Nutrition Myths That Just Won’t Die: What the Science Really Says

In today’s information-overloaded world, nutrition myths spread like wildfire—on TikTok, at the gym, and even from well-meaning friends or family. But some of the most popular ideas about food and health are flat-out wrong—or at least wildly oversimplified. As a registered dietitian, I hear them all the time.

Let’s clear the air. Here are seven of the most common nutrition myths—and what science actually says about them.

1. Carbs Make You Gain Weight

The truth: Carbohydrates themselves don’t cause weight gain—excess calories do. In fact, carbs are your body’s preferred energy source. Complex carbs like whole grains, fruits, legumes, and vegetables are rich in fiber and nutrients that support digestion, heart health, and stable energy.

Diets that restrict carbs often cause quick weight loss due to water loss—not fat. Long-term studies show that sustainable weight loss comes from overall healthy eating patterns, not eliminating one macronutrient group.

Better advice: Focus on quality carbs (whole grains, fruit, legumes), eat balanced meals, and manage portions—not carb fear.

2. You Need to Detox After Eating “Bad” Foods

The truth: Your liver and kidneys are your detox system. No juice cleanse, supplement, or celery smoothie can "flush out" toxins more effectively than your own body.

Cleanses may lead to short-term weight loss from calorie restriction, but they often lack protein and fiber, can be expensive, and may leave you feeling fatigued and irritable.

Better advice: Support your natural detox system with fiber-rich plant foods, hydration, regular meals, and plenty of rest—not restriction.

3. Eating After 8 PM Causes Weight Gain

The truth: It’s not when you eat, but how much you eat throughout the day that impacts weight. Late-night eating is often linked to snacking on calorie-dense, low-nutrient foods—not the time on the clock.

Your metabolism doesn’t shut off at night, but if you’re eating out of boredom, stress, or habit, it may lead to unintended overeating.

Better advice: Be mindful of nighttime hunger, build satisfying meals earlier in the day, and aim for balanced, intentional snacks if needed in the evening.

4. Frozen Fruits and Veggies Are Less Nutritious Than Fresh

The truth: Frozen produce is picked at peak ripeness and flash-frozen, preserving nutrients beautifully. In some cases, it may even contain more vitamins than fresh produce that’s been sitting in a warehouse or truck for days.

Better advice: Mix fresh and frozen produce into your routine. Frozen fruits and vegetables are a budget-friendly, convenient, and nutritious option.

5. You Must Drink 8 Glasses of Water a Day

The truth: There’s no one-size-fits-all rule. Hydration needs vary based on your size, activity level, weather, and food intake. Some people need more, some less.

Also, we get water from food (especially fruits and veggies) and other fluids like tea, milk, and soup—not just plain water.

Better advice: Use your body as a guide. If you're thirsty, drink. Your urine should be pale yellow. Increase fluids when active or in hot weather.

6. High-Protein Diets Are Bad for Your Kidneys

The truth: For healthy individuals, there’s no strong evidence that a high-protein diet harms kidney function. The concern mainly applies to people with existing kidney disease, where protein needs should be carefully managed.

In fact, higher protein intake can help with satiety, muscle preservation, and metabolic health—especially as we age or during weight loss.

Better advice: Most adults can safely enjoy a higher-protein diet. If you have kidney concerns, check in with a dietitian or healthcare provider.

7. Natural Sugar Is Always Better Than Added Sugar

The truth: Your body metabolizes sugar from honey, maple syrup, or agave the same way it does from white sugar. While "natural" sweeteners may contain trace minerals, the difference is negligible when consumed in typical amounts.

Added sugars, whether natural or processed, should be enjoyed in moderation—less than 10% of your daily calories, according to health guidelines.

Better advice: Focus on whole food sources of sweetness (like fruit), and enjoy sweeteners mindfully—without falling for health halos.

Final Thoughts

Nutrition doesn’t need to be complicated—but it does need to be accurate. While food fads come and go, science-based guidance stands the test of time. If you're unsure about something you've heard, check your sources—or better yet, ask a dietitian.