Supplements can pack a lot of promise in their packaging, like stronger bones, more energy and better sleep. And that’s all without the hassle of multiple trips to the produce aisle, food prep or the lingering smell of fish. (You know, for those omega-3 fatty acids.)

The idea that a capsule or powder can offer so much nutritional value has led many people to ask their doctors: When, if ever, is a supplement a better source of nutrition?

Shannon Pan, MD

Most curious patients, though, aren’t usually looking for a definitive verdict, says Shannon Pan, MD, a primary care and lifestyle physician at Inspira. 

“They’re trying to understand whether what they’re taking is actually helping them,” she says. “The challenge is knowing when a supplement is useful – and when it isn’t doing what people expect it to do.”

Here’s how that plays out across 4 nutrients people ask about most.

Protein: Don’t trust the headlines

Protein advice has shifted dramatically over the years, and that’s left many people unsure whether they’re getting enough – or far too much.

The baseline recommendation is about 0.8 grams of protein per kilogram of body weight, says Kevin Furlong, DO, medical director of endocrinology, diabetes and metabolism and nutrition services at Jefferson Health.

But that number isn’t one-size-fits-all. Needs tend to be higher for older adults, people who strength train regularly and those losing weight quickly.

“When calorie intake drops significantly, protein intake can drop as well,” Furlong says. “That increases the risk of muscle loss.”

That’s often the case with people using GLP-1 weight-loss medications. When overall calories shrink, protein can fall with them, even if someone thinks they’re eating well, says Pan. Still, she cautions against protein-loading. 

“I’m often more concerned about patients not getting enough fiber and other nutrients than about protein deficiency,” she says.

Animal and plant-based foods both contribute to protein intake, but doctors emphasized choosing sources that also offer additional nutritional value, such as Greek yogurt, cottage cheese, beans, nuts, eggs and fish. 

Protein powders or creatine may make sense in certain situations, Pan says, particularly for people doing intense strength training or struggling to meet needs through food. But underlying conditions, especially kidney disease, can make excess protein risky.

And despite what fitness culture suggests, timing isn’t critical. “You don’t need to consume protein immediately before or after exercise,” Pan says. “As long as you meet your daily needs within about a 24-hour window, you’re likely getting the benefit.”

Vitamin D: An exception to the food-is-best rule

Both doctors say vitamin D supplements are often needed. 

Kevin Furlong, DO

“It’s hard to get in sufficient amounts from food,” says Furlong. “And many people are deficient, especially during the winter months or if they avoid sun exposure.”

Still, more isn’t automatically better. Furlong notes that people who already have adequate vitamin D levels don’t benefit from supplements. 

How to tell? Testing can clarify need, but access isn’t always simple. Unless there’s a clear medical reason such as osteoporosis, malabsorption conditions or a documented deficiency, insurance often won’t pay for testing, Pan says. 

While foods like fatty fish, fortified products and egg yolks are vitamin 

D-rich, she says diet alone is rarely enough to correct a deficiency. That’s why it’s one supplement she regularly discusses with patients, usually as a daily vitamin D3 pill. 

Calcium: Enough matters. More doesn’t.

Calcium plays a central role in bone health and becomes especially important for women as they age. For most adults, the recommended daily intake falls between 1,000 and 1,200 milligrams. The difficulty, says Pan, is that many people don’t know how much calcium they’re already getting from food.

Blood tests aren’t especially helpful. Blood calcium levels don’t necessarily reflect whether someone is getting enough of it through diet, she says.

Calcium supplements are most commonly available as calcium carbonate or calcium citrate. The right form can depend on factors such as digestion and whether supplements are taken with food, says Furlong.

More important than the form, he says, is why you’re using the supplement. 

“If you’re close to getting enough from food but not quite there, adding a supplement to bridge the gap is reasonable,” Furlong says.

But taking more calcium than you need isn’t a good idea, he says. Higher supplemental calcium levels could lead to a small increase in cardiovascular risk.

Both doctors say food is the preferred way to increase calcium intake. Leafy greens, almonds, edamame, salmon and fortified foods are calcium-rich choices. Fortified foods such as juices and cereals can also help boost intake.

“With those foods,” Pan adds, “you’re often getting additional nutritional components along with the calcium.”

Fiber: The gap many people don’t see

Fiber is one of the clearest examples of the gap between nutrition guidance and real life. 

“Adequate fiber intake is associated with lower rates of heart disease, cancer and overall mortality,” Furlong says. “But many people don’t come close to recommended levels.”

General guidelines suggest about 25 grams of fiber daily for women and roughly 38 grams for men. But there isn’t a blood test that shows whether someone is getting enough, Pan says. Instead, enough is usually inferred from diet – whether meals regularly include fruits, vegetables, whole grains, beans and legumes – and from digestive patterns over time.

Supplements can be helpful but also come with warnings, says Pan, noting that gastrointestinal problems often occur when people switch from very low fiber intake to a concentrated supplement dose without increasing hydration or allowing their bodies time to adjust. 

“That’s where I see bloating, cramping or constipation,” Pan says. “And very often, hydration is a major part of the issue.”

Instead, she suggests incremental diet changes to increase fiber intake. 

“If I can help someone add one or 2 higher fiber foods consistently,” says Pan, “that’s meaningful.”