Are Low Carbohydrate Diets Dangerous?
This is probably the biggest and most controversial myth in the health and fitness industry. You hear so many nutritionists and dietitians deride low carbohydrate diets as dangerous, especially in regards to damage to the kidneys and the heart. And if you have been around the industry long enough, you have probably heard that high protein/low carb diets can also cause osteoporsis and how dangerous ketosis is. So let us kick this myth square in teeth right now.
The danger to the kidneys while eating in a low carb/high protein fashion is perhaps the most often repeated myth in regards to low carb dieting. It comes from the medical fact that reducing protein intake will lessen the decline in kidney function in people who already have a kidney (renal) disease. Now because this works for patients with existing renal failure, people have decided that the opposite is also true – eating high amounts of protein will cause renal failure. But hold on just a second there hombre... A high protein intake does NOT cause this too happen in normally functioning kidneys and there is absolutely no medical evidence to suggest otherwise. In fact, a study in the American Journal of Kidney Disease showed the protein intake had no impact on GFR (which is a measure of renal function) in healthy male subjects1. Backing this up is the Nurses’ Health Study that reported high protein intake is not associated with kidney function decline in females with normal kidney function2.
Ding. Ding. Next round. The heart health issue.
This is exculsively related to the increased saturated fat intake while on a low carb diet and the effect it has on blood chlosterol. If you are not eating carbs, you have to be eating a bit more fat right? And we all know eating too much fat is bad and causes high chlosterol right? Well not necessarily. This is what we do know. Dietary fat will have an effect on blood chlosterol but whether that matters that much remains to be seen. For instance, 50% of heart attacks happen to people with completely normal chlosterol numbers3. Meanwhile, you have the Tokelauans whose diet should be causing them to drop dead left right and center from cardiac arrest with 63% of there diet coming from saturated fat. Now their average chlosterol levels are a bit high compared to western standards but their incidence of heart disease is virtually non-existent4. I am sure many other Pacific Island nations are all on the same boat here (no pun intended!).
But wait there is more.
Most of us know that cholesterol can be broken down into either high density lipoprotein (HDL), which is the protective version; or low density lipoprotein (LDL), which is the bad guy. What most people do not know is that HDL and LDL also have different subclasses in the body and these subclasses behave quite differently. The main thing we have to be aware of is that LDL has at least two types of subclasses. Plasma apolipoprotein A (apo A) are a large fluffy type molecule while apolipoprotein B (apo B) are small dense molecules. Apo B are the suckers that cause plaque and stop the ticker from working while pattern A is a lot less harmful. And guess what? High protein diets decrease apo B and also increase the protective HDL cholesterol compared to a traditional high carbohydrate/low fat diets5. The high carbohydrate diet also increases triglycerides5, which has been shown in almost all major studies comparing high carb to low carb diets. Low HDL and high triglycerides (which is the opposite result of low carb dieting) is the best predictor of heart disease and a lot more lethal than an overall cholesterol number6.
The last real issue here is that the major research we have linking saturated fat to heart disease does not distinguish between saturated fat and trans-saturated fat7. This is a real problem because trans-saturated fat in the diet is a definite ‘no no’ as it raises lipoprotein(a), which is a risk factor in heart disease, lowers HDL cholesterol and also raises the bad LDL cholesterol. It is a bit like being guilty by association – by not differentiating between the two types of fat, it is very likely that saturated fat was the innocent bystander. Forward thinking physicians and researchers, like Jonny Bowden PhD, actually believe the bad rap saturated fat has got over the years has actually almost exculsively stemmed from trans-saturated fat. New research is also showing that when enough fiber is included in a diet along with omega 3 fats, this almost eliminates the association between saturated fat and heart disease8.
Round 3.
The osteoporosis scare with low carb/high protein diets come from the fact that higher levels of protein in the diet results in higher levels of calcium in the urine. From here, physicians and others have concluded that protein causes bone loss. Fortunately for those females (and the odd male) at risk of osteoporosis but wanting to get lean, there have been a number of recent studies to prove otherwise. The fact that there is more calcium excretion with a high protein diet does not actually matter. We just need to make sure we are holding on to more than what we are losing. And that is exactly what happens. High protein diets result in significantly more calcium absorption than a diet containing a similar amount of protein to what most national dietary associations recommends9! Backing this research up is the Framingham Osteoporosis Study, which was run over a four year period in both males and females with an average age of 75. They found that those who consumed more protein had less bone loss10. They also found that lower protein intakes resulted in greater bone less especially at the femur and spine. You should also know this (especially if you are at risk of osetoporsis) – extra calcium intake; whether it be through supplements, diary or whatever; will NOT positively affect the skeleton with a low protein intake11. Morale of the story – protein intake will actually decrease, not increase, osteoporosis risk.
