United States Department of Agriculture
Agricultural Research Service

National Nutrient Database for Standard Reference Legacy Release
Try FoodData Central Basic Report:  12220, Seeds, flaxseed a  b 
heading Nutrient Unit
Value per 100 g

tbsp, whole 10.3 g

cup, whole 42 g

tbsp, ground 7 g

tsp, whole 3.4 g

tsp, ground 2.5 g
Proximates Water g 6.96 0.72 2.92 0.49 0.24 0.17
Proximates Energy kcal 534 55 224 37 18 13
Proximates Protein g 18.29 1.88 7.68 1.28 0.62 0.46
Proximates Total lipid (fat) g 42.16 4.34 17.71 2.95 1.43 1.05
Proximates Carbohydrate, by difference g 28.88 2.97 12.13 2.02 0.98 0.72
Proximates Fiber, total dietary g 27.3 2.8 11.5 1.9 0.9 0.7
Proximates Sugars, total g 1.55 0.16 0.65 0.11 0.05 0.04
Minerals Calcium, Ca mg 255 26 107 18 9 6
Minerals Iron, Fe mg 5.73 0.59 2.41 0.40 0.19 0.14
Minerals Magnesium, Mg mg 392 40 165 27 13 10
Minerals Phosphorus, P mg 642 66 270 45 22 16
Minerals Potassium, K mg 813 84 341 57 28 20
Minerals Sodium, Na mg 30 3 13 2 1 1
Minerals Zinc, Zn mg 4.34 0.45 1.82 0.30 0.15 0.11
Vitamins Vitamin C, total ascorbic acid mg 0.6 0.1 0.3 0.0 0.0 0.0
Vitamins Thiamin mg 1.644 0.169 0.690 0.115 0.056 0.041
Vitamins Riboflavin mg 0.161 0.017 0.068 0.011 0.005 0.004
Vitamins Niacin mg 3.080 0.317 1.294 0.216 0.105 0.077
Vitamins Vitamin B-6 mg 0.473 0.049 0.199 0.033 0.016 0.012
Vitamins Folate, DFE µg 87 9 37 6 3 2
Vitamins Vitamin B-12 µg 0.00 0.00 0.00 0.00 0.00 0.00
Vitamins Vitamin A, RAE µg 0 0 0 0 0 0
Vitamins Vitamin A, IU IU 0 0 0 0 0 0
Vitamins Vitamin E (alpha-tocopherol) mg 0.31 0.03 0.13 0.02 0.01 0.01
Vitamins Vitamin D (D2 + D3) µg 0.0 0.0 0.0 0.0 0.0 0.0
Vitamins Vitamin D IU 0 0 0 0 0 0
Vitamins Vitamin K (phylloquinone) µg 4.3 0.4 1.8 0.3 0.1 0.1
Lipids Fatty acids, total saturated g 3.663 0.377 1.538 0.256 0.125 0.092
Lipids Fatty acids, total monounsaturated g 7.527 0.775 3.161 0.527 0.256 0.188
Lipids Fatty acids, total polyunsaturated g 28.730 2.959 12.067 2.011 0.977 0.718
Lipids Cholesterol mg 0 0 0 0 0 0
Other Caffeine mg 0 0 0 0 0 0

Footnotes
a  Up to 12 percent flax seed can safely be used as an ingredient in food.
b  Other phytosterols = 49.0 mg/100g; these include delta 5-avenasterol (21.2), campestanol (2.8), brassicasterol (1.1) and other minor phytosterols (23.9 mg).