Kale salads are sprouting up on menus everywhere. You can find massaged kale Caesars and kale pulverized in smoothies. This may not be the health food it seems. A daily dose of raw greens may leave you tired and gaining weight.

Leafy greens have many health benefits; they are a rich source of magnesium, carotenoids and other antioxidants. Greens can reduce sugar cravings and energize us. Almost every long-lived culture makes leafy greens a staple.

According to Richard Kunin, MD, a San Francisco medical doctor,  raw greens however, contain an undesirable long chain wax on their surface. In nature this protects leaves from predators and UV light, but in your body it appears to block fat from being burned. Not only could this leave you plumper than you’ like, but unusually tired.

I studied with Dr Kunin years ago in San Francisco. His patient mix included wealthy women and the “incurable,” who he usually cured. He noticed a recurring pattern in many of his female patients. Despite healthy diets full of salads and lean meats, many were fatigued and unable to burn fat.

Perplexed, Kunin ran blood tests and found abnormal concentrations of a long chain wax unique to some dark leafy greens. This wax can block L-carnitine from transporting fat into cells where it is burned by the mitochondria for energy. It is found primarily on darker heartier greens such as kale, collards and chard but not the delicate leaves of lettuces.

Furthermore, kale is a cruciferous vegetable. Along with raw broccoli, cabbage and others in this family, kale is well known to interfere with thyroid function, another cause of low energy and weight gain. I’ve had many clients complain to me of low thyroid signs, including fatigue and inability to burn fat. A steady diet of green smoothies and raw broccoli is often a contributor.

The solution is simply to cook these veggies. Cooking dissolves the wax and inactivates the thyroid-blocking property in these veggies. Cooking also makes the vitamins in plants more bio-available.  Studies show you end up assimilating more vitamin C when you lightly cook your veggies.  As long as you don’t cook them to death, a light cooking leaves vegetables better for you, and usually better-tasting.

Traditional cultures use a variety of cooking methods to enhancing flavor. In Asia greens, such bok choy, gai lan and pea shoots, are stir-fried, braised or cooked into soups. In Brazil, finely shredded kale is commonly sauteed and served with pork. In the Mediterranean, greens are boiled, drained then topped with lemon juice, fresh pressed garlic and olive oil. In the south collards and mustard greens are boiled with ham hocks. I spent years living in France, Spain, Turkey and Greece, dining on a variety of delicious cooked leafy greens, Fortunately I never saw a kale salad.

If you are not losing the weight you want nor have the energy you’d like, consider cooking your kale.