Last round.
The Ketosis issue. If you have low carb dieted before, you have almost certainly heard about this. Ketosis is a metabolic state where after eating very little carbohydrate, you produce ‘ketones’ for energy and your body almost solely burns fat for fuel. Trust me on this – the metabolic state of ketosis is quite benign. Ketones are simply products of a normal metabolism that means (as I have mentioned) you are breaking down fat for energy. Now it is time for a few definitions. The normal level of ketones in the body is 0.1 mmol/dl and mild ketosis is classed as 0.2 mmol/dl12. Consider that after strenuous exercise your blood ketone body concentration can be up to 2 mmol/dl and if you were to believe the soothsayers, then any type of exercise would be dangerous in terms of ketone concentrations. The problem is that the medical & dietetic community has confused ketosis with another condition –diabetic ketoacidosis13. Diabetic ketoacidosis can only occur in type I Diabetics (where the patient cannot make insulin) and is indeed life threatening. The problem is that because there is no insulin to stop the effect of glucagon (the hormone responsible for breakdown of fat), ketones accumulate very sharply in the body. Also with no insulin to lower blood glucose levels, the ketones cannot be used for fuel as in a normal non type I diabetic patient. This is because glucose is the preferred fuel for the body. So the ketones keep accumulating until they reach toxic levels - but only in type 1 diabetics. Just to reinforce this, compare the ketone production in g/day on a true almost nil carbohydrate ketogenic diet which is 115-180g/day to diabetic ketoacidosis which is 400g/day12. It just does not add up. To further this point, ketogenic diets have been used to treat epilepsy for over 70 years in major health institutions and there have never been any reported serious patient complications13.
Knockout.
Remember low carbohydrate diets should be avoided or modified if you fit in following three catergories - type 1 diabetic, a nursing/pregnant woman or have an existing kidney disease. If you do not fit in the above, ketosis and low carb dieting is perfectly safe and (more than likely) beneficial for you.
References
1. T.B. Wiegmann et al., “ Controlled Changes in Chronic Dietary Protein Intake do Not Change Glomerular Filtration Rate,” American Journal of Kidney Diseases 15, no. 2 (February 1990): 147-54
2. E.L. Knight et al., “ The Impact of Protein Intake on Renal Function Decline in Women with Normal Renal Function or Mild Renal Insufficiency,” Annals of Internal Medicine 138 (2003): 460-67
3. E. Braunwald, “Shattuck Lecture- Cardiovascular Medicine at the Turn of the Millennium: Triumphs, Concerns, and Opportunities,” New England Journal of Medicine 337, no. 19 (1997): 1360-69
4. I.A Prior et al., “ Cholesterol, Coconuts, and Diet on Polynesian Atolls: A Natural Experiment,” American Journal of Clinical Nutrition 34, no. 8 (August 1981): 1552-61
5. J.D. Furtado et. al., "Effect of Protein, Unsaturated Fat, and Carbohydrate Intakes on Plasma Apolipoprotein B and VLDL and LDL Containing Apolipoprotein C-III: Results from the OmniHeart Trial", American Journal of Clinical Nutrition 87 (6), June 2008: 1623-30
6. J. Michael Gaziano, “Fasting Triglycerides, High Density Lipoproteins and Risk of Myocardial Infraction,” Circulation 96 (1997): 220-25
7. A. Ascherio and Walter Willett, “Health Effects of Trans Fatty Acids,” American Journal of Clinical Nutrition 66, suppl. 4 (October 1997): 1006s-1010s
8. A. Ascherio et al., “Dietary Fat and Risk of Coronary Heart Disease in Men: Cohort Follow Up Study in the United States," British Medical Journal 313 (13 July 1996): 84-90
9. J.E. Kerstetter et al., “Dietary Protein Affects Calcium Absorption," American Journal of Clinical Nutrition 68 (1998): 859-65
10. M.T. Hannan et al., “Effect of Dietary Protein on Bone Loss in Elderly Men and Women: The Framingham Osteoporosis Study,” Journal of Bone and Mineral Research 15, no. 12 (December 200): 2504-12
11. R.P. Heaney, “Editorial: Protein and Calcium- Antagonists or Synergists?” American Journal of Clinical Nutrition 75, no. 4 (2002): 609-10
12. McDonald, L., “The Ketogenic Diet: A Complete Guide for the Diet and Practitioner”, Morris Publishing: Kearney, NEB. (1998)
13. Bowden, J., “Living the Low Carb Life: Controlled Carbohydrate Eating fro Long Term Weight Loss”, Sterling Publishing: New York, NY (2004)