How To Start Your Baby on Solids And Support Their Development

The introduction of solids marks a pivotal time in your baby’s gut and immune development. At around 6 months, as your little one transitions from a milk-based diet to one with a wide variety of foods, you’ll start to see a shift in your baby’s gut microbes. 

Like breastmilk, solid food helps shape which microbes flourish and which do not.

Breastmilk is a major source of human milk oligosaccharides, or HMOs. HMOs are not digested by your baby but can be broken down by beneficial gut bacteria like Bifidobacterium, which we like to see dominating the baby's gut in the early months. Plant-based foods contain different types of fibers -fructooligosaccharides, inulin, cellulose, etc.- that feed a wide range of beneficial gut bacteria. This is very important to help diversify a baby's gut microbiome, nudging it towards an adult-like composition. 

In this blog post, you’ll learn how to start your baby on solids, when is the best time to do so, and which foods best support the development of your baby’s microbiome.

‍Interested in learning how to handle common allergens? Go to our blog post on food allergen introduction. Spoiler alert: early introduction of allergenic foods can actually decrease the risk of developing food allergy.

When can babies eat solid food?

It’s just as important to look at your baby as it is to look at a calendar when deciding when to start solid foods. When the gastrointestinal (GI) tract is sufficiently mature and coordinated, babies typically signal to their parents that they want to be fed. At first, they will show interest when you’re eating. Later they will almost demand to be fed.

You can decide to start whenever your baby is ready to start. This will often happen at about the 6-month mark. If it seems to be taking longer, be sure to discuss timing with your pediatrician.

The American Academy of Pediatrics (AAP), the CDC, the World Health Organization, UNICEF, the European Society for Pediatric Gastroenterology, Hepatology and Nutrition along with the National Health and Medical Research Council Infant Feeding Guidelines of Australia all recommend starting solids at around 6 months old. 

For the sake of nutrition and protecting against food allergies, the 2020 USDA Dietary Guidelines for Americans (DGA) recommend exclusive breastfeeding for a baby’s first 6 months - if possible - with the introduction of solid food at around 6 months of age. This is in line with the global recommendation for exclusive breastfeeding during a baby’s first 6 months.  

Some important signs of baby readiness include:

• Sitting with little or no support
• Good head control
• Opening their mouth and leaning towards food
• Swallowing food rather than pushing it back out
• Bringing objects to their mouth
• Trying to hold small objects

While your baby may be ready for solids a little earlier or a little later than 6 months, the consensus is that solid food provides high-demand nutrients to the baby (and the microbiome) that will be important for the second half of the first year.

Introduce solid foods when your baby is ready, typically at 6 months.

What is the best baby food?

At around 6 months it’s time to start thinking about the first solid foods that you would like to offer.

One thing to keep in mind for the best first food for a baby is that—truly—every bite counts. Since portions will be very small and filling for tiny tummies, it’s a good idea to avoid foods lacking nutrient density and instead aim for whole foods that are rich in natural nutrients and flavors. 

For those very first bites, you may want to enjoy a simple family meal. Choose a whole food that is simple and colorful as your baby’s color vision has recently matured; perhaps an avocado, banana, or baked sweet potato. Let your baby touch the produce, smell the produce, and watch as you peel and eat. Then take some of the same item, perhaps mixing a bit with something familiar (breastmilk or formula) by mashing it in with a fork. Watch your baby open their mouth - and take pictures!

Your pediatrician may suggest starting with processed baby cereal. You may want to avoid daily use of rice-based cereals due to potentially high levels of arsenic [1]. Whole-grain oats may be a better choice.

You’ll want to offer your baby simple, home-cooked foods. These may be foods you’re already eating, mashed, or cut in a way that can be eaten without choking. 

Sounds simple, right? 

Feeding your baby can be a simple and easy experience as long as you know which foods to focus on and some basic principles on approach. In particular, aside from focusing on nutrient-dense foods, it’s important to start introducing allergens early. Research shows that this can reduce the risk of food allergies and sensitivities later on [2], [3].

