Before you make any significant changes to your diet, even if you think your changes will be healthy, you should consult with your physician or a registered dietitian.  Many health conditions and prescription medications must be taken into account when planning a diet plan, so consulting with a professional will keep you safe and healthy. A registered dietitian is an expert who has completed education, training, and supervision in the field of nutrition. Dietitians can help you determine a healthy diet and fitness plan that will account for any health conditions you have and medications or supplements you take. Implementing changes to what you're eating on a daily basis in a gradual fashion will help your body adjust appropriately. Sometimes altering your diet can cause unpleasant symptoms as your body adjusts to the new foods and eliminates the remnants of the old foods. Making gradual changes will also ease any cravings you may feel for what you used to eat, such as sugary treats or salty snacks. Folate is a water-soluble B vitamin; folic acid and food folate are both sources of folate. Folate deficiency can cause your bone marrow to have difficulty making enough platelets.  The recommended daily intake of folate varies, but adults should usually have between 400mcg and 600mcg a day. A full list of recommended daily allowances by age can be found at the National Institutes of Health website here.  Beef liver, leafy and dark green vegetables, legumes, fortified cereals, and nuts are good sources of folate. If you don't consume enough vitamin B12, your bone marrow may have difficulty making enough platelets. Vitamin B12 is also essential to red blood cell formation.  The recommended daily intake of B12 varies, but adults should usually have between 2.4mcg and 2.8mcg daily. A full list of recommended daily allowances by age can be found at the National Institutes of Health website here. B12 is commonly found in animal products, so vegetarians and vegans may need a supplement. Good dietary sources of B12 include shellfish, beef liver, fish, fortified cereals, and dairy products. Foods containing probiotics, such as yogurt and fermented foods, may help improve the immune system. Probiotic bacteria may also help regulate the immune system, which may help people with autoimmune disorders (a common cause of low platelet count). Good sources of probiotics include yogurt with live cultures, kefir (fermented milk), kimchi (Korean fermented vegetables), and fermented soy products such as tempeh, miso, and natto. Eat a wide variety of foods, particularly different fruits and vegetables. Eating widely will help your body get all of the nutrients it needs. In addition, try to eat locally; buy produce when it's in season in your local area. Not only will you be getting the freshest produce, but there's also less chance it has any additives or pesticides in order to keep it fresh for transport across long distances.  Visit the grocery store often to shop for fresh produce because the nutrient content decreases with time. Instead of doing all of your shopping on one day, plan to go to the store a few times per week. Always choose fresh varieties over frozen and canned foods. For example, if you have the choice between fresh corn on the cob and canned corn, go for the fresh. Replace these foods with whole, unprocessed food. For example, eat whole grain cereals, brown rice, and whole wheat products. Again, read the labels of products as you shop. Reduce the amount of white flour, white rice and processed foods you consume because  these have been and "refined", or stripped of their nutrient-rich coating. Be sure as well to reduce the amount of white sugar you consume, as well as other sweeteners, such as fructose, corn syrup and honey. Cut back as well on fruits with lots of sugar, including mangoes, cherries, and grapes, as well as sugary fruit juices. Sugar can contribute to promoting high levels of acidity in the body.
Consult with a doctor or registered dietitian. Make any changes to your diet slowly. Eat foods containing folate. Eat foods containing B12. Eat probiotics. Eat a balanced diet of fresh food. Eliminate processed and sugary foods.