Low carbohydrate, high fat diets for diabetes have recently re-emerged and have caught the attention of some members of the scientific community and the public.
What are the goals of diabetes care?
When you have diabetes, the aim is to manage your blood glucose levels, your blood fats and blood pressure as best as possible. Advice about food and eating is very important because in both short term (3-6 months), and the long term (2 or more years), it influences your health and how you feel. Advice should always be supported by the best quality science and be individualised for each person to match their health goals, personal and cultural preferences, their access to healthy choices, and their readiness and willingness to change. To this end, there is no single optimal diet for all people who have diabetes – there are many different ways of eating well.
What is a low carbohydrate diet?
Well, that’s part of the problem…’low carbohydrate’ is poorly defined.
In research, some have used ‘Very Low Carbohydrate Ketogenic Diets’ (VLCKD) with amounts from 20-50g carbohydrate per day (less than 4 ‘portions’). These diets often omit whole food groups and make it impossible to meet all known nutrient and fibre targets, and therefore could not be recommended for diabetes management in the long term.
Others have suggested that ‘Low’ is <130g/day (26% of energy based on a person’s intake of 8,400kJ/day). ‘Moderate’ carbohydrate falls between 130-230g/day (26-45% of energy based on a person’s intake of 8,400kJ/day) and then ‘High’ carbohydrate is >230g/day (45% of energy based on a person’s intake of 8,400kJ/day).
Important information about carbohydrate foods
The amount , type and frequency of carbohydrate foods in a diet pattern is an important consideration in the management of diabetes. Foods that are considered carbohydrate choices are many and varied, and are of differing quality. Low Glycaemic Index food choices (GI<55) are important in selecting the right carbohydrate foods for you. And overall the reduction in total energy (kilojoule) intake is key to glycaemic control in most people with Type 2 diabetes. Dietitians recommend people with diabetes spread their carbohydrate food choices over the day, to assist with glycaemic control.
According to Diabetes Australia, very low carbohydrate diets are not recommended for people with diabetes. The organisation states: ‘If you eat regular meals and spread your carbohydrate foods evenly throughout the day, you will help maintain your energy levels without causing large rises in your blood glucose levels. Diabetes Australia recommends people with diabetes eat moderate amounts of carbohydrate and include high-fibre foods that have a low glycaemic index.
Are carbohydrate foods needed by the body?
While there are specific requirements for amino acids (from proteins) in the diet, and essential fatty acids (from fats), there is talk that there is no specific requirement for carbohydrate.
This is not true. Both your brain and red blood cells require glucose and while some can be supplied by breaking down proteins in your body, there are a number of reasons why this is not beneficial and is specifically not recommended – for example, during childhood (due to growth requirements) and during pregnancy. The long term effect of placing this demand on the body has also not been tested and there is evidence to suggest that performance in mental and physical tasks could be affected. Therefore, a diet that is very low in carbohydrate may not be physically or mentally sustainable as a diet pattern.
In addition carbohydrate foods supply many nutrients. These include B vitamins and fibre from grains, and vitamins, minerals, dietary fibre and other plant components such as antioxidants from fruit and starchy vegetables. So without careful planning, it can be more difficult to meet nutrition needs on a low carbohydrate diet.
Consistent evidence indicates that in general, dietary patterns higher in plant-based foods such as vegetables, fruits, wholegrains, legumes, nuts and seeds, and lower in animal-based foods are more beneficial for overall health.
A word on saturated fats
In ‘Low Carb, High Fat’ (LCHF)diets, a variety of fats have also been suggested as replacements for carbohydrate foods. Some LCHF diets promote foods like coconut oil and animal fats (such as lard and butter), often suggesting these are more ‘natural’ sources of fat. The Dietitians Association of Australia believe this is misleading.
All fats are rich in energy (kilojoules) – containing twice the amount of kilojoules as either protein or carbohydrate – so if eaten in large amounts, can make weight control more difficult. The Australian Dietary Guidelines recommend Australians limit intake of foods high in saturated fat.
Foods high in saturated fat include:
- Many biscuits, cakes, pastries, pies, processed meats, commercial burgers, pizza, fried foods, potato chips, crisps and other savoury snacks.
- Butter, cream, cooking margarine, coconut and palm oil.
The final word
A Low Carbohydrate, High Fat diet may be used by some nutrition professionals in the short term to achieve particular health goals, but the effectiveness and safety of the diet has not been examined in the longer term. An argument for the use of the diet can potentially be supported by ‘established principles in biochemistry and physiology’, however long-term randomised controlled trials with consistent dietary methodology are lacking.
Therefore, this diet type remains controversial – and the Dietitians Association of Australia believes more research is required on the safety and efficacy of such a diet, in people with diabetes and the general population. What we do know from the evidence is that eating a wide variety of nutritious foods, in the right amounts, is crucial to optimal health. The Dietitians Association of Australia recommends people with diabetes seek advice from a health professional before dramatically changing their diet.
Source: Dietitians Association of Australia