• Emphasize fruits and vegetables: These foods feed your baby’s microbiome and are a source of antioxidants, like vitamin C, which improves iron bioavailability.
• Emphasize meat, egg, liver, and seafood: These foods provide a number of nutrients that tend to run low, including iron, zinc, choline, and long-chain omega-3 fatty acids.
• Regularly include some dairy products: For example, baked dairy, yogurt, and cheese all offer exposure to cow milk protein, a major allergen. Keep in mind that too much cow dairy is a common cause of iron deficiency in babies.
• Regularly include some grains, legumes, and seeds: These foods feed your baby’s microbiome and many of them - like wheat, soy, and peanut - are major food allergens.
• ‍Avoid these foods: Honey until 12 months, caffeinated drinks, juice and added sugar, added salt, and foods with additives, coloring, or emulsifiers.

Best baby food recipes

Finding the right recipes to feed your baby is hard, so we did it for you. You may consider checking out Solids Start’s recipes for first foods. You may even consider trying one of the recipes below.

Butternut Squash Puree

‍Why we like it

• Butternut squash is high in vitamin A, which helps regulate cell growth, eye development, and has anti-inflammatory properties that help the immune system function [4].
• It’s high in carotenoids, which can act as antioxidants and can be converted to vitamin A in the body [5].
• It’s high in fiber [6], which helps keep your baby's gut healthy and prevents constipation. It also feeds your baby's gut microbiome.

Ingredients

• 1 small butternut squash
• 1 tablespoon olive oil

‍Directions

1. Preheat your oven to 400 degrees Fahrenheit. Place the squash on a cutting board and cut it lengthwise. Halve the squash and scoop out all the seeds and pulp. 
2. Sprinkle olive oil over the flesh of the butternut squash. Place parchment paper on a baking sheet, and place the cut butternut squash flesh-side down. 
3. Bake the butternut squash in the oven for about 45 minutes until it’s very tender.
4. Allow the squash to cool before removing the surrounding skin. 
5. Add the baked flesh of the butternut squash to a food processor or blender and blend. You may even consider adding some breastmilk or formula. Process the butternut squash until the consistency is just right for your baby's chewing ability.
6. Serve and allow your baby to enjoy their meal. You may also consider storing it in an airtight container for later.

Green pea, spinach, and apple puree

Why we like it

• Contains not just one, but two vegetables to begin introducing to your baby. Children who express a dislike for a vegetable can still develop a taste for it [7]. Continuing to expose your baby to vegetables – sometimes even up to 15 times – can help bring a fondness to these foods.
• Green peas are packed with protein (although they lack the essential amino acid methionine) [8], and are rich in polyphenols [9], which provide several health benefits.
• Spinach is a great source of vitamin K, which helps with blood clotting and bone development. It also has a high amount of iron; though the presence of other food components, such as oxalates, decreases iron’s bioavailability. Bioavailability is the body's ability to absorb nutrients, like iron.
• Apples add a little sweetness to the recipe but are also high in vitamin C, which helps absorb more iron [10]. They are also a good source of dietary fiber. Fiber helps keep your baby's digestive tract healthy and prevents constipation. It also feeds your baby's gut microbiome.

Ingredients

• 1 cup frozen green peas
• 1 cup spinach
• 1 medium sweet apple

‍Directions

1. While thawing the frozen green peas, place a steamer basket into a pot and add enough water to cover the bottom of the steamer basket. Begin to bring the water to a boil. Wash the spinach and apple. On a cutting board, slice the apple and remove the skin.   
2. Once the water has come to a boil, add the spinach, apple, and green peas into the steamer basket and cover the pot. Steam for around 10 minutes. 
3. After cooling the ingredients, add the steamed spinach, green peas, and apples to a food processor or blender and blend. You may even consider adding some breastmilk or formula. Blend the ingredients until the consistency is just right for your baby's chewing ability.
4. Serve and allow your baby to enjoy their meal. You may also consider storing it in an airtight container for later.

How to feed your baby

Responsive feeding is a style of feeding that responds to your baby’s cues. It encourages your baby to exercise agency during feeding, in response to their own needs. It’s a child-centered approach that not only can bring more ease at mealtimes but also has been found to promote adventurous eating behaviors [11].

