Low Carb EffectsOn this page go to:
- Key points of low-carb current research results
- Vitamin and mineral deficiencies, with increased risk of cancer and heart disease
- Serious side effects
© Contact Human Health and Animal Ethics
Key points of low-carb current research results
Low-carb diets depart drastically from the dietary intakes recommended by the most important medical and nutrition authorities, including the U.S. Department of Agriculture and the National Institutes of Health.
Until not long ago there had been few significant long-term scientific studies on low carb diets and the Atkins Diet. There have been more studies in recent years, but their duration, with few exceptions, is not long enough to establish the effect of the diet on the risk of heart disease and cancer, or on bone health, renal function and cardiovascular function, which requires a long-term period of observation.
There is controversy over the results of much of this research, but nevertheless there is some picture emerging.
Details of the research carried out are described below but, if you wish to skip them, here we're giving a summary of the results' two key points.
1. Perhaps the most important result comes from a 20-year old study, and regards what kind of protein is best for health.
Many low carb diets, like the Atkins, although they are not all the same, tend to contain high amounts of protein. Since it's usually been assumed that this high protein would be of animal origin, this has raised concern about the long-term effects of a large consumption of meat and animal fat particularly on the health of the heart. It has now been found that a high-protein low-carb diet in which the sources of protein are vegetable and not animal, thus replacing meat and eggs with pulses, soya, tofu, nuts, quorn and the like, is actually beneficial to the heart.
2. Another seemingly clear message from the research findings is that ketogenic diets, i.e. diets in which the amount of carbohydrates is minimal, as in the first stage (induction) of Atkins, can lead to a rapid weight loss, compared with other diets, but this weight loss is not maintained. So, whatever the metabolic advantage, i.e. the greater weight loss with the same number of calories, that very low-carb diets may have over alternative diets is lost generally within a year, when weight returns at the pre-diet level or sometimes even higher. In this all fast diets, unfortunately, seem to equal each other.
Vitamin and mineral deficiencies, with increased risk of cancer and heart disease
A 10-year study on elderly Swedish men published in 2010 in The American Journal of Clinical Nutrition compared the mortality rates of groups of subjects on a diet following the World Health Organization dietary guidelines, a Mediterranean diet, and a carbohydrate-restricted diet, which anyway was allowing 40% carbohydrates, much more than the Atkins recommended 4%. The study concluded:
Adherence to a Mediterranean-like dietary pattern reduced mortality, whereas adherence to a CR [carbohydrate-restricted] dietary pattern appeared to increase mortality.
One of the most extensive and interesting studies published on low-carbs diets is the Nurses' Health Study, a survey of 82,802 women which began in 1976, with 20 years of follow-up, and was published in the NEJM in 2006. The study found that low-carbs, high-protein, high-fat diets do not increase the risk of coronary heart disease in women but on the contrary reduce it, but only when the sources of fat and protein are vegetable and not animal. So low-carb is OK for the heart, but only if the protein comes from vegetable, not animal, sources. This finding confirms the current "received wisdom" on the matter. This is a key finding and comes from probably the longest study ever carried out.
Some studies consider low-carb diets and/or Mediterranean diets as possible alternative to low-fat diets, which are the usually recommended; these studies are however short-term and do not follow up the subjects after 2 years. One published in the New England Journal of Medicine (NEJM) concludes:
Our results suggest that health care professionals might consider more than one dietary approach, according to individual preferences and metabolic needs, as long as the effort is sustained. [Emphasis added]
A study in The American Journal of Clinical Nutrition has found that ketogenic low-carb diets like Atkins, more extreme in their carbohydrate restriction, compare unfavourably with nonketogenic low-carb diets, in that they both reduced body weight and insulin resistance, but the more carb restrictive diets were associated with several adverse effects. The use of ketogenic diets for weight loss was not recommended.
The problem is that the results of each individual study, especially if the sample studied was not large or was not representative of the general dieting population, are not enough to draw a conclusion. That's why systematic reviews, that collect results of a large number of studies on the same topic, are a better approach.
In 2003 a systematic review in the highly-regarded Journal of the American Medical Association reached this verdict:
"Conclusions: There is insufficient evidence to make recommendations for or against the use of low-carbohydrate diets, particularly among participants older than age 50 years, for use longer than 90 days, or for diets of 20 g/d or less of carbohydrates. Among the published studies, participant weight loss while using low-carbohydrate diets was principally associated with decreased caloric intake and increased diet duration but not with reduced carbohydrate content." [Emphasis added]
In 2004 the British Lancet, one of the world's most prestigious medical journals, carried out its own review of Atkins Diet. It concluded:
Long-term studies are needed to measure changes in nutritional status and body composition during the low-carbohydrate diet, and to assess fasting and postprandial cardiovascular risk factors and adverse effects. Without that information, low-carbohydrate diets cannot be recommended. [Emphasis added]
The Atkins Diet is the direct opposite of the food pyramid recommended by the American Cancer Society, the National Institutes of Health, the American Academy of Pediatrics, and the American Dietetics Association. It also lacks most of the foods naturally containing important nutrients like vitamins and minerals, resulting in vitamin and mineral deficiencies, and is high in fat.
