By Stephen Byrnes, PhD, RNCP
Clinically, I have used low-carbohydrate, high fat and protein diets to very good effect, especially with those conditions that are worsened by excessive carbohydrate intake, e.g., diabetes, chronic fatigue, fibromyalgia, and heart disease. When properly practiced, low-carb diets are not harmful.
Some experts believe that excessive protein consumption, particularly animal protein, can result in heart disease, stroke, osteoporosis, cancer and kidney stones.
It is excessive carbohydrate intake, not protein or animal protein intake, that can result in heart disease and cancer (1).
Readers should note that the type of diet vegetarian expert advocate are high carbohydrate one because that is exactly what diets that are low in protein and fat are. Furthermore, the idea that animal products, specifically protein, cholesterol, and saturated fatty acids, somehow factor in causing atherosclerosis, stroke, and/or heart disease is a popular idea that is not supported by available data, including the field of lipid biochemistry (2).
The claim that animal protein intake causes calcium loss from the bones is another popular nutritional myth that has no backing in nutritional science. The studies that supposedly showed protein to cause calcium loss in the urine were NOT done with real, whole foods, but with isolated amino acids and fractionated protein powders (3).
When studies were done with people eating meat with its fat, NO calcium loss was detected in the urine, even over a long period of time (3). Other studies have confirmed that meat eating does not affect calcium balance (4) and that protein promotes stronger bones (5). Furthermore, the saturated fats that many experts believe are so evil are actually required for proper calcium deposition in the bones (6).
The reason why the amino acids and fat-free protein powders caused calcium loss while the meat/fat did not is because protein, calcium, and minerals, require the fat-soluble vitamins A and D for their assimilation and utilization by the body. When protein is consumed without these factors, it upsets the normal biochemistry of the body and mineral loss results (7). True vitamin A and full-complex vitamin D are only found in animal fats.
If the protein-causes-osteoporosis theory teaches us anything, it is to avoid fractionated foods (like soy protein isolate, something most vegetarians would no doubt encourage readers to consume) and isolated amino acids, and to eat meat with its fat.
New evidence shows that women who ate lots of meat had fewer hip fractures compared to those who avoided it (8) and that vegan diets place women at a greater risk for osteoporosis (9).
The claim that protein intake leads to kidney stones is another popular myth that is not supported by the facts. Although protein restricted diets are helpful for people who have kidney disease, eating meat does not cause kidney problems (10). Furthermore, the fat-soluble vitamins and saturated fatty acids found in animal foods are pivotal for properly functioning kidneys (11).
Many experts attempt to explain how meat supposedly "acidifies" the blood, leading to greater mineral loss in the urine is also incorrect. Theoretically, the sulfur and phosphorus in meat can form an acid when placed in water, but that does not mean that is what happens in the body.
Actually, meat provides complete proteins and vitamin D (if the fat or skin is eaten), both of which are needed to maintain proper acid-alkaline balance in the body. Furthermore, in a diet that includes enough magnesium and vitamin B6 and restricts simple sugars, one has little to fear from kidney stones (12).
Animal foods like beef, poultry, and lamb are good sources of both nutrients as any food and nutrient content table will show. It also goes without saying that high protein/fat and low-carbohydrate diets are devoid of sugar.
Some believe that the weight loss on high-protein diets is mostly from water loss is strange given that low-carb proponents like Robert Atkins, MD, tell their devotees to drink lots of water while on the diet. Initially, there is a water loss (as with any diet), but the high water intake afterwards would certainly offset any more drastic "water losses."
Others believe that weight loss occurs on high protein/fat diets because the person eats less food because he or she gets fuller faster on fat. Given that fat has more than twice as many calories than either protein or carbohydrate, this explanation is far from satisfactory.
In other words, you may not eat as many carbohydrates as you did before you went on the high protein diet, but because you're ingesting more fat, which has over twice as many calories as carbohydrate, your actual caloric intake is likely to stay the same or be higher than it was before.
Some claim that plant-based proteins like those found in soy, lower LDL cholesterol and raises HDL (good) cholesterol. This prevents the build up of arterial plaque which leads to atherosclerosis and heart disease, thus reducing the risk of heart attack and stroke.
This is yet another nutritional fantasy that although popular, is not true. The HDL/LDL theory has been thoroughly debunked by a number of prominent researchers (13) and LDL serves many useful functions in the body -- there is nothing "bad" about it (14).
Cholesterol is actually used by the body as an antioxidant (15); vegetarian diets do not protect against atherosclerosis or heart disease (16); and female vegans have higher rates of death from heart disease than female meat eaters (17).
Others contend that vegetable-protein diets enhance calcium retention in the body. This is simply wrong as "vegetable proteins" do not contain the fat-soluble vitamins A and D which are needed to assimilate calcium (and protein and other minerals). Furthermore, numerous plant compounds like oxalates and phytates inhibit calcium absorption.
Unfermented soy products, in particular, are noted for their high phytic acid content and phytates block mineral absorption (18).
Many experts advise us to replace vegetable protein for animal protein and unsaturated fats "like olive and canola oils" for saturated fats, is dubious at best and dangerous at worst. A number of recent and prior studies catalog the veritable witches brew of toxins found in processed soy products (19) and canola oil has caused vitamin E deficiencies in lab animals (20).
Canola oil is also quite susceptible to rancidity due to its high level of alpha-linolenic acid; in the deodorization process used with canola oil, harmful trans-fatty acids are created (21).
Lastly, studies have not born out the claims that vegetarians have lower cancer rates than the general population. A large study on vegetarian California 7th Day Adventists showed that, while the Adventists had slightly lower rates for some cancers, their rates of malignant melanoma; Hodgkin's disease; and uterine, prostate, endometrial, cervical, ovarian, and brain cancers were higher than the general population, some quite significantly. In the paper, the authors wrote that,
Meat consumption, however, was not associated with a higher cancer risk.
No significant association between breast cancer and a high consumption of animal fats or animal products in general was noted. (22)
Indeed, Dr. Emmanuel Cheraskin's survey of 1040 dentists and their wives showed that those with the fewest health problems as measured by the Cornell Medical Index had the MOST protein in their diets (23).
The facts are that high-protein diets, when consumed in balance with enough water, fat and fat-soluble vitamins, and nutritional factors from non-starchy vegetables, ARE healthy.
They are not guilty of the things many health experts blame on them. Minimally processed animal foods like beef and lamb are healthy foods that are rich in a number of nutrients that protect and enhance several body systems: taurine; carnitine; creatine; glutathione; vitamins A; D; several of the B-complex, including B6 and B12; minerals like chromium, magnesium, sulfur, iron, zinc, and phosphorus; complete proteins; and coenzyme Q10, needed for a healthy heart.
If readers want to get an accurate assessment of lower-carbohydrate diets, they should check out reliable books on the subject. (24)