When Should You Start Solids: 4 Months or 6 Months?

Starting solids is one of the biggest milestones in your baby's first year. If you're a parent of a baby approaching 4 months, you've probably heard conflicting advice: some say start solids at 4 months, while others recommend waiting until 6 months. So what's the right answer?

In this article, I'll explore the research behind both options, consider developmental readiness, and help you feel more confident about choosing what works best for your baby.

Why Is There Confusion About Starting Solids?

Whether it’s advice from your GP, maternal child health nurse, or your mum’s group, many Australian parents are told it’s okay to start solids around 4 months. But the World Health Organization (WHO) recommends exclusive breastfeeding until 6 months of age.

A two-month difference might not sound like much—but in a baby’s first year, that’s a big developmental leap.

What Do Australian Parents Actually Do?

Research gives us insight into real-life feeding practices across Australia:

• A 2020 study in South West Sydney found that by 17 weeks (just under 4 months), 13.6% of babies had started solids. By 26 weeks (around 6 months), 76.9% had started.
• A Queensland study showed that 44% of infants had begun solids by 4 months.

The studies also showed that certain factors influenced timing:

• Younger mothers, single mothers, and those returning to work earlier were more likely to start solids earlier.
• These trends reflect practical and personal considerations many families face.

But while the when is helpful to know, it doesn’t answer the big question:

What Does the Research Say: Is 4 or 6 Months Better?

Breastfeeding and Gut Health

The WHO recommendation to wait until 6 months is based on a 2012 study comparing exclusive breastfeeding for 6 months vs. introducing solids between 3–4 months.

Key finding:
Babies exclusively breastfed for 6 months had fewer gastrointestinal infections. However, there was no significant difference in growth or weight gain between the two groups.

It is also worth noting, the study focused on exclusively breastfed infants, so results may not apply equally to formula-fed babies.

Solids and Obesity Risk

A 2015 paper explored links between the timing of solids and childhood obesity. It found:

• An increased risk of obesity when solids were introduced before 4 months
• No significant difference in obesity risk between babies who started solids between 4–6 months and those who started after 6 months

Food Allergies and Early Exposure

With 1 in 10 infants in Australia affected by food allergies, many parents worry about when to introduce common allergens.

A 2018 meta-analysis found:

• Starting solids before 4 months didn't increase the risk of allergies, but did increase the risk of food sensitivities
• Early introduction of eggs (4–6 months) lowered the risk of egg allergy
• Early exposure to peanuts (between 4–11 months) reduced the likelihood of peanut allergies

That said, researchers concluded that the findings weren't strong enough to change the current age guidelines on starting solids.

So... When Should You Start?

Given the research doesn’t clearly favour 4 or 6 months, one of the most important factors to consider is developmental readiness.

Signs Your Baby May Be Ready for Solids

Look for these cues, which usually develop between 4–6 months:

• Good head and neck control
• Can sit upright with support
• Shows interest in food (watches you eat or reaches for food)
• Opens mouth when offered a spoon
• Has lost the tongue-thrust reflex (doesn’t push food out with their tongue)

 

Why Solids Before 12 Months Matter

Breastmilk or formula should remain your baby’s main source of nutrition until 12 months. But solids play an important complementary role by:

• Providing additional nutrients—especially iron, which babies start to need more of after 6 months
• Helping babies develop eating skills, including chewing and swallowing
• Exposing babies to different tastes and textures, which may reduce the risk of fussy eating
• Supporting oral motor development, important for speech and language later on

Research backed tip: When you do start solids, include iron-rich foods like iron-fortified cereals, pureed meats, lentils, and leafy greens.

The Bottom Line

There is no one-size-fits-all answer to when to start solids. What’s most important is to:

• Wait until at least 4 months old
• Look for signs of developmental readiness
• Talk to your child health nurse or GP if you’re unsure

Every baby is different—and so is every family. Take into account your child’s readiness and your personal circumstances, and trust that with the right information, you’re making a good choice.

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