At the European Days of the French Society of Cardiology (JESFC 2026), a dedicated session assessed popular nutrition trends and the strength of the evidence supporting their purported benefits. The key takeaway for clinicians is clear: these trends should be approached with caution and nuance.

Three speakers reviewed the latest scientific data on omega-3 fatty acids, ketogenic diets, intermittent fasting, and carbohydrates, underscoring the frequent disconnect between public interest and strong clinical evidence.

François Paillard, MD, cardiologist at the cardiovascular prevention center of Centre Hospitalier Universitaire de Rennes in Rennes, France, addressed the actual role of omega-3 fatty acids in cardiovascular prevention. These include alpha-linolenic acid, found in flaxseed, walnuts, chia seeds, and rapeseed oil, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are primarily found in oily fish and fish oils. Omega-3 fatty acids can be obtained through diet or supplementation.

“A dietary intake of omega-3s, with two fish meals/week including one oily fish, is associated with a modest reduction in cardiovascular events and all-cause mortality,” Paillard said.

In contrast, except in individuals who consume no fish, “low-dose supplementation, around 1 g/d, provides no benefit in terms of cardiovascular disease prevention,” he added.

However, high-dose supplementation presents a different scenario. Several randomized trials have demonstrated the positive outcomes of high-dose EPA administration. This evidence prompted the European Society of Cardiology in its 2025 recommendations to issue a class IIa recommendation to consider omega-3 in the form of EPA 2 g twice daily in combination with statins for high-risk patients with triglyceride levels between 1.5 and 5.6 mmol/L despite statin treatment.

“However, attention must be paid to the risk for atrial fibrillation,” Paillard cautioned. “There is a U-shaped relationship between DHA and EPA intake and atrial fibrillation risk. Risk decreases with dietary intake but increases with high-dose supplementation.”

Ketogenic Diet and Intermittent Fasting

The ketogenic, or low-carbohydrate, diet, which allows unrestricted intake of fats, proteins, and total energy, dates to 1972 under the name of Atkins’ diet.

Criticized in JAMA as early as 1973, it has only one validated indication, drug-resistant epilepsy in children, according to a 2020 Cochrane meta-analysis.

Reviewing the evidence, Claire Carette, MD, PhD, professor, nutritionist, and diabetologist at the European Hospital Georges Pompidou in Paris, France, emphasized that no randomized nutrition trial can be truly double-blind, which is a key limitation.

Reviewing the latest data on the ketogenic diet, she noted that it showed no difference in long-term weight loss compared with other diets and did not increase cardiovascular risk. However, the Mediterranean diet performed better in terms of blood sugar levels than the other diets. She emphasizes that “the problem with all these diets is how people actually follow them over time: a decrease in adherence is consistently observed.”

The Atkins diet leads to reduced fiber intake with a potentially increased risk for colon cancer and warrants monitoring.

Intermittent fasting involves reducing the daily eating window in several ways. Studies published in JAMA Internal Medicine and The New England Journal of Medicine have shown no benefits for weight loss or metabolic parameters in overweight/obese populations.

In patients with diabetes, intermittent fasting may offer cardiometabolic benefits and improve left ventricular ejection fraction. However, these findings warrant cautious interpretation, given the small sample sizes and short study durations, as emphasized by Carette.

According to a 2024 review in The New England Journal of Medicine, only the Mediterranean diet shows cardiovascular benefits, whereas the DASH diet is effective for hypertension. Importantly, “consider the increased risk of eating disorders with all restrictive diets,” Carette said.

Sugar Intake

Kévin Seyssel, a dietitian-nutritionist from Corbas, Lyon, addressed the demonization of sugar in popular discourse. At the JESFC, he criticized “no sugar challenges” and influencers who portray sugar as being inherently harmful.

He reminded the audience of simple recommendations from the World Health Organization, which advises limiting free sugars to no more than 50 g/d for a 2000-kcal diet, and from the French Agency for Food, Environmental, and Occupational Health & Safety, which recommends a daily intake of 30 g/d of fiber.

Beyond these moderate guidelines, Seyssel warned clinicians and patients to be wary of accusatory and guilt-inducing nutritional messages that often lack scientific evidence.

The speakers reported having no relevant conflicts of interest.

This story was translated from Medscape’s French edition.