Nutritional deficiencies with GLP-1
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Nutritional deficiencies with GLP-1 refer to an insufficient intake or reduced stores of nutrients essential for the proper functioning of the body during treatment with glucagon-like peptide-1 receptor agonists, such as semaglutide or liraglutide, and dual-acting GIP/GLP-1 drugs, such as tirzepatide. These medications do not cause typical malabsorption syndrome, but they reduce appetite, decrease the amount of food consumed, and can cause gastrointestinal symptoms. Consequently, the diet may be too low in protein, vitamins, and minerals. The risk increases with rapid weight loss, a monotonous diet, chronic vomiting, pre-existing deficiencies, gastrointestinal diseases, and after bariatric surgery. The consequences may include, among others, muscle weakness, anemia, and deterioration of the condition of bones, skin, nails, and hair.
Nutritional deficiencies with GLP-1 - why they occur
GLP-1 receptor agonist medications increase feelings of satiety, reduce hunger, and affect the centers regulating food intake. Some preparations also temporarily delay gastric emptying. Studies have observed a reduction in spontaneous energy intake by up to approximately 20-40%. However, the drug itself does not "flush out" vitamins and minerals. The risk of deficiency results primarily from a smaller quantity and improper composition of the food consumed.
The most important mechanisms include:
- reduced total food intake, making it more difficult to meet the requirements for protein, vitamins, and minerals;
- early satiety, which favors skipping meals or consuming very small portions;
- nausea, vomiting, diarrhea, or constipation, which limit the tolerance of wholesome foods;
- changes in dietary preferences, sometimes leading to the elimination of meat, fish, dairy, or vegetables;
- rapid weight reduction, increasing the risk of lean body mass loss and telogen effluvium;
- pre-existing deficiencies prior to treatment, which are frequent in people with obesity despite excessive energy intake;
- comorbidities and medications, for example, metformin associated with the risk of vitamin B12 deficiency or proton pump inhibitors that limit its release from food;
- post-bariatric surgery status, inflammatory bowel disease, celiac disease, or chronic kidney disease, which require separate monitoring.
Current data do not allow for determining the exact incidence of deficiencies caused directly by GLP-1 therapy. It is a multifactorial risk, dependent on the patient's baseline status, the rate of weight loss, diet quality, and treatment tolerance.
Nutritional deficiencies on GLP-1 - which nutrients are most commonly lacking
The most likely abnormalities concern nutrients whose intake was already insufficient before treatment or decreased as a result of food restriction. Not every patient requires supplementation, and the diagnosis of a deficiency should be based on medical history, physical examination, and appropriately selected laboratory tests.
Nutrient | Main risk factors during therapy | Possible consequences |
Protein | small portions, aversion to meat or dairy, rapid weight loss | muscle loss, weakness, impaired healing, hair thinning |
Iron | low meat intake, heavy menstruation, previous bariatric surgery | anemia, fatigue, paleness, hair loss |
Vitamin B12 and folates | vegan diet, metformin, gastrointestinal diseases | anemia, glossitis, neurological disorders |
Vitamin D and calcium | low intake, low sun exposure, dairy restriction | impaired bone mineralization, muscle weakness |
Zinc | monotonous diet, chronic diarrhea, low intake of animal products | impaired healing, skin lesions, brittle hair |
Thiamine, vitamin B1 | prolonged vomiting, very low energy intake | neuropathy, cardiac disorders, Wernicke's encephalopathy |
Magnesium and potassium | vomiting, diarrhea, dehydration, diuretics | muscle cramps, weakness, cardiac arrhythmias |
Vitamins A, C, E, and K | diet low in vegetables, fruits, and fats, malabsorption | impaired skin function, immunity, vision, or coagulation |
Particular attention should be paid to inadequate protein intake, because during weight loss, not only fat tissue decreases, but also lean mass. The loss of muscle tissue may be exacerbated in elderly, inactive, chronically ill individuals, and those following a very low-calorie diet. Biotin and selenium are sometimes associated with hair health, but their routine supplementation without a confirmed deficiency is not justified. An excess of selenium can actually cause hair loss, and high doses of biotin interfere with the results of certain laboratory tests.
Nutritional deficiencies with GLP-1 - how they manifest on the skin and hair
The skin, hair, and nails react to an insufficient supply of energy and nutrients, but the observed changes are not specific. The same clinical picture can occur in thyroid diseases, anemia, androgenetic alopecia, inflammatory diseases, after an infection, or as a result of chronic stress.
The most common problem during rapid weight loss is acute telogen effluvium. A deficiency of energy, protein, iron, zinc, or vitamin D can prematurely shift a larger number of hair follicles from the growth phase to the resting phase. Diffuse, non-scarring hair loss usually appears only about 2–4 months after the triggering factor. It does not indicate a direct toxic effect of the medication on the hair follicle. Once the cause is resolved, the hair growth cycle usually gradually normalizes, although regaining density may take many months.
Possible signs of deficiencies include:
- dry, rough, or flaking skin;
- paleness of the skin and mucous membranes;
- cracked corners of the mouth and glossitis;
- slower wound healing and increased susceptibility to irritation;
- easy formation of petechiae or bruising;
- diffuse thinning and inhibited hair growth;
- dull, thin, and more brittle hair;
- brittle, splitting nails.
Patchy hair loss, scarring of the scalp, severe itching, pain, erythema, or scaling require a dermatological consultation, as they are not typical signs of a simple nutritional deficiency.
Nutritional deficiencies with GLP-1 - how to prevent them
Prevention should be started before initiating treatment. An assessment of dietary habits, comorbidities, medications taken, previous gastrointestinal surgeries, the rate of planned weight loss, and the risk of eating disorders is indicated. Laboratory tests are selected individually by a doctor. In patients with risk factors, they may include a complete blood count, ferritin and iron metabolism parameters, vitamin B12, folates, 25(OH)D, electrolytes, kidney and liver function, and in specific situations, also zinc, magnesium, or thiamine.
The basic principles of prevention are:
- consuming protein source products first, followed by vegetables, whole grains, and healthy fats;
- distributing protein across several meals and determining individual requirements with a dietitian;
- choosing nutrient-dense foods instead of products that primarily provide energy;
- regular fluid intake in small portions;
- gradually increasing the medication dose according to the doctor's recommendations and managing persistent gastrointestinal symptoms;
- resistance training 2–3 times a week, adapted to health status, in order to protect muscles and bones;
- monitoring the rate of weight loss, muscle strength, diet, and clinical symptoms;
- using supplements only after assessing indications, as they do not replace a diet, and an excess can be harmful.
Persistent vomiting, inability to take in fluids, fainting, confusion, palpitations, or progressive weakness require urgent medical evaluation. The medication dosage should not be changed on one's own.
In the case of severe hair loss, the basis of management is identifying and correcting the systemic cause. The procedures offered at Ambasada Urody to support scalp condition include scalp mesotherapy with mesococktails, biomimetic and tropocollagen mesotherapy, polynucleotides for hair, peptide therapy, platelet-rich plasma for hair, scalp microneedling, Regenera Activa, and carboxytherapy. These treatments act locally, including through biostimulation, controlled micro-injuries, or improving the scalp's microenvironment. However, they do not replenish systemic deficiencies of protein, iron, vitamins, or electrolytes and should not replace diagnostics. The selection of a procedure must be preceded by a consultation, as the effectiveness of individual methods depends on the diagnosed type of alopecia, and the evidence base is not equally strong for all the listed therapies.
