Misrepresenting the Evidence on Low-Carb Diets

Recently I found an interesting article about low-carb diets on WebMD. I know that much of the information found online is critical of carb restriction, but I was unprepared for the claims made on this website, which is extremely popular and considered a trusted source by many Americans.

First of all, the article discusses “high-protein, low-carbohydrate diets” and defines “high protein” as 30-50% of caloric intake. Aside from the Stillman diet and perhaps the diets of a few bodybuilders, I don’t know of any other popular low-carb plans that recommend more than 30% of calories from protein. On a 2000-calorie diet, 30%  is 150 grams of protein, and 50% is 250 grams. Most low-carb diets are moderate in protein, although some people may consume higher amounts. This article purports to talk about the risks vs. benefits of high-protein, low-carbohydrate diets, but the “benefits” are glossed over, and several of the statements seem to denigrate carb restriction in particular.

According to Web MD,  high-protein, low-carb diets can cause many health problems:

• Kidney failure  This is untrue in the case of people with healthy kidneys. Although individuals with advanced kidney disease may need to restrict protein, there is no evidence that a high-protein, low-carb diet damages renal function (1).
• High cholesterol  The article states “It is well known that high-protein diets (consisting of red meat, whole dairy products, and other high fat foods) are linked to high cholesterol. Studies have linked high cholesterol levels to an increased risk of developing heart disease, stroke, and cancer.”  First off, low-carb diets don’t always result in elevated cholesterol levels. And in the vast majority of cases, lipid profiles become more favorable in terms of particle size and number, improved HDL to cholesterol ratio, and lower triglycerides, resulting in less risk of cardiovascular disease and stroke. The exception would be people with familial hypercholesterolemia, who may need to limit dietary fat and cholesterol and replace most foods high in saturated fat with items containing monounsaturated fat like olive oil. With respect to cancer, older and recent research has demonstrated that it is associated with lower rather than higher cholesterol levels (2,3).
• Osteoporosis  Studies indicate this is not a concern with high protein consumption provided intake of   plants — ie, nonstarchy vegetables — is adequate (4).
• Cancer  It’s irritating to repeatedly read the assertion that low-carb diets don’t provide vitamins, minerals, fiber, and antioxidants. There are loads of micronutrients in animal products, and the vegetables, berries, nuts, and avocado consumed on carbohydrate-restricted diets supply plenty of fiber and antioxidants.
• Unhealthy metabolic state (ketosis)  The information on ketosis in this article was contradictory but predominantly negative. On the one hand, the benefits of ketosis (switching to fat burning, weight loss, reduced appetite) are discussed early in the article, but later:  “During ketosis, the body forms substances known as ketones, which can cause organs to fail and result in gout, kidney stones, or kidney failure.” Where is the evidence for this statement?  Children with epilepsy following extremely low-carb ketogenic diets (about 10 grams of carb per day) were found to be at greater risk of developing kidney stones (5), but as far as I know, this hasn’t been seen in adults following VLC diets that include nonstarchy vegetables and berries. As far as gout, people who already have the condition will need to continue to monitor their uric acid levels, and they would benefit from eating alkalizing plant foods like vegetables in addition to protein and fat. However, there is no evidence that ketogenic diets cause gout, and because this condition is  related to insulin resistance, outcomes may actually improve on a carb-restricted diet.  Finally, there is no evidence that ketogenic diets cause kidney failure; in fact, preliminary research suggests they may actually reverse kidney damage (6).

In the summary, “Is Low Carb Right for Me?” the writer states that carb restriction is dangerous, particularly for those with heart disease, and that low-carb diets don’t allow a high intake of fruits and vegetables. I strongly disagree.  I believe this way of eating is beneficial for people with heart disease for the reasons listed above, as well  as improvements in hyperinsulinemia, hyperglycemia, and hypertension. And there are plenty of plant foods allowed on a low-carb diet. I eat vegetables at every meal, a few servings of nuts a day, berries once a day, and avocado just about every day on my VLC diet. I probably get more vegetables than most people do, along with more fiber and antioxidants.

Although I guess I shouldn’t be surprised, it concerns me that such a highly critical and inaccurate article was published on WebMD.  Perhaps there are even worse articles written on medical sites considered reputable? In my opinion, using scare tactics to discourage people from adopting a carbohydrate-restricted diet is troubling, particularly since this way of eating has had such a positive impact on a significant number of people and has the potential to improve the lives of so many others.

* Although low-carbohydrate diets are safe and healthy for most people, it’s important to speak with your doctor prior to adopting a low-carb diet or making other dietary changes.

References:
1. Friedman AN, et al. Comparative effects of low-carbohydrate, high-protein vs. low-fat diets on the kidney. Clin J Am Soc Nephrol. 2012 Jul;7(7):1103-11
2. Kritchevsky SB, et al. Serum cholesterol and cancer risk: an epidemiologic perspective. Annu Rev Nutr. 1992; 12:391-416.
3. Strohmaier S, et al. Total serum cholesterol and caner incidence in the metabolic syndrome and cancer project (ME-CAN).J Epidemiol Community Health 2011; 65:A302 doi:10.1136/jech.2011 
4. Barzel US, et al. Excessive dietary protein can adversely affect bone. J Nutr 128:1051-1053, 1988
5. Sampath A, et al. Kidney stones and the ketogenic diet: risk factors and prevention. J Child Neurol. 2007 April:22(4):375-378
6. Poplawski MM, et al. Reversal of nephropathy by a ketogenic diet. PLoS One 6:1–9, 2011