2019 found that you can eat fat up to 12 hours after taking vitamin E and still improve its bioavailability.
“Fat helps with the body’s secretion of bile, which you need for maximal absorption,” he says. The specific amount of fat needed varies depending on the vitamin: Some past research suggests that around 10 grams (g) of fat may be ideal for absorbing vitamin D.
Some good options for healthy fats include a little nut butter, a handful of almonds, or a half-tablespoon of olive oil, says Cook. “Any meal or snack with fat in it will be helpful,” he says. “You wouldn’t want to take a fat-soluble vitamin with black coffee and a bowl of cereal with skim milk, but just adding toast with peanut butter would provide the needed fat.”
While your body needs vitamin D in order to absorb calcium, you do not have to take these two supplements at the same time to get benefits, he adds. “Calcium and D are often combined in one supplement for convenience,” he says. “But your body stores some D in your fat tissue, and there’s some in your plasma.”
Timing tip: Take most calcium supplements with food, but not more than 500–600 mg at a time. Be careful taking calcium with some medications.
Take most types of calcium supplements (such as calcium carbonate) with a meal, not on an empty stomach. According to the Bone Health and Osteoporosis Foundation, stomach acid secreted to digest food will break down calcium supplements for better absorption. The convenient exception: You can take calcium citrate supplements on an empty stomach – it will get absorbed even if you haven’t eaten anything, the group notes.
But here’s the catch about the calcium-with-meals rule: Your body absorbs calcium most efficiently in 500 mg doses or less, according to the NIH, and that includes any calcium in the food and drinks you’re having. “If you need more than that amount from supplements, be sure to split it up and take it at different times of day, several hours apart,” Cook says.
If your breakfast tends to feature dairy products or fortified cereal or juice, you may want to move your calcium supplements to lunch, dinner, or another time of day to make the most of them. That’s because 8 ounces of plain low-fat yogurt contains 448 mg of calcium, and 8 ounces of low-fat milk or fortified orange juice each deliver 300 mg.
Calcium supplements can interfere with the absorption of a variety of medications, so be sure to talk the subject over with your doctor if she prescribes a new medication, if you start using calcium, or if you’ve never discussed it before.
Among the drugs of concern are: antibiotics called fluoroquinolones (ciprofloxacin [Cipro], levofloxacin [Levaquin]) and tetracyclines (doxycycline [Bio-Tab, Doryx, Doxy-Caps], tetracycline hydrochloride [Achromycin V, Panmycin, etc.]), according to the non-profit medication-education organisation Institute for Safe Medication Practices (ISMP). The group recommends that you talk to your doctor about the best timing for these medications if you take calcium, but in general suggests taking these antibiotics two hours before or six hours after a calcium supplement.
Calcium could affect levels of seizure-controlling drugs like phenytoin (Dilantin), carbamazepine (Carbatrol, Equetro, Tegretol, Petiole), phenobarbital, and primidone (Mysoline), according to the ISMP. In general, taking the drug two hours or more before or after your calcium supplement may help, the group notes.
Calcium could hinder absorption of the synthetic thyroid hormones levothyroxine (Synthroid, Unithroid, others) and liothyronine (Cytomel), and thyroid extract supplements, according to the Indiana-based Beacon Health System. Wait at least four hours before or after a dose of these drugs to take a calcium supplement.
Doctors often prescribe calcium and vitamin D supplements to people with osteoporosis, along with bisphosphonate drugs such as alendronate (Fosamax, Binosto), ibandronate (Boniva), and risedronate (Actonel, Atelvia). But taking them together could reduce drug absorption. Instead, take the supplements at least 30 to 60 minutes after your bisphosphonate, the ISMP advises. Check with your doctor for best timing.
Timing tip: Take iron with a vitamin C–rich food or beverage for best absorption. Add food to combat queasiness, or take at bedtime. Be careful with some drugs.
If your doctor has recommended an iron supplement, you may be hearing conflicting advice about the best way to take it. While it’s best on an empty stomach, calcium, multi-vitamins, high-fibre foods like whole grains, and even caffeine can interfere with absorption, the MedlinePlus reports. Having some vitamin C, such as a glass of orange juice or a vitamin C supplement, with your iron supplement will aid absorption, per research published in Communications Biology in August 2018. And that “empty stomach plus iron supplement” advice can lead to nausea. In that case, it’s okay to take it with some food (like a vitamin C–rich orange, grapefruit, tangerine, or some kiwi fruit), he says. Or try having your iron at bedtime; you probably won’t notice mild tummy discomfort while you sleep.
Be careful with medications: Iron can interfere with the absorption of levothyroxine (Levothroid, Levoxyl, Synthroid, Tirosint, and Unithroid) drugs; consult your doctor and be sure not to take iron within at least four hours of this medication, the Office of Dietary Supplements advises. It may also interfere with some antibiotics, like tetracyclines and penicillin. Meanwhile, acid-reducing drugs including proton pump inhibitors such as lansoprazole (Prevacid) and omeprazole (Prilosec) and H2 receptor blockers cimetidine (Tagamet), famotidine (Pepcid), and nizatidine (Axid) could reduce iron absorption, reports MedlinePlus. Wait at least two hours before or after an iron supplement to take these drugs, the University of Michigan health system advises – and again, talk with your doctor if she prescribes these and you take iron.
Other Mineral Supplements: Magnesium and Zinc
Timing tip: Be careful with some medications.
Both magnesium and zinc can interfere with the absorption of fluoroquinolone and tetracycline antibiotics, according to the independent supplement-testing company ConsumerLab.com. Talk to your doctor. The Office of Dietary Supplements suggests having your antibiotic at least two hours before, or four to six hours after these supplements. If you take the rheumatoid arthritis drug penicillamine, wait one hour before or after taking zinc to avoid absorption problems, too, the organisation recommends. If you use bisphosphonate osteoporosis drugs, wait at least two hours before taking magnesium.