Non-responsive feeding can override a baby’s hunger and satiety cues, which may later impact appetite regulation and growth that could lead to obesity and a potentially disordered relationship with food [5].

While responsive feeding is similar to baby-led weaning (BLW) in that the approach is baby-led, parents can practice responsive feeding at any age. Responsive feeding isn’t limited to a certain food texture or to the introduction of solid foods. 

Whether breastfeeding or bottle-feeding, responsive feeding begins with your baby’s first feed and continues as you introduce your baby to solids [12]. While your baby’s cues may change as they develop, the principles of responsive feeding can be applied to your baby as a newborn, toddler, or even during “picky” periods in a school-age child. 

• Get acquainted with and respond predictably to hunger and satiety cues. This means plenty of eye contact and checking in. 
• Avoid using food to calm or soothe your baby when they are not hungry.
• When first beginning solid foods, offer a range of options of flavors and textures while avoiding added sugar, processed foods, added salt, additives, coloring, and emulsifiers. 
• Provide the structure for your child to eat and let your child decide if and how much they would like to eat. Avoid positive or negative pressure to control how much your child eats. 
• Model the eating behavior you want to see and join your baby during mealtimes.

One of the most common obstacles for parents when transitioning to solid foods is giving up too soon. This can happen when a baby has a negative response to a food, such as a skin reaction, or if a food is rejected more than a few times. 

Remember that all exposure counts. A nibble, a lick, or simply the feeling of food between the palm and the fingers is a form of positive exposure.

Which solid foods are best for the baby’s gut microbiome?

While the consensus is that breastfeeding your baby until 6 months is ideal, it’s worth noting that the baby gut microbiome goes through three distinct phases of development [13]. In this blog post, we will focus on the first phase - or “developmental phase” - which runs from 3 months to 14 months old. 

Breastmilk - whether exclusively breastfed or partially breastfed - is one of the most important factors influencing your baby’s microbiome structure. Breastfed babies receive 27.7% of their gut bacteria from breastmilk and 10.4% from areolar skin during the first month of life [14]. Breastfeeding is linked to higher levels of Bifidobacterium species, like B. infantis, B. longum, B. breve, and B. bifidum. Bifidobacterium are bacteria that normally colonize the infant gut and are often considered the “good” bacteria, because they produce important nutrients called short-chain fatty acids, and help the immune system develop in a healthy way. 

Breastmilk supports Bifidobacterium because it has a unique nutritional composition. HMOs are complex sugars in breastmilk that a baby cannot digest, but gut microbes like Bifidobacterium can. 

While the introduction of solid foods does initiate a significant shift in the baby’s microbiome, complete weaning - or no longer giving your baby breastmilk - has an even bigger impact and drives the maturation of the baby gut microbiome [15]. Bifidobacterium will remain prominent in the baby gut, even with the introduction of solids, up until breastfeeding is ceased [14], [16].

Eventually, however, it’s important for the gut microbiome to begin to diversify. Diversification at the right time, typically around 6 months, helps make the microbiome more robust to perturbation as a baby becomes more mobile and their environmental exposures increase and influence neurological development [17]. The introduction of new dietary fibers and other food components can shift your baby's gut microbiome towards a more mature adult-like gut community. This can mean increased levels of bacteria other than Bifidobacterium that make short-chain fatty acids (SCFAs) [18].

To track your baby’s gut microbiome development, it’s a good idea to take a gut sample before 6 months, and then resample at around 6 months old and again when your baby reaches 12 months old.

Carbohydrates

Carbohydrates include both simple and complex sugars, such as starch and fiber. For the most part, simple sugars are digested and then absorbed in the small intestine, whereas complex sugars travel through the gut relatively undigested until reaching the colon, where they are fermented by gut microbes and act as prebiotics. 

Prebiotics selectively feed helpful microbes and in turn, benefit overall health. They are defined as “nondigestible food ingredients that beneficially affect the host” [15].

Prebiotics include:

• HMOs found in breastmilk
• Fructooligosaccharides (FOS) 
• Galactooligosaccharides (GOS)
• Insoluble dietary fiber, like beta-glucans from oats
• Soluble dietary fiber, like pectin and inulin

Different prebiotics will influence the growth of different microbial communities [16]. This is one reason why offering a variety in first foods is so important. It’s also worth noting that baseline dietary differences - whether a baby is fed breastmilk or formula - can significantly influence this trajectory [19].

