Pros & cons of low carb diet

    “Low carb diet” is chosen by people for tackling various problems such as overweight, obesity, diabetes ,PCOS or polycystic ovarian syndrome, and for preventing cardiovascular diseases, type 2 diabetes and cancer.

What is low carb diet?

Consuming less than 26% of daily energy from carbohydrates, comparing with the" healthy eating guidelines" which recommends that about 50% of daily energy may come from carbohydrates , is called  “low carb  diet”

In this diet carbohydrate consumption is reduced very much. To achieve the low carb level some foods are avoided or limited .These restricted foods include:

Sugary foods and drinks

Grains -cereals, bread, pasta, rice, etc.

Legumes -beans, peas and lentils

Tubers-potatoes, sweet potatoes and butternut squash

 fruits - bananas, mango and pineapple

Alcohol

Fruit juice .

   Following a very low carbohydrate diet makes some changes in the metabolism. It creates a ketosis like state in the body. Ketosis is a metabolic state which occurs when a very low-carb is consumed[only 5-10% of energy from carbohydrates).The body cells are forced to break down fat for energy as carbs are not available; and ketone bodies or ketones are formed, and this is why it is called ketosis or ketogenesis. So low carbohydrate diet mimics “the fasting state” forming ketones.

Keto diet and diabetic ketosis, low carb diet - How do they differ?

Keto diets restrict carbohydrates to induce nutritional ketosis [ as described above] and typically limit carbs to 20 to 50 grams daily. Restricting carbs to under 50 gms induces glycogen [stored sugar] depletion and ketone production from the mobilization of fat stored in adipose tissue.

Nutritional ketosis produces ketone bodies (acetoacetate, acetone, and beta-hydroxybutyrate) and is measurable as serum or urinary ketones.

 Nutritional ketosis generally increases serum ketones from 1 mmol/L to 7 mmol/L but does not produce metabolic acidosis.

Diabetic ketoacidosis, by definition, includes metabolic acidosis, hyperglycemia[ high blood sugar level], and serum ketones (generally over 20 mmol/L).Here metabolic acidosis happens. Metabolic acidosis is a state associated with excess of hydrogen ions.

Low carb diet ketosis- there is no evidence that very low-carb intake produces metabolic ketoacidosis and remains safe in patients, even with type 2 diabetes[2].

Better short term control of blood sugar in type 2 diabetes has been achieved with a low-carb diet, but  no evidences confirm regarding its benefits in long term .

Do low carb diet increase cardiovascular disease risk causing heart attacks and stroke?

    Low-carb diets which are high in plant-based protein and plant-based fats have been shown to be associated with decreased mortality from cardiovascular diseases such as heart attack, stroke etc. It does not increase the risk for heart attacks and stroke.

However, Low-carb diets if compensated by foods high in saturated fat, which can lead to an increase in Low-Density Lipoprotein (LDL), known commonly as the bad cholesterol .For example, if a person is taking only low carb diet but he eats red meat and fried food  this may increase the bad cholesterols. This type of unhealthy choices with low carb diet can increase the risk of fatty liver and heart diseases.

   People who were on low carb diet along with plant-based fat and protein, had lower mortality and occurrence of cardiovascular diseases. While those people who consumed animal-based fat and protein had a higher risk of mortality and cardiovascular risk.

Adverse effects of low carb diet

    Following a very low-carbohydrate diet, may cause symptoms such as diarrhoea, tiredness, cramps and headaches. The brain mostly uses sugars from healthy carbohydrates, and deficiency of sugar may lead to confusion and irritability.

    Fruits and vegetables contain natural sugars, but they also contain fiber, vitamins, minerals and antioxidants in the form of polyphenols. Therefore limited intake of fruits and vegetables for reducing carbs may affect nutrition of the whole body adversely. Lowering of fiber in the diet may cause constipation and it has impact on the gut microbiota or microorganisms which live in the gut which protects against harmful microbes. Impact on gut microbiota may enhance the risk of bowel cancer.

However, some studies have shown an increased mortality risk with a carbohydrate intake of less than 40%. [4].

Another study found that a healthy low-carb diet and low-fat diets were associated with lower mortality , and unhealthy low-carb and low-fat diets were associated with higher mortality [5]. 

There is widespread belief that high protein, low carb diet may cause kidney damage. But there are no data to associate high protein load with worsening kidney function in those with normal kidneys[6].

But in people already having serious kidney diseases are not advised to take high protein diet.

Benefits of low carb diet 

Does low card diet help to prevent diabetes?

Carbohydrate intake is associated with a spike in blood sugar levels. When you eat food rich in carbs or sugar blood sugar level increases.

Dietary carbohydrates increase insulin needs. When blood sugar levels are high insulin production also increased by body. In non diabetics it helps to remove blood sugar and cells take up glucose. But in people with diabetes both blood sugar and blood insulin levels remain high as insulin will not take up glucose and this state is called insulin resistance. Insulin resistance begins in the prediabetic stage and continues.

Studies show that reduction of carbohydrate intake can improve glycemic control or sugar managing potential of body [7].Therefore low carb diet helps to control blood sugar in people having diabetes or prediabetes.

It is a very commonly observed fact that people who wants to lose weight often reduce intake of  added sugars, rice , juices etc.

There is some evidence that a low-carbohydrate diet may help people lose weight more quickly than a low-fat diet (8,9].That means reducing carbs may help you lose some weight. Low carb diet may also help them maintain that weight loss.

References

1.    https://www.ncbi.nlm.nih.gov/books/NBK537084/

2.    https://pubmed.ncbi.nlm.nih.gov/23801097/

3.    https://dieteticallyspeaking.com/the-pros-and-cons-of-low-carb-diets/

4.    https://pubmed.ncbi.nlm.nih.gov/23372809/

5.    https://pubmed.ncbi.nlm.nih.gov/31961383/

6.    https://pubmed.ncbi.nlm.nih.gov/16174292/

7.    https://pubmed.ncbi.nlm.nih.gov/25287761/

8.    https://www.hsph.harvard.edu/nutritionsource/carbohydrates/low-carbohydrate-diets/

9.    Foster GD, Wyatt HR, Hill JO, et al. A randomized trial of a low-carbohydrate diet for obesity. N Engl J Med. 2003;348:2082-90.