Should vitamins be prescribed with weight management medication?

With highly efficacious weight management medications becoming available in the last few years, we are seeing many people enjoying substantial weight loss and improvement in health with these treatments. With the significant reduction in appetite and food intake that these medications can induce, as well as changes in food preferences for some people, it is important to consider whether a person is getting adequate nutritional and nutrient intake with treatment.

Previously, I have blogged about the importance of ensuring adequate protein intake.

Today, I ask the question: Should we be routinely recommending vitamins with weight loss medication?

An interesting review article provides a beautiful overview of nutritional considerations with weight loss medications.

Obesity, before treatment with medication, is associated with a higher risk of micronutrient deficiencies such as vitamin D, vitamin B12, folate, thiamine, iron, and zinc. Inadequate intakes of calcium, magnesium, and vitamins A, E, and C have also been reported in people with elevated weight. The risk of nutrient deficiencies in people with elevated weight can be reduced with a complete multivitamin.

Before starting treatment with weight management medication, authors recommend:

assessing risk factors for nutrient deficiency such as older age, history of gastrointestinal tract surgery, other chronic health conditions, eating disorders, monotonous diets, poor dietary choices, or food insecurity
evaluating nutrient intake before starting treatment
physical examination looking for any evidence of signs of nutrient deficiency
treating any pre-existing nutrient deficiencies
counseling on optimizing nutrient intake with dietary measures

Along with writing the prescription for weight management medication, they advise considering supplementation with vitamin D, calcium, and a complete multivitamin.

The review includes a beautiful table (Table 2, it’s a free download!) of potential micronutrient deficiencies to think about for people taking weight management medication, dietary sources of these nutrients, symptoms and signs of deficiency, and additional considerations. This list includes:

fat-soluble vitamins (A,D,E,K)
water soluble vitamins [B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), B12 (cobalamin), C (ascorbic acid)]
minerals (calcium, copper, iron, magnesium, potassium, zinc)

Why aren’t vitamins routinely recommended with weight management medications? The challenge is that we don’t have much data evaluating whether weight management medication increases the risk of micronutrient deficiencies, and if so, which micronutrients. As noted by the authors of this review article, we can only really look to data on micronutrient deficiencies in studies of people who have had bariatric surgery or who have been treated with very low calorie diets, and extrapolate that information to people taking weight loss medications. We need to keep in mind that micronutrient malabsorption can occur after some types of bariatric surgery due to changes made in the gut anatomy, which would not be expected with obesity medication. So, the risk of developing a micronutrient deficiency might be lower in people treated with medication than in people who have had bariatric surgery. We also need to be cautious in evaluating each individual’s health concerns if we are recommending vitamins, with one example being people with chronic kidney disease, where nutrient intake and goals need to be assessed with kidney function and other parameters in mind. Concomitant medications are important to assess, to ensure that vitamin regimens do not interact with, or interfere with absorption of medications.

Note that for orlistat (Xenical), because it works by decreasing dietary fat absorption, it can also reduce the absorption of fat-soluble vitamins. The product monograph for this medication therefore recommends vitamin supplementation.

BOTTOM LINE: People with elevated weight may be at higher risk of micronutrient deficiencies even before the treatment journey with weight loss medication begins. Assessing risk factors for nutrient deficiency, evaluating and advising on nutrition, and treating any pre-existing nutrient deficiencies are important. Even with a focus on eating well, it may be difficult for some people to maintain nutritional adequacy with weight management medication – especially for people who are having gastrointestinal side effects, greater suppression of appetite, or excessive weight loss. While data are lacking regarding weight management medication and whether or not they increase the risk of micronutrient deficiencies, it may be time to routinely consider vitamin supplementation. Each person should discuss potential vitamin supplementation with their health care professional, so that other health conditions or medications can be taken into appropriate consideration.

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