From the Guidelines
Low alkaline phosphatase (ALP) levels can be present in gastric bypass patients at any time, particularly due to nutritional deficiencies that develop after bariatric procedures. This occurs primarily due to zinc deficiency, a common cause of low ALP in these patients, as zinc is a necessary cofactor for ALP enzyme activity 1. Other contributing factors include vitamin D deficiency, calcium malabsorption, and protein malnutrition, all of which can result from the altered digestive anatomy following gastric bypass.
Key Factors Contributing to Low ALP Levels
- Zinc deficiency: a necessary cofactor for ALP enzyme activity
- Vitamin D deficiency
- Calcium malabsorption
- Protein malnutrition
Patients who have undergone malabsorptive procedures like Roux-en-Y gastric bypass are at higher risk compared to purely restrictive procedures 1. Regular monitoring of ALP levels along with nutritional parameters is recommended for gastric bypass patients, with supplementation of zinc (typically 15-30 mg daily), vitamin D (1,000-5,000 IU daily), calcium (1,200-1,500 mg daily), and adequate protein intake (60-80 g daily) often necessary to address these deficiencies.
Recommendations for Gastric Bypass Patients
- Regular monitoring of ALP levels and nutritional parameters
- Supplementation of zinc, vitamin D, calcium, and adequate protein intake
- Multidisciplinary evaluation and intervention for management of comorbidities and long-term follow-up 1. Low ALP levels may not cause obvious symptoms but can potentially impact bone health, immune function, and other metabolic processes if the underlying nutritional deficiencies are not addressed.
From the Research
Low ALP Levels in Gastric Bypass Patients
- Low Alkaline Phosphatase (ALP) levels can be present in gastric bypass patients at any time, as micronutrient deficiencies are common in patients undergoing gastric bypass 2.
- The study found that mean plasma zinc, erythrocyte membrane alkaline phosphatase activity, and the size of the rapidly exchangeable zinc pool decreased after Roux-en-Y gastric bypass (RYGBP) 2.
- Zinc status is impaired after RYGBP, despite the finding that dietary plus supplemental zinc doubled recommended zinc intakes in healthy persons 2.
- However, there is no direct evidence that low ALP levels are specifically related to gastric bypass patients, as most studies focus on zinc deficiency and hypophosphatasia in general populations 3, 4, 5, 6.
Related Conditions
- Hypophosphatasia (HPP) is a condition that may be associated with low ALP levels, and it can be misdiagnosed as osteoporosis 5.
- Low ALP levels can be a screening tool for HPP, and it is essential to recognize this condition to avoid misdiagnosis and mistreatment 5.
- A study found that 9% of patients attending an osteoporosis clinic had low ALP levels, and 3% of these patients were diagnosed with HPP 5.
Gastric Bypass and Nutrient Deficiencies
- Gastric bypass surgery can lead to nutrient deficiencies, including zinc deficiency, due to reduced intake and absorption 2, 3.
- The British Obesity and Metabolic Surgery Society recommends monitoring zinc levels routinely following gastric bypass, while the American guidance reserves it for patients with specific findings 3.
- A systematic review found that clinically relevant zinc deficiency is rare after RYGB, and routine monitoring of zinc levels may not be necessary for asymptomatic patients 3.