To reap the most benefits from your wellness routine, it’s important to consume your daily supplements properly. And that’s not always as simple as just remembering to take them.

In certain cases, you should take supplements alongside specific foods in order for them to be best absorbed in your body and ultimately do their job. Here are four popular supplements to take with food—and what specific types of foods to pair them with. 

1. Fat-Soluble Vitamins

Fat-soluble vitamins (which include vitamins A, D, E, and K) are nutrients absorbed along with fats and typically stored in fatty tissues in the body, says Rebekah Blakely, R.D.N., a dietitian for The Vitamin Shoppe.

Given that, it’s no surprise that you should take them alongside food—and particularly food that contains healthy fats. High-fat foods stimulate the release of bile acids in the stomach, which then helps the body absorb the nutrients you’re taking, explains dietitian Sarah Koszyk, R.D.N., author of 25 Anti-Aging Smoothies for Revitalizing, Glowing Skin. 

Just how much do those fats really matter? Get this: One study found that taking vitamin D with dinner (which typically contains more fat) instead of breakfast increased blood levels by about 50 percent. 

Read More: 7 Groups Of People Who Need More Vitamin D

That’s not to say you can’t take your D with a different meal. But it’s wise to ensure that meal contains healthy fats, such as avocado, nuts, seeds, olives, grass-fed butter, or olive or coconut oil.

2. Iron 

Iron is best absorbed on an empty stomach, but doing so might cause stomach cramps or nausea, so taking it with food is typically your better option, Koszyk says. 

Plus, taking iron with foods high in vitamin C, like broccoli, bell peppers, strawberries, or spinach, can increase absorption, Blakely adds.

With that said, you don’t want to take your iron supplement with foods high in calcium (like milk or yogurt). Calcium and iron target the same receptors in your body, so calcium in your food will block the iron from being optimally absorbed, explains dietitian Christine Byrne M.P.H., R.D. 

3. Calcium 

When taking a calcium supplement that specifically contains calcium carbonate (the most common form found in supplements), take it with food to ensure proper absorption and prevent stomach upset, says The Vitamin Shoppe nutritionist Roseanne Schnell, C.D.N.

While any meal will do, consider pairing your calcium with foods that contain vitamin D, which supports calcium absorption, according to dietitian Laura Kunces, Ph.D., R.D. Fatty fish and egg yolks are two solid options.

Read More: 5 Nutrients Other Than Calcium That Support Healthy Bones

Some studies suggest that high-fiber foods may bind to calcium and impair its absorption, while others suggest they may actually aid calcium absorption. Since there’s not a lot of clarity there, Blakely recommends avoiding taking calcium supplements alongside fiber supplements or meals that are super-high in fiber (like three-bean chili). Don’t worry about taking it alongside some veggies, though.

And, of course, don’t forget that bit from before about calcium and iron competing for absorption. Try to avoid taking calcium supplements with high-iron foods, such as leafy greens, meat, or beans.

4. Multivitamins

Multivitamins contain a variety of vitamins and minerals in order to help you meet your overall nutritional needs. Schnell recommends taking your multi with food because the meal increases stomach acid and slows down movement through the digestive tract, supporting proper absorption of all the goodness in your supplement.

Not to mention, many people experience stomach upset after taking a multivitamin on an empty stomach.

Since most multivitamins contain fat-soluble vitamins, make sure your meal contains some fat, like nuts, dairy, or a healthy cooking oil, says Byrne.

That said, vitamin B12, in particular, is better absorbed on an empty stomach, so if you need extra B vitamins (which athletes, people with high levels of homocysteine or risk of heart disease, and the elderly do), Kunces recommends taking a separate B-complex supplement and doing so sans food.