Is a Low-Carb Diet Ruining Your Health?
"Is a Low-Carb Diet Ruining Your Health?
"This is a guest post by Laura Schoenfeld, a Registered Dietitian with a Master’s degree in Public Health
Pregnancy
I recently discussed the role of carbohydrates during pregnancy in an episode of The Ancestral RDs Podcast. The most important reason why women need adequate carbohydrates during pregnancy is to ensure adequate fetal brain development and growth. Another reason is because a high protein diet can be dangerous during pregnancy, and when you cut out carbohydrate as a major macronutrient, you usually can’t help but increase protein as a percentage of calories. Protein intake greater than 25% of calories during pregnancy may lead to decreased mass at birth and increased perinatal morbidity and mortality for the baby.
The Institute of Medicine recommends a minimum of 175 grams of carbohydrates per day during pregnancy, which is 29% of calories on a 2400 calorie diet. Paul Jaminet advises pregnant mothers to restrict protein to about 15% of calories and to obtain 30% of calories as carbohydrates. Chris recommends a moderate carb approach for most pregnant women (except those with any type of diabetes) in his book, Your Personal Paleo Code (published in paperback as The Paleo Cure in December 2014).
Like these other experts, I generally recommend 30% of calories from carbohydrates for my pregnant clients, and also for those who are struggling with fertility. Unless you have diabetes or a serious neurological condition that requires carbohydrate restriction, it’s not worth the risk playing around with a low carb diet when you’re pregnant, and these diets aren’t conducive to fertility for many women either. (If you’re interested in more reasons why carbohydrates can affect fertility, read this great post by Stefani Ruper.)
Athletes
If you’re a professional or recreational athlete who trains hard 4, 5, or even 6 days per week (I hope you’re not doing 7 days per week!) and trying to maintain this level of activity on a low carb diet, you may be doing more harm than good to your health and fitness.
While there are athletes who thrive on a well-planned low carb approach (LeBron James most recently!), there are many others who do not. Each athlete is completely unique in their ability to perform well on a low carb diet, and there’s nothing wrong with testing out the diet to see how it affects your athletic ability.
But if you’ve been trying a low carb diet for months now and your workouts are suffering, your weight isn’t budging (or maybe you’ve even gained weight!), and your recovery time is increasing, you’re probably not the type of person who can handle a low carb diet combined with regular intense physical activity.
I’ve had many clients come to me on a low carb diet who, after switching to a more moderate carb approach, found that their energy and endurance significantly increased, and they were able to make quicker strength gains than before. Many also were able to shed some of the stubborn body fat that they’d been retaining despite eating a low carb diet and training hard, which was a result they didn’t expect!
For my athletic clients, I usually recommend a minimum of 20% of calories from carbohydrate, and depending on the person’s health goals, training schedule, and current issues, I may actually recommend more like 40-50% of calories from carbs.
Again, each athlete is an individual and what works for one person, or even a thousand people, may not work for you. So don’t be afraid to experiment and pay attention to how your diet makes you look, feel, and perform! And don’t hesitate to get help if you need it!
Hypothyroidism and HPA Axis Dysregulation (Adrenal Fatigue)
Hypothyroidism is one of the most commonly cited medical reasons for needing to eat a moderate carb diet. The main reason why carbs affect thyroid function so directly is because insulin is needed for the conversion of the inactive T4 hormone into the active T3 hormone, and insulin is generally quite low on very low carbohydrate diets.
So if you’ve suddenly started developing hypothyroid symptoms on your low carb diet, it’s a pretty good sign that you’d be better off upping the carbs (and getting your thyroid tested if you haven’t already!) For more about how low carb dieting affects your thyroid, listen to this great interview with Chris by Jimmy Moore.
HPA axis dysregulation, also known as adrenal fatigue, is another condition where a moderate carb intake is important for general health. Kelsey and I talked about adrenal fatigue on our first Ask the RD podcast, so listen to it if you’re unfamiliar with this condition. The main hormone that gets dysregulated in adrenal fatigue is cortisol, and cortisol has been shown to increase on a low carb diet. This means that a low carb diet is a potential adrenal stressor in susceptible individuals. Combine that with a stressful job, inadequate sleep, and overexercise, and you’ve got yourself a recipe for adrenal burnout.
So if you have adrenal fatigue, or if your current lifestyle is already high stress in a few different areas, you may want to increase your carb intake until you can get those additional stressors under control, as you may drive yourself into adrenal fatigue by having a chronically elevated cortisol output. Lara Briden has written a great article on the benefits of whole food carbohydrates in lowering cortisol and raising GABA, a calming hormone that is often low in adrenal fatigue patients.
If you’re experiencing symptoms of hypothyroidism or adrenal fatigue, you may be worsening them with a well-intentioned low carb Paleo diet. I recommend working with someone to help you figure out if your diet is indeed making these symptoms worse, and how to change what you eat to better support your thyroid and adrenal health.
Gut Health
One of the less discussed downsides of a very low carbohydrate diet over the long run is the potential for alteration of the gut flora. Chris recently covered this issue in a podcast with Jeff Leach, where they discussed evidence that a very low carb diet can lead to gut dysbiosis and a reduction in the diversity of the gut flora. A lot of the information on this topic is new and not fully understood, but it’s reasonable to believe that when you avoid carbs, you’re also avoiding important prebiotics (i.e. food for your gut flora) like soluble fiber and resistant starch.
These prebiotics are essential for promoting the growth of beneficial gut flora. Without them, your beneficial flora can’t produce as much gut-healing substances like butyrate and other short chain fatty acids, and your microbiome composition may even shift in an undesirable direction. And as Chris would say, you’re only as healthy as your gut is: an unhealthy gut contributes to everything from obesity and diabetes, to digestive illness, to autoimmune disease, to skin disorders.
Those who are doing very low carbohydrate diets, and who simply can’t increase their starch intake for whatever reason, should use prebiotic supplements such as resistant starch-rich unmodified potato starch or FOS powder. However, these products must be incorporated slowly into your supplement regimen, as you can experience severe gas and bloating if too many prebiotics are taken all at once, or if there is existing gut dysbiosis or bacterial overgrowth. In this case, it would be wise to work with someone who can help you get the prebiotics you need while on a very low carbohydrate or ketogenic diet to protect the health of your gut microbiota.
How Many Carbs Do I Need?
To determine how many carbs my clients need to eat in a day to reach their health goals, first I decide what percentage of calories from carbs they’d possibly do best with. As an example from above, a woman struggling with fertility issues may benefit from a carb intake around 30% of calories. I then determine her caloric needs using a calculator like this one. If we determine that her daily needs are roughly 2000 calories per day, 30% of calories from carbs is 600 calories. As there are 4 calories in a gram of carbohydrate, this works out to be 150 grams of carbs per day.
Usually I give my clients a target range to hit depending on their activity levels, and we use these targets to re-evaluate their food diaries and see if they’re hitting their goals. Most of my clients are surprised to learn how much carb-rich Paleo foods they have to eat to get up to 150-200 grams per day! But once they start making a real effort to hit those targets, the health benefits are immediate.
These benefits include weight loss, elevated mood, skin improvements, increased energy, normal menstrual function, more satisfying sleep, and more. It’s so exciting to see what a couple of starchy tubers and pieces of fruit can do for a person’s health when they simply need to eat more carbs!
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good luck!
. But the obvious elephant in the room that keeps getting dismissed is what most people consider a low carb diet. Few people who say that are referring to the gross extremes he keeps citing. When most people say they eat low carb, they only mean they avoid refined sugar, flour, rice and potatoes, then limit (but don't exclude) fruit. 
