Several natural supplements with strong scientific support were reviewed last week. In the U.S., dietary supplements are regulated as foods under the Dietary Supplement Health and Education Act (DSHEA) of 1994. Not labeled as drugs, they do not require FDA approval for safety or efficacy before marketing. This allows products to be sold without rigorous testing, and their claims may lack scientific validation. While some supplements may benefit individuals with specific medical needs, use without clear justification can cause harm.

Multivitamins Multivitamins, for example, are widely used to prevent disease and cover nutritional gaps. They remain appropriate for those with malabsorption syndromes, restrictive diets, or diagnosed deficiencies. However, in well-nourished populations, they do not significantly reduce chronic disease risk. Further, excess vitamin A may lead to liver damage, while too much iron can cause gastrointestinal distress.

Vitamin C

A similar outcome occurs with vitamin C. Although regular supplementation may slightly reduce cold duration, it does not prevent them. It also may help smokers or those with poor dietary intake. Still, high doses can cause gastrointestinal discomfort or kidney stones. Another risk is “rebound scurvy,” a deficiency triggered by abruptly stopping high-dose use due to the body’s increased breakdown rate.

Calcium Calcium supplementation is warranted in deficiency, osteoporosis, or in those with high fracture risk. Yet studies show that in healthy older adults, it does not significantly help. In fact, excess calcium may increase risk of kidney stones and interfere with iron, magnesium, and zinc absorption.

Collagen Collagen may help with skin aging or joint concerns, though only modest effects are shown in mostly industry-funded studies lacking long-term data. Although generally safe, supplementation may worsen kidney disease in affected individuals. Further, the hydroxyproline in collagen may raise calcium oxalate stone risk in predisposed people.

Green Tea Extract Promoted for weight loss, green tea extract has limited supporting evidence. Moderate intake via brewed tea may be safe, but high-dose extracts have been linked to liver toxicity, including rare liver failure cases.

Spirulina This nutrient-rich algae is said to boost energy and immunity. Though it supplies protein and micronutrients, broader claims lack scientific support. Further, due to lack of regulation, some products may be contaminated with microcystins, liver-damaging toxins from blue-green algae.

Shark Cartilage Marketed as a cancer remedy due to the myth that sharks don’t get cancer, shark cartilage supplementation lacks scientific support. It may even contain contaminants and contribute to ecological harm.

Red Yeast Rice Containing monacolin K (chemically identical to lovastatin), red yeast rice may lower LDL cholesterol. So, it could help statin-intolerant individuals under medical supervision. However, products vary and potential side effects, like statins, include liver damage and muscle pain.

Chromium Marketed for blood sugar control and weight loss, chromium’s effectiveness is doubtful. Its essentiality is debated, as humans produce small amounts. Supplementation is rarely needed and reserved for diagnosed deficiency. But high doses may even harm kidney and liver function.

Garcinia Cambogia Heavily marketed for weight loss, this fruit extract shows little to no benefit. And some cases of liver toxicity have even been reported.

Conclusion Natural does not always mean safe or effective. Many popular supplements lack strong scientific backing and may pose health risks when used without guidance. Consultation with a qualified healthcare provider, such as a registered dietitian, is recommended before beginning any supplement regimen.

About the Author

Patrick Traynor, PhD, MPH, RD, CPT is a registered dietitian and founder of MNT Scientific, LLC, an insurance-based nutrition practice serving South Lake Tahoe and Sacramento, CA; Minden, NV; and Ashland, OR. Virtual appointments are also available via telehealth. To request a consultation, visit MNTScientific.com. For inquiries, email patricktraynor@patricktraynor.com.