The side effects
Many of the side effects of low carbohydrate diets were already known in the 20th century when the classic ketogenic was devised by Dr. Russel Wilder to treat children with epilepsy that could not be treated with medication. The short-term side effects reported were diarrhoea, constipation and vomiting. Long term side effects reported include vitamin deficiencies, kidney stones, restricted growth, fatal cardiac arrhythmias, pancreatitis, high cholesterol, and bone fractures.
It is also known that ketones seem to cause neurological problems for the developing foetus in pregnant women. With babies born from mothers who have been on a ketogenic diet losing on average 10 IQ points (13,14).
The ketone bodies the body produces for energy when the glycogen reserves are depleted are acidic. In extreme cases this can lead to ketoacidosis, a life-threatening condition. The body neutralises this acid with phosphate found in the bones. Bones are mainly composed of calcium phosphate; the phosphate reacts with the acid and the calcium is excreted in the urine by the kidneys. This leads to increased bone demineralisation, which is a cause for the increased risk for bone fractures and osteoporosis. As low-carbohydrate diets tend to be deficient in calcium as well, there is a significant loss of bone health for people on low carbohydrate diets.
The excess calcium in the urine can be a cause for the formation of kidney stones. Especially because when on a low carbohydrate diet the urine has an abnormally low concentration of citrate, which normally helps dissolve the free calcium. And the lower pH of the urine stops uric acid from dissolving, which leads to the formation of crystals that can initiate calcium stone formation.
There are also studies that suggest that a low carbohydrate or ketogenic diet could be beneficial for people suffering from Alzheimer’s disease, a chronic neurodegenerative disease which impairs cognitive function and usually worsens over time. The exact cause of Alzheimer’s is poorly understood but it’s widely accepted that to help prevent or slow its progression we need to focus on the heart and vascular health of the body. This makes sense as the brain, which accounts for 2% of the body weight and uses 25% of the body’s energy, is much more susceptible to vascular and inflammatory risk factors.
As we age, it becomes harder for glucose to cross the blood brain barrier to provide the brain with its preferred fuel source. When you adopt a low carbohydrate or ketogenic diet, the ketone bodies that are formed can provide your brain with extra fuel, to make up for any deficit. This explains the benefits seen in the studies on this subject, which are mostly studies over relatively small time periods. However, by adopting this kind of diet, you do provide your brain with an alternate source of energy which could have a beneficial effect on the progression of Alzheimer’s disease, but by doing so your diet will provide you with much less nutrients that are beneficial for your overall vascular health.
Ketogenic diets often lead to problems with the glucose and lipid regulation in your body. This causes harmful by-products to be created and leads to the deposition of amyloid and tau proteins, which are both strongly associated with Alzheimer’s disease. Thus, the beneficial effects of adopting a ketogenic diet for the treatment of Alzheimer’s are short-lived and could have long term harmful effects.
Another issue with low carbohydrate diets is the effect they have of our gut microbiome. Diets high in fat have an adverse effect on the microbiome, several beneficial bacteria decrease in numbers, and are being replaced with unfavourable bacteria species (15,16). These changes become more pronounced on the long term, with possible negative health effects. The good bacteria in our gut feed on the fibre from whole grains, legumes, fruits, and vegetables, which are all restricted on low carbohydrate diets. When the good bacteria diminish the pH level of the colon rises, which creates a more favourable environment for the pathogenic bacteria. Normally, the beneficial bacteria create an acidic environment in the gut which is hostile to the bad bacteria. It even appears that these pathogenic bacteria influence your brain through the vagus nerve, which connects the gut with the brain, and make you crave more high fat foods. Thus, low carbohydrate diets create a cascade of effects which all negatively influence the health of your gut microbiome.
