Should You Take L-Carnitine Supplements on a Keto Diet? An Evidence-Based Review

Should You Take L-Carnitine on a Keto Diet? A Science-Based Guide

The ketogenic or "keto" diet has surged in popularity in recent years as a way to lose weight and improve health. This very low-carb, high-fat diet aims to get the body into a state of ketosis for fueling the brain with ketones instead of glucose.

But properly following a keto diet requires diligence. Supplements like L-carnitine are sometimes suggested as a way to enhance fat burning and make keto dieting easier.

This comprehensive guide covers the science behind using L-carnitine supplements on a keto diet and helps you decide if it could be beneficial for your needs.

What is L-Carnitine?

L-carnitine is a naturally occurring amino acid derivative found in nearly all cells throughout the body. It plays an essential role in shuttling long-chain fatty acids into the mitochondria to be burned for energy.

Because it transports fats, L-carnitine is sometimes referred to as a “fat shuttle”. Supplement manufacturers market L-carnitine capsules and powders claiming they enhance weight loss and fat burning.

L-Carnitine’s Role in Ketosis

One of the goals of a ketogenic diet is to shift the body into using primarily fatty acids and ketones rather than glucose for fuel. This metabolic state of ketosis occurs when carb intake is very low, generally below 50g per day.

L-carnitine assists the process of fat breakdown for energy by carrying fatty acids to where they are burned in the mitochondria. This has led some to believe that taking L-carnitine supplements can enhance ketosis on a keto diet by shuttling more fat into the cell “furnaces”.

Does Science Support Using L-Carnitine for Keto?

While the proposed mechanism makes sense in theory, what does the actual science say about using L-carnitine supplements on a keto diet?

Unfortunately, most research to date does not show a clear benefit of L-carnitine administration for fat loss, weight reduction, or improved metabolism in humans eating a ketogenic diet.

A 2020 meta-analysis in the journal Obesity Reviews examined 14 controlled trials on L-carnitine supplementation. They found carnitine did not significantly increase weight loss compared to placebo when looking at the evidence as a whole.

A 2019 study in the Annals of Nutrition and Metabolism also showed 2000mg per day of L-carnitine for 12 weeks did not improve body composition or metabolic parameters in women following a low-carb Mediterranean diet.

Potential Minor Benefits of L-Carnitine for Keto

While dramatic fat burning or weight loss have not been demonstrated, minor benefits seen in some studies include:

• Mild improvement in fat mass
• Enhanced fatty acid oxidation during exercise
• Lowered fatigued and improved energy
• Reduced muscle soreness after exercise

These modest effects were mostly seen at higher doses of 2-4 grams per day taken consistently. Such high amounts would be difficult to get from food alone.

L-Carnitine Food Sources on Keto

For those eating a well-formulated ketogenic diet, getting sufficient L-carnitine from natural food sources is preferred over relying on a supplement.

The highest dietary sources of L-carnitine are:

• Red meat like beef, lamb, pork
• Poultry like chicken and turkey
• Fish like salmon, cod, tuna
• Dairy products
• Tempeh
• Avocado
• Asparagus

A 3-4 ounce serving of beef, poultry or fish provides 25-80mg carnitine. Even non-meat sources like avocado and asparagus have about 1-6mg per serving.

Following a well-formulated ketogenic diet that includes sufficient protein should provide at least 60-300mg carnitine from food intake without supplementation.

Who Might Benefit from Carnitine Supplements?

While L-carnitine supplements are likely unnecessary for most doing keto, there are a few situations where they could be beneficial:

• Strict vegetarian or vegan keto - since red meat is the highest source
• Elderly individuals - endogenous carnitine synthesis declines with age
• Kidney disease - impairs carnitine reabsorption
• Genetic carnitine deficiency disorders (rare)

For these groups unable to get sufficient intake from diet, a supplement may prevent potential deficiency. However, doses higher than 500-1000mg per day are still not clearly justified by research for performance enhancement.

Are There Side Effects of L-Carnitine Supplements?

L-carnitine is considered very safe at moderate doses found in food and most supplements. The following side effects may occur with high doses:

• Nausea
• Vomiting
• Heartburn
• Diarrhea
• Cramping
• Fishy body odor

Start low around 500mg once or twice daily and increase slowly if needed to improve tolerance. People with seizures, thyroid disorders, or taking blood thinners should use carnitine supplements with caution.

The Bottom Line: Should You Take L-Carnitine on Keto?

Current evidence does not support L-carnitine supplementation as necessary or tremendously beneficial for the average healthy person eating a well-formulated ketogenic diet.

Natural food sources of L-carnitine from animal proteins and some plant foods are sufficient for most people. Supplements may provide modest additional benefits for fitness, energy, and muscle soreness at higher doses.

Certain conditions like vegetarian keto, poor meats intake, and deficiencies may warrant short-term use of L-carnitine supplements after consulting your doctor. But supplements likely provide minimal advantage for fat loss for the majority following a keto diet.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.