The Atkins diet and similar ones that promote a high intake of animal protein are also being blamed by medical authorities for putting dieters at risk of developing a host of life-threatening conditions, including heart disease and stroke.
The Journal of the American Medical Association, the leading American medical publication, published the results of a 20-year study of over 148,000 adults between the ages of 50 and 74: it found that those who had the highest consumption of red meats were 50 percent more likely to contract cancer in the lower colon than those who least consumed them. This is consistent with a Harvard research showing that Atkins-type diets are linked to a three-fold increased risk of colon cancer.
Eating a lot of processed meats, e.g. pastrami, bacon, ham and salami, and red meat for a prolonged period of time poses a colon cancer risk.
These are numbers and percentages that could be relevant to the Atkins dieters, who are encouraged to consume meat, said head of epidemiological research at the American Cancer Society Dr. Michael J. Thun, who added:
"The Atkins diet became popular just recently, so no one knows the health effects long-term. But the accumulating evidence that a diet high in red meat or processed meat increases the risk of colon cancer indicates that it would certainly be undesirable to remain on the Atkins diet long-term." [Emphasis added]
Another result comes from the magazine of Oxford University students:
"A group of Oxford scientists have subjected themselves to the controversial Atkins diet, with a number suffering ill health as a result.
"The researchers found that the diet caused them to experience a fast and irregular heartbeat - a condition that can lead to heart failure in the long term.
"In the most extreme cases, it took participants two months to overcome the effects.
"The group of 17 researchers from the Physiology and Cardiology departments spent two weeks observing the effects of the diet, in which participants avoid carbohydrates in favour of protein rich foods such as meat, eggs and cheese.
"Dr Sheuermann-Freestone, who was leading the research, stressed the provisional nature of the findings, but commented that she would 'most certainly not' recommend anyone to follow the Atkins diet, despite the fact that participants did lose between two kilograms and five kilograms during the experiment.
"'The weight will be lost in a most unhealthy way with lots of possible side and long-term effects. It is much better to cut down a little on the carbohydrates, a lot on the fats, and exercise in parallel.'
"The study was conducted in conjunction with the British Heart Foundation in the hope of better understanding how free-fatty acids, which surround the heart, actually function.
"It is hoped that the results can be used in developing new treatments for diabetes and heart conditions.
"Despite widespread criticsm, 'Dr Atkins' New Diet Revolution', made famous by its large celebrity following, has now sold over six million copies, becoming one of the most popular fad diets of all time."
A study published in the American Journal of Kidney Diseases shows that high-protein, low-carb diets cause rapid and conspicuous loss of calcium in the urine, possibly leading to osteoporosis; studies of vegetarian diets, on the other hand, have shown effective and safe weight loss. Studies published in the Journal of the American Medical Association show that a vegetarian low-fat diet can reverse heart disease.
Serious side effects
Dr Atkins claims that his diet causes no adverse, negative side effects. Many health authorities and medical professionals disagree.
In a report on ketogenic diets, of which the Atkins Diet is an example, registered dietician and author Ellen Coleman says the Atkins Diet may have several serious side effects, among which ketosis, a potentially serious condition characterized by high levels of chemicals called ketones in the blood, often caused by a diet not providing enough carbohydrates, the main food group that produces energy and is a key part of a healthy diet.
Other serious side effects of the Atkins Diet are kidney problems, dehydration, calcium depletion, nausea, electrolyte loss, weakness.
Diabetics taking insulin risk becoming hypoglycemic if they do not have sufficient carbohydrates in their diets. And people exercising regularly may suffer from muscle fatigue and low energy levels because of reduced carbohydrate intake.
Research performed at the University of Texas found that Atkins-type diets also increase the risk for kidney stones.
Interestingly, even studies supporting the Atkins Diet found side effects like significantly higher cholesterol levels in some individuals and increased calcium excretion, potentially causing osteoporosis.
Registered dietician and spokeswoman for the American Dietetic Association Katherine Tallmedge said that an unpublished study funded by Atkins himself found that in the study the people who were on Atkins diet experienced everything from constipation to headaches to hair loss to bad breath.