U.S. consumers spend some $60 billion a year on nutritional supplements, which range from multivitamins to digestive aids to alleged muscle-builders and age-defiers. That’s about $175 per capita — a lot of dough, especially considering that many supplements offer little in the way of evidence-based studies (that is, peer-reviewed science) demonstrating efficacy.

Supplements can bring benefits, particularly for seniors and others with nutritional deficiencies. But which ones work, and for whom? UCHealth Today did some homework and caught up with Erin “Wren” Cahoon, a dietitian who works with a variety of outpatients at UCHealth University of Colorado Hospital on the Anschutz Medical Campus, for a rundown of a few common supplements.

First, a couple of points that apply broadly. Dietary supplements are not U.S. Food and Drug Administration-approved, which means their powers may be overstated in ways FDA-approved drugs are not. Cahoon recommends supplements that have been third-party tested by organizations such as NSF and USP, which can lend assurance regarding dosage and purity (supplement labels will bear their logos). And, with occasional exceptions we’ll talk about, a balanced diet with a variety of fruits, vegetables, beans, nuts, seeds, whole grains, and lean proteins (Cahoon is a fan of the Harvard Healthy Eating Plate as a general guide) can ease or erase the need for supplements.

Further, we’re sticking to common nutritional supplements, and so, we’re leaving purported anti-aging supplements (such as alpha-lipoic acid, astaxanthin, CoQ10, curcumin, EGCG, fisetin, L-theanine, NAD+, NMN, quercetin, and theanine) and possible muscle-builders (such as beta-alanine, betaine, carnitine, creatine, DHEA, and glutamine) for another day.

Here is detailed information about health benefits or lack of proof related to these common nutritional supplements:

• Ashwagandha
• Calcium
• Collagen
• Fish oil
• Green powders
• Iron
• Magnesium
• Multivitamins
• Prebiotics
• Probiotics
• Protein powder
• Psyllium
• Vitamin B12
• Vitamin D

Ashwagandha

This Ayurvedic medicine mainstay and social media sensation, derived from a tropical and subtropical evergreen, is technically an adaptogen — something that boosts one’s resilience to stressors. Indeed, studies have shown it to reduce stress and, potentially, improve sleep quality. Purported positive impacts on fertility and athletic performance are less clear.

“It’s usually safe to use, except I recommend against it if you have an autoimmune condition, because one of the things ashwagandha can do is boost your immune system,” Cahoon says. “That sounds great, but if you have an autoimmune condition, we don’t want it to boost the part of the immune system that’s attacking your body.”

It’s also not recommended during pregnancy, breastfeeding or prior to surgery. [Return to menu]

Calcium

A quick perusal of the federal dietary guidelines shows that it can be a challenge to keep up on calcium. Recommended amounts vary, with children ages 4 to 8 and adults from 19 to 50 at 1,000 milligram-per-day range, growing teens at 1,300 milligrams, and women over 50 and everyone over 70 at 1,200 milligrams.

It takes quite a bit of dairy and other calcium-rich foods to get there: A cup of milk (or fortified almond or rice milk) has 300 to 450 milligrams of it, a cup of nonfat yogurt close to 500 milligrams, an ounce-and-a-half of cheese anywhere from 115 to 485 milligrams, and a cup of cooked spinach 245 milligrams. Fortified tofu, sardines, and certain other greens can contribute also, but the reality is, calcium supplements can be a good idea – in particular for postmenopausal women.

“After menopause, women are at a higher risk for osteoporosis, so making sure you’re getting enough calcium is important, and it’s hard to get it all from diet alone,” Cahoon says. [Return to menu]

Collagen

Collagen supplements gain popularity with age because, as we age, we produce less collagen, and with that comes wrinkles that serve as unpleasant reminders of our advancing age. But collagen’s role in the body goes much further.

There are actually 28 known types of collagen, the first five being most common: Type I, is found in skin, bone, and ligaments; type II in cartilage, type III in muscles, arteries, and organs; type IV in the basal lamina that supports cells inside and outside the body; and type V on cell surfaces, hair, and the placenta. So, if you’re supplementing collagen, the type matters. For example, some studies have shown that type 1 collagen improved wrinkles and skin elasticity among women; others have found that type II collagen helped reduce symptoms of osteoarthritis.

One challenge with collagen studies is that vitamin C — itself a supplement — is critical in building the many collagen-based structures in the body, and vitamin C is added to most collagen supplements used in research.

