Recently, a friend started to have lots of small bruises all over her body. She was concerned, and noted that the bruising started after she had been eating a low carb diet for a couple of months. Another friend began waking up in the night with severe leg cramps. Again, she noticed that this started to happen after several weeks of low carb dieting. Both women asked if I thought their symptoms could be related to their new low carb eating plans.
It seems lots of people are on low carb diets these days. Lots of other people are considering it. So, what's the deal with low carb diets from a dietitian's perspective?
Carbohydrates Function as Fuel
It's a basic fact of human physiology that the brain and muscles prefer glucose, or sugar, for fuel. Glucose comes from the breakdown of carbohydrate into its simpler components. So, we need to eat carbohydrate in order to function at our very best. Sugary foods not withstanding, carbohydrates come from grains, starchy vegetables, fruit, and dairy products, which contribute essential nutrients to our diets. Grains contribute many B vitamins as well as fiber; starchy vegetables are high in vitamin A & C as well as fiber; fruit is our best source of vitamin C as well as potassium; and dairy products provide calcium and vitamin D. What happens when we miss out on those basic nutrients?
A lack of vitamin C will cause us to bruise easily, like my first friend. We might also notice that our gums start to bleed. This is because vitamin C is essential for collagen formation, and collagen is the substance that literally helps hold our teeth inside our gums. In the case of my second friend, leg cramps are associated with a lack of potassium.
So...what if we just take a vitamin supplement and stay on a low carb diet? This might seem like a good idea, but it probably isn't. If you're on an eating plan that is causing you negative health consequences, you're on an unhealthy diet. The point of changing your eating habits is to improve your health, not just to reduce your weight. If your body weighs less, but is unable to function well due to missing vitamins or minerals, you are in a state of malnutrition.
Additionally, there are no good long-term studies showing how the well the ketogenic diet compares to other diets. How does it affect long-term risk of cancer or heart disease, for example? As stated in a Harvard review by T. H. Chan, “a ketogenic diet has been shown to provide short-term benefits in some people including weight loss and improvements in total cholesterol, blood sugar, and blood pressure. However, these effects after one year when compared with the effects of conventional weight loss diets are not significantly different”.
Healthy Carb Intake
What to do, then? Focus on eating to improve your overall health. A diet that is moderate in all the macronutrients (carbs, fat, & protein) promotes satiety and allows us to get all the vitamins & minerals we need to function at our best. When we eat well, we have more energy for physical activity. When we're physically active, we burn more energy, and our cardiovascular fitness is increased at the same time. Eating well and exercising becomes a positive cycle, improving our physical endurance, our focus, & our mood, as well as our ability to burn the energy we eat for fuel. The bottom line: a healthy diet includes a moderate amount of carbohydrate.