Breastfeeding causes iron deficiency?

Symptoms :

Anemia includes pale skin, tiredness, rapid heartbeat, irritability, loss of appetite, brittle nails, swollen tongue, decrease immune function, which increases susceptibility to infection. At times, is common for a baby with anemia not to have any symptoms at all.

To determine whether the baby is anemic, a blood test is required to measure levels of hemoglobin and hematocrit ( percentage of red blood cells in the blood )

Is Anemia dangerious ?

Possible as the child could suffer permanent mental ( normal thinking or processing skills )and physical problems ( normal activity or movement skills). They also more susceptible to lead poisoning and infection.
Children are at high risk between 9 and 24 months. Babies who were born prematurely are at higher risk since they get the majority of the iron stores during the last trimester of pregnancy.

How to prevent Anemia?

The iron in breast milk is absorbed three times better than the iron in formula. Indeed, baby  will absorb an average of 50-70% of iron in breastmilk compare that to the 3-12% they absorb from cow’s milk formula. After the baby is six months of age, solids food are ADDED to breastfeeding, additional iron in the form of fortified cereals and other iron-rich foods. Noted that the additional food do not replace "breastfeeding or stop breastfeeding". Breastmilk is still the main source of nutrition for babies after the first 6 months because it still contains all those hundreds of nutrients, cells and factors.

4-6 months baby , you can start with pureed food like  sweet potatoes, squash, apples, bananas, peaches, peas or semi-liquid iron-fortified cereal. Continue breast milk or formula. 

6-8 months baby, you can start feeding pureed, strained fruits (banana, pears, applesauce, peaches), strained vegetables (avocado, well-cooked carrots, squash, and sweet potato), Small amounts of unsweetened yogurt, meat (chicken, pork, beef). Continue Breast milk or formula.

8-10 months baby , try small amounts of soft pasteurized cheese and cottage cheese, Mashed fruits and vegetables (bananas, peaches, pears, avocados, cooked carrots, squash, potatoes, sweet potatoes), small amounts of protein (eggs; pureed meats, poultry, and boneless fish; tofu; well-cooked and mashed beans with soft skins like lentils, split peas, pintos, black beans) and Iron-fortified cereal (barley, wheat, oats, mixed cereals). Continue breast milk or formula.

Offer plenty of fruits and vegetables that are rich in vitamin C, such as kiwi, avocado, and cantaloupe). Vitamin C helps the body absorb iron. If you can't breastfeed, use iron-fortified formula.

Lastly, if you’ve done what you can and your baby is still iron-deficient, iron supplementation can fill a real and important purpose provided it’s not overused. Consult a doctor for prescription for iron supplementation. Check out what is Hemochromatosis? is the disease resulting from significant iron overload. 

Iron in the Vegan Diet by Reed Mangels, Ph.D., R.D. also has some great info on iron-rich foods.

Dietary Sources of Vitamin C

Food, Standard Amount	Vitamin C (mg)	Calories
Guava, raw, ½ cup	188	56
Red bell pepper, raw, ½ cup	142	20
Red bell pepper, cooked, ½ cup	116	19
Kiwi fruit, 1 medium	70	46
Orange, raw, 1 medium	70	62
Orange juice, ¾ cup	61 to 93	79 to 84
Green bell pepper, raw, ½ cup	60	15
Green bell pepper, cooked, ½ cup	51	19
Grapefruit juice, ¾ cup	50 to 70	71 to 86
Vegetable juice cocktail, ¾ cup	50	34
Strawberries, raw, ½ cup	49	27
Brussels sprouts, cooked, ½ cup	48	28
Cantaloupe, ¼ medium	47	51
Papaya, raw, ¼ medium	47	30
Kohlrabi, cooked, ½ cup	45	24
Broccoli, raw, ½ cup	39	15
Edible pod peas, cooked, ½ cup	38	34
Broccoli, cooked, ½ cup	37	26
Sweet potato, canned, ½ cup	34	116
Tomato juice, ¾ cup	33	31
Cauliflower, cooked, ½ cup	28	17
Pineapple, raw, ½ cup	28	37
Kale, cooked, ½ cup	27	18
Mango, ½ cup	23	54