“So, when they’re showing that, hey, these collagen supplements are great for our skin, was it actually the vitamin C that was doing it? We can’t really tease those out,” Cahoon says. “I would actually say what’s best for your skin health is getting plenty of vitamin C-rich foods, if that was your aim for collagen.” These include cantaloupe, bell peppers, chili peppers, broccoli, citrus fruits, kiwi, and dark leafy greens. [Return to menu]

Fish oil

If you’re not eating fish two to three times a week, a fish oil supplement is a great source of DHA, a type of omega-3 fatty acid, Cahoon says. Vegans can find DHA supplements based on algae, too, she adds.

Fish oil lowers triglycerides, a bloodstream fat linked to heart disease, and it may help prevent dementia or Alzheimer’s disease. A preprint (yet to be peer-reviewed) study of more than 400,000 people in Great Britain found fish oil supplementation to lower genetic predisposition for producing LDL (“bad”) cholesterol and triglycerides while boosting that of HDL (“good”) cholesterol. However, others haven’t found conclusive evidence that fish oil lowers high cholesterol, and it may increase LDL, so people taking fish oil should have their LDL cholesterol monitored, Cahoon says. [Return to menu]

Green powders

Green powders, a.k.a. powdered greens – another social media phenomenon – purport to pack the benefits of helpings of vegetables into a couple of pills.

“For an extra little kick of nutrition, they’re not going to hurt you,” Cahoon says.

But she suggests spending the money on actual vegetables instead. Part of it has to do with the challenge in tracking exactly what’s in a powdered green – both in terms of the vegetable inputs and the additives and sweeteners that may come into play.

“It depends on the greens they’re putting in, right? Every vegetable is going to have a bit of a different nutritional profile and a different effect on the body,” she said. “And you should always check the ingredients list to make sure there’s nothing weird in there.” If you are unsure about a specific ingredient, ask a dietitian about it. [Return to menu]

Iron

Iron supplements aren’t typically necessary except for those whose low iron levels can lead to anemia: young children, pregnant women and those with heavy menses, and older people — particularly ones regularly taking aspirin and seniors over 80.

“I don’t think it necessarily makes sense to supplement just because you’re one of those people,” Cahoon says. Just be aware that you’re at high risk, and get screened for iron deficiency, especially if you have symptoms like being fatigued all the time.”

Note that, if you’re taking an iron supplement, there’s evidence that taking it every other day boosts absorption. [Return to menu]

Magnesium

Magnesium supplements are also having their social-media moment, where benefits such as better energy and improved mood get touted. The science there is inconclusive, as with magnesium supplements for leg cramps, insomnia, and dementia. Those who eat legumes, nuts, seeds, whole grains, and leafy greens should be getting enough magnesium without supplements, and it’s in fortified cereal, milk, and yogurt also. But perhaps half of U.S. residents don’t get enough magnesium – especially men over 70, those with gastrointestinal diseases, and those with type 2 diabetes.

Magnesium may help protect from migraine headaches and help treat them once they happen. Keep in mind, though, that in in large doses, magnesium is a laxative (think “milk of magnesia”), Cahoon says. That’s good, but only if you’re constipated. Note that magnesium glycinate is a form of magnesium that’s least likely to cause this effect, she adds. [Return to menu]

Multivitamins

These are the most common U.S. supplements, and, while safe, they’re not needed for those with balanced diets, Cahoon says. There’s no evidence that they benefit longevity or otherwise improve overall health among those who aren’t otherwise vitamin-deficient, and the U.S. Preventative Task Force doesn’t recommended multivitamins for the prevention of cardiovascular disease or cancer, either.

“Broadly speaking, we should get our nutrition from our food first,” Cahoon says. “Yes, there are going to be medical conditions where that changes. But for the broader population, there’s no need to take a multivitamin.” [Return to menu]

Prebiotics

Prebiotics are fiber and fiber supplements that feed healthy gut bacteria. Cahoon is a fan of these supplements, which include inulin/chicory root, fructooligosaccharides (FOS), psyllium (more on this below), and partially hydrolyzed guar gum (PHGG). She’s not alone in her prebiotic enthusiasm. In addition to improving gastrointestinal wellbeing of the general population, there are indications that probiotics reduce systemic inflammation and potentially reduce the risk of colorectal cancer, irritable bowel symptoms, and even help those with autism spectrum disorder.[Return to menu]

Probiotics

These are a much bigger business that prebiotics, but they’re less popular among some health professionals. The American Gastroenterological Society doesn’t recommend probiotics for most digestive conditions; the National Institution of Health’s Office of Dietary Supplements’ rundown of conditions probiotics may effect shows mostly inclusive results.