An important by-product of prebiotic fermentation from gut microbes is SCFAs, such as acetate, butyrate, and propionate. Butyrate is the dominant energy source for the cells that line the colon [20]. SCFAs can also reduce the acidity - or pH - of the gut and protect against large numbers of unwanted microbes. They also interact directly and indirectly with cells in the immune system and reduce inflammation [21]. 

Foods high in prebiotics that diversify and increase the richness of the baby’s gut microbiome:

• Legumes
• Whole grains
• Fruits
• Vegetables

Fat

Fat is a macronutrient that includes monounsaturated fatty acids, polyunsaturated fatty acids, and saturated fatty acids. Ideally, the percentage of energy from fat in a baby’s diet when beginning solids is high; roughly 41% - 44% at 6 to 9 months to mimic the composition of breastmilk. This is important since it will aid the baby in adjusting to solids [22].

Foods such as meat, egg yolk, fatty fish, and dairy are not only a source of fatty acids but also important fat-soluble vitamins like vitamins A, D, and K. If breastfeeding, the fatty acid profile of breastmilk can be modified with diet. 

When it comes to the baby microbiome, some forms of dietary fat can reduce the levels of bacteria and have a bactericidal effect [22].

For example, one study looked at the potential benefits of a fish and safflower oil blend on the gut bacteria of preterm babies [23].  Researchers found lower levels of proinflammatory unfriendly bacteria in the group receiving the fatty acid blend compared to standard nutritional therapy. Beyond brain development and immune support, researchers suggest that long-chain omega-3 fatty acids may improve the structure and function of the baby microbiome, particularly in premature babies with necrotizing enterocolitis. 

Foods high in healthy fats:

• Fish
• Seafood
• Fish oils

Iron

Iron is possibly the most talked-about micronutrient of a baby’s first 1000 days. This is because iron deficiency is a common cause of anemia that negatively impacts babies’ motor, language, and cognitive development [24]. 

In other words, iron supports brain development. 

However, problems can arise in the baby gut microbiome because unabsorbed iron may lead to a decrease in helpful bacteria and an increase in potentially unfriendly bacteria while promoting inflammation. For example, in some cases, unabsorbed iron stimulates the virulence and growth of unfriendly bacteria, like Escherichia coli [25].

Heme iron, found in meat, is more bioavailable and easier for a baby to use than non-heme iron [26], found in both non-animal foods as well as supplements. What’s more, the benefits of meat as a first food extend to a baby’s microbes. 

A recent study shows that babies consuming beef as a first food saw no decline in Bifidobacterium and greater species richness after 4 weeks compared to babies eating iron-fortified cereal [27]. Other studies have found that meat as a first food for breastfed babies significantly increases levels of butyrate-producing Clostridium group XIVa [28].  

If meat isn’t an option, you may be able to support iron absorption by offering fortified cereals with fruit rich in vitamin C. 

Foods high in iron:

• Shellfish 
• Liver 
• Beef
• Lamb
• Canned sardines

Zinc

Zinc is a mineral that supports immune and intestinal health. Similar to iron, zinc is easier to absorb when it’s sourced from meat. This is because phytates - compounds found in whole grains, pseudocereals like quinoa, and legumes - reduce the bioavailability of minerals, including zinc [29].  

However, supplemental zinc doesn’t have the same deleterious effect on the gut microbiome as supplemental iron. For example, in a study with babies ages 2 - 36 months old with antibiotic-associated diarrhea and pneumonia, researchers compared the effects of zinc given with probiotics versus probiotics alone [30]. The combined treatment was found to increase Bifidobacterium while decreasing levels of E. coli. 

Another study with 6-month old babies revealed that fortified cereals - containing both iron and zinc - provided greater benefits than iron alone, since zinc appeared to counteract the unwanted effects of iron fortification on the gut microbiome [28].

Foods high in zinc:

• Oysters (but make sure they are cooked!)
• Crab
• Beef
• Lobster

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