Do dietitians in Canada prescribe carbohydrate restriction? A survey of knowledge, use and barriers

Before 2020, diabetes nutrition care excluded carbohydrate restriction but growing evidence supports this approach now included in Canada’s Clinical Practice Guidelines. We assessed the knowledge, use and barriers of dietitians to improve diabetes nutrition care in Canada.

In Spring 2020, Diabetes Canada updated the Clinical Practice Guidelines to include carbohydrate restricted-diets as a therapeutic option for patients living with type 2 diabetes and/or metabolic syndrome. Prior to this, however, dietitians practised diabetes nutrition care without formal education or guidance on protocol for dietary approaches involving little or no carbohydrates. This is a significant gap in nutrition care for patients living with metabolic conditions and has implications for patient safety.

Dietary patterns are a major contributor to chronic disease, including obesity and type 2 diabetes. An evidence base exists to support the therapeutic use of carbohydrate restricted-diets in chronic illnesses other than epilepsy (its first discovery), as multiple experimental and animal studies show this approach can improve glycemic control and weight loss. Yet, no research to date exists on the current prescription practice of this type of dietary approach among Registered Dietitians (RDs) in Canada which makes the process of prescribing carbohydrate-restricted diets more difficult. Thus, our goal was to understand the knowledge base, the use of and the barriers to RDs to address gaps in both patient care and professional nutrition education.

We used an online cross-sectional survey (January-December 2020) to determine the extent to which RDs in Canada prescribed carbohydrate-restricted diets, and to describe what factors might differ between RDs who do and do not. We received approximately 300 responses in both French and English, with an eligible sample of 274 for our analysis. We found a statistically significant difference between RDs who reported they prescribed carbohydrate-restricted diets or not in the following factors:

  • reported knowledge level (p<0.001)
  • literature review (p<0.05)
  • clinician referrals/medical support (p<0.001)
  • personal experience with this dietary approach (p<0.001)
  • patient-initiated referrals for this dietary approach (p<0.01).

 In our sample, over two-thirds of respondents (67%) reported having zero or basic level of knowledge in therapeutic use of carbohydrate restriction, and one quarter (25%) had not reviewed scientific literature regarding this dietary approach. Notably, RDs who had read the literature typically used peer-reviewed studies or professional groups but online communities of interest were also common sources of information.

There were many different barriers reported by dietitians to prescribing carbohydrate-restricted diets (Figure 1). Patient-related or other reasons (e.g. beliefs) and lack of knowledge were the more prevalent barriers among dietitians with limited or no experience, while lack of support/clinician referral was the most prevalent barrier among dietitians who regularly prescribed carbohydrate-restricted diets in their practice.


Figure 1. Frequency of reported barriers to prescribing carbohydrate-restricted diets across levels of prescribing in our sample of dietitians.

Figure 2 shows the results of our multivariable regression models. We found that RDs were more likely to prescribe carbohydrate-restricted diets when they had intermediate/expert knowledge (nearly 6 times), a clinician’s referral (over 3 times) and personal experience, whether a former user (over 2 times) or a current user of TCR (over 9 times), compared to no knowledge, no referral, or no experience. No associations were found for geography, years of professional practice or patient psychological conditions (e.g. eating disorders).


Figure 2. Dietitians’ practice characteristics associated with the odds of prescribing carbohydrate-restricted diets: Level of knowledge (top left); clinician referral (top right); personal experience (bottom left)

We had some unexpected findings that over 10 or 20 years of practice did not influence whether or not a dietitian used this dietary approach for their patients. We wonder if the underlying factor could be the level of knowledge and research into this dietary approach. Without understanding the background, physiological changes, and safety profiles of a dietary approach (regardless of dietetic experience and/or possibly because of their experience), it would make sense that an RD would not prescribe that dietary approach.

Similarly, we found no association for the type of health condition, specifically eating disorders or other psychological-related conditions that would be contraindicated with nutrition therapy using a restrictive diet. Possible reasons for this might be:

  1. RDs prescribe diets as tools based on the individual patient's needs rather than from a dogmatic approach
  2. low sample size for the number of RDs who treat eating disorder

More research is needed to better understand this.

Many of our findings were as expected and supported our hypothesis of dietitian differences between carbohydrate-restriction prescribers and non-prescribers. In some cases, the magnitude of associations was very larger and results indicated the relative contributions of three major modifiable factors that could improve RDs prescribing of carbohydrate-restricted diets to their patients:

  1. personal experience: when a person tries a diet for themselves, they might develop a nuanced understanding of the diet and confidence around discussing/prescribing the diet which results in better patient monitoring.
  2. intermediate-to-expert knowledge: it makes sense that a person who has studied the literature around safety, efficacy, physiological changes and monitoring requirements for a new dietary approach will be confident prescribing it for the right patient. The opposite is also true: it would make sense to avoid prescribing a diet that one is not familiar with.
  3. clinician referral/medical support: given the significant risk around proper medication management on TCR, if RDs are not working with a physician, then the Hippocratic Oath dictates they should not prescribe this diet to patients who are on specific medications. Thus, it would make sense that a RD with a clinician referral is more likely to prescribe a diet requiring medication monitoring by that referring medical team.

This research published in Nature’s European Journal of Clinical Nutrition adds to this burgeoning nutrition and diabetes care literatures on this topic. It highlights the need for new educational tools and resources on scientific evidence for therapeutic use of carbohydrate restriction among RDs as well as other health professionals. Better patient nutrition care requires a strengthening and expansion of multidisciplinary teams, so as to better support RDs in Canada to safely implement TCR in appropriate patients with chronic illness, especially metabolic conditions such as type 2 diabetes.

This research may also provide a better understanding around RD prescribing and barriers to other new, evidence-based dietary approaches.

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