Basic Guidelines

Children with SMA tolerate different amounts of fluids, calories, protein, fat, and nutrients than unaffected children. Over-feeding is a common problem and can interfere with movement and optimal health. Providing nutritious carbohydrates, amino acid protein, and the minimum amount of fat necessary to meet the essential fatty acid requirement will give the best results. Below are basic guidelines that should apply to most children with SMA.

Fluid intake:

Adequate fluid intake is important. Some children tolerate more than others and parents should give as much fluid as comfortably tolerated. If total fluid intake is higher than 125ml/kg, be sure that sodium and potassium intake is closely monitored with lab testing.

The ranges below are guidelines that most children tolerate. Flushes should be included in total fluid calculation.

• Age 1-3:   115ml-125ml/kg/24hrs.
• Age 4 and over:  ?-90ml-?/kg/24hrs. As children grow, the ratio of fluid to weight gradually decreases but should still be as much as tolerated. In other words, depending on a child’s weight, maximum fluid intake may fall below 90ml/kg. Total fluid should include water, juices, and baby foods.

Calorie intake over age 1:

• Over age 1: 60-75cal/kg/24hrs.  To calculate weight in kg, divide weight in pounds by 2.2
• 7-10 calories/cm  To calculate height in centimeters, multiply height in inches by 2.54
• Over time, the ratio of calories to weight gradually decreases with weight gain, therefore, a growing older child’s intake will be less calories/kg. In addition, when growth is finished, calorie requirements are lower.

The standard weight for height charts and dietary recommendations are NOT appropriate for children with very reduced muscle mass, as in SMA. Because most calories are required for muscle metabolism, many of our children will tolerate approximately 60% of the daily calories recommended for their age. In SMA, a child’s weight should be 3 or 4 standard deviations below length.

Protein intake:

1-1.3g/kg/24hrs. As children grow older and weight increases, protein intake will fall below 1g/kg.

Protein in amino acid form is very quickly absorbed and utilized as an energy source. High amounts of free form amino acids should never be given over a short period of time to children with reduced muscle mass. To ensure adequate amino acid protein is being given, a quantitative amino acid lab profile should be run 1 to 2xs/year, or more often in very young children, those just starting the diet, or during illness or other stress. Double diluting amino acid formulas (2 times more than package directions) is important to avoid toxicity.

Fat intake: 10-20% of calories from fat- Keeping fat % of calories low will often alleviate g.i. distress. Many children will tolerate breast milk fat in higher amounts than other fats. An essential fatty acid profile will indicate if intake is adequate, keeping in mind that reference ranges are based on typical diets containing much higher amounts of fat.

Because many patients with SMA may have a defect in fatty acid oxidation, or the breaking down of fats for energy, most children are healthier on very low fat diets. Most dietary fat is metabolized by skeletal muscle. With often 10% or less of normal muscle mass, the fat requirement in SMA should be calculated much lower than standard recommendations.