Complicating matters, Cahoon says, is that “probiotics” is an umbrella term for many bacterial strains that support a healthy gut in different ways.

“It’s kind of like me saying, ‘Go pick up a vitamin,’” she says. “Just like you would need to know which specific vitamin to take, you also need to know which specific strain of probiotic to take to achieve the intended benefit. A dietitian can provide guidance on which probiotic is best for you.”

That’s especially true if your gut mircobiome needs some help, such as after taking antibiotics. But in general, Cahoon says, a good way to maintain a healthy gut biome is to get enough fiber through the foods you eat or prebiotics. [Return to menu]

Protein powder

The average adult needs 0.34 grams of protein a day per pound of body weight (0.75g per kilogram) – roughly 50 grams a day for a 150-pound person. That’s about what a six-ounce chicken breast contains. Protein needs change with activity (athletes and those building muscle in weight rooms need about 50% more) and, perhaps counterintuitively, with age.

That’s because the body undergoes muscle decline at the cellular level – sarcopenia – in our later decades. With that, it’s not as good at using dietary protein to sustain or build muscle. So there needs to be more of that protein coming in – akin to the amounts athletes and gym rats need.

There are many ways to get more protein: eating more beans, nuts, fish, egg whites, tofu, and lean meat among them. However, “Protein powders are a wonderful way to get some extra protein in, especially if you’re struggling to eat a ton of chicken breast all the time, right? Because that can quickly get old,” Cahoon says.

She tells people to check ingredients and avoiding the sweetener erythritol in particular, as it may increase risks of cardiovascular events and blood clots.

Note that research shows that consuming more than 0.4 grams of protein per kilogram of body weight in a single sitting (0.18 grams per pound, or about 27 grams of protein for our 150-pounder) becomes ineffective, as the body processes it into sugar for immediate use or into fat. [Return to menu]

Psyllium

Psyllium, found in fiber supplements (Culturelle, Benefiber, Healthy Origins, and Metamucil, among others), is a prebiotic, and it delivers the benefits outlined under “prebiotics” above. It also helps with bowel regularity, particularly among those prone to constipation. Ideally, though, we would take in that fiber through what we eat, Cahoon says.

“Most of us don’t get our fiber needs met, and we should get more fiber-rich foods like whole grains, fruits, vegetables, nuts, seeds, and beans,” she says. “But a fiber supplement can give us a boost, especially if we need digestive support.”

Cahoon’s Fiber Super Smoothie Recipe is one way she boosts her own diet with fiber and food-delivered vitamins. She recommends starting with a half portion or skipping the fiber powder if you’re not used to eating a high-fiber diet. That’s because we need to prime our guts to tolerate more fiber by gradually increasing our fiber intake. [Return to menu]

Vitamin B12

Insufficient vitamin B12, which plays a key role in red blood cell formation and nervous system function, can cause vitamin-deficiency anemia. But unless you’re a vegetarian or a vegan, have a small bowel disorder, or have undergone gastric surgery, the main reason for vitamin B12-related anemia is age. There’s no evidence that vitamin B12 boosts energy or cuts fatigue among those without a deficiency.

Those over 65 produce less intrinsic factor, a glycoprotein the body needs to metabolize vitamin B12, Cahoon says. They’re also more likely to be on metformin for type 2 diabetes or an antacid proton-pump inhibitor (such as Prilosec or Nexium), which also affect vitamin B12 uptake.

Vitamin D

Vitamin D helps the body absorb calcium for bones and teeth that need it. But vitamin D deficiency has also shown to play a role in depression as well as insulin resistance that can lead to type 2 diabetes.

Our bodies produce vitamin D when our skin is exposed to the sun, but as we age, that process get less efficient. So, elderly adults – and older men in particular – can end up with vitamin D deficiency. The Endocrine Society recommends vitamin D supplements for those 75 and older to lower mortality risk, but also for those ages 1 to 18 to avoid rickets and potentially reduce the risk of respiratory infections. Pregnant women and those at a high risk of prediabetes should also take supplemental vitamin D, the Endocrine Society says.

Cahoon adds that vitamin D supplements are also suggested for those with hypoparathyroidism, osteomalacia, and renal osteodystrophy. [Return to menu]