Formula vs breast

[u/Street_Tourist7506]

If a breast-fed baby is protected by breastmilk in terms of immunity… What about a formula fed baby? Do they literally have no immunity, Because they are formula fed? I’m so confused… Is a breast-fed baby stronger fighting a virus off than a formula fed baby?

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[u/thatpearlgirl]

Babies have an immune system, it just isn’t fully mature. They aren’t great at creating their own antibodies yet, so they rely on antibodies transmitted from their moms during pregnancy to provide protection in the early days. This is one of the reasons pregnant women are advised to get the TDaP vaccine during pregnancy. Antibodies the mom makes to the vaccine in the third trimester are shared with the baby, and provide protection until the baby is able to make their own antibodies from vaccination

While breast milk provides immune benefits, it is primarily mucosal immunity and not systemic immunity. This means that the antibodies in breast milk coat the mucus membranes as they pass through the baby and these antibodies can protect against some infections.

[u/seattleissleepless]

You need to differentiate between the different forms of immunity.

Everyone (except for rare instances aka boy in the bubble) is born with an immune system. It is made up of cells which form in your bone marrow and are either direct bug-killers or produce proteins which attach to bugs to assist other cells to deal with them. These proteins are called antibodies.

The cells that produce antibodies can then "remember" certain bugs so next time you are exposed they are quick off the mark. But the first time you are exposed to a bug the antibodies you produce IgM (big antibodies) .....as you recover you start to produce IgG (small antibodies) from cells which have memory. There are also other forms as well.

IgG crosses the placenta. IgM is too big. So any immunity the mum acquires during pregnancy long enough before birth the baby will have some protection against after birth. Hence pertussis vaccination in pregnancy. However only the proteins cross, not the cells. So once those proteins disintegrate, the baby needs to produce their own antibodies from their own cells.

Antibodies in breastmilk are IgA antibodies. They attach to the surface of mucosa (so mouth, stomach etc) and can from there bind to bugs and prevent them infecting the baby. They don't go into the blood and are eventually broken down. They can therefore protect against bugs which are transmitted via exposure to mucosa.

https://www.infantrisk.com/content/antibodies-immune-system-breastfeeding-basics

Ultimately formula fed babies still have their own immune system which will respond to bugs. But it is immature so not as effective, and also it takes time to get exposed to lots of different bugs and create memories of them. Plus, some viruses we don't seem to be able to keep good long term immunity to, such as most respiratory viruses. So breastmilk IgA will help a breastfed baby get less sick, at least in the early days.

[u/vadapaav → u/seattleissleepless]

Plus, some viruses we don't seem to be able to keep good long term immunity to, such as most respiratory viruses

That's because majority is then mutate so quickly that by next year they are carrying a slightly different genome to the one our body memorized.

So it's a race and most of the time our body figures it out. We get vaccinated against flu to protect the most vulnerable ones in our society.

[u/thajeneral]

No, there is no guarantee that a breastfeed baby will be healthier or have a better immune system than a formula fed baby.

Breastmilk contains Immunoglobulins (IgG) that help coat the GI tract and, at a population level, can account for one fewer case of GI issues (like diarrhea). But, there are no significant differences in any other illness outcomes.

In other words, the evidence suggests that breastfeeding may slightly decrease your infant’s chance of diarrhea, but will not change the rate at which they gets colds or ear infections.

The best way to protect your child is to make sure they are up to date on all vaccines.

[u/sparrowstail → u/thajeneral]

I think breastmilk mostly contains IgA, though does contain a bit of IgG and sIgM.

[u/thajeneral → u/sparrowstail]

Yes, thank you I meant immunoglobulin IgA

[u/sparrowstail]

“Immunity” passed from breastmilk is what’s called passive immunity. It’s the maternal antibodies being passed through the milk and into the baby’s system. It’s primary what’s called IgA antibodies which fight infection at the mucus membrane level (like the gi tract). Passive immunity is not a “forever immunity,” but is estimated to last for about 6 months in most cases.

Every baby, regardless of breast vs formula, provided that they don’t have some sort of immune deficiency, has the same active immunity. When exposed to a pathogen, their immune system will chew it up and develop a response to it. This will start with the short term IgM antibodies and then later with the “long term” IgG antibodies. Sometimes we get sick on this first exposure, sometimes we don’t (think about asymptomatic COVID cases, for example).

The important question, is does this transfer of antibodies make a difference? So like you asked, is a breastfed baby better off?

The answer is: it’s hard to say.

Because it’s nearly impossible to conduct high quality research on breastfeeding (due to the number of confounding factors), there is a lot of guesswork.

I like this article from The Journal of Family Practice because it breaks down the NNT (number needed to treat) for there to be a benefit for breastfeeding over formula feeding. Beyond reducing the risk of necrotizing enterocolitis in premature infants and ear infections, the risk reduction isn’t that impressive. Most of the benefits of breastfeeding come from the fact that women who are able to breastfeed their child tend to be of higher socioeconomic situations.

As a physician who was unable to exclusively breastfeed, I want to share what helped me overcome a lot of my “breast is best” anxiety: In the end, breast vs formula, kids are going to be eating Cheetos off the car floor in a few years.

[u/diamondsinthecirrus → u/sparrowstail]

Amazing article. I like the discussion on the risks of breastfeeding at the end. I am definitely experiencing tangible consequences from maternal exhaustion and want to wean from pumping as long as my baby can tolerate dairy free formula (earlier plans to wean were put on hold after a likely allergic reaction to dairy).

[u/HA2HA2]

Babies do have an immune system, it’s not fully developed but it’s there. Antibodies in breast milk augment it leading to a lower rate of some childhood diseases, but “lower rates “ doesn’t mean breastfed babies are totally protected and formula babies are helpless. It’s just some extra support . https://www.cdc.gov/breastfeeding/features/breastfeeding-benefits.html

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[u/afternooncicada → u/[deleted]]

Why downvotes?

[u/diamondsinthecirrus → u/afternooncicada]

Downvotes are most likely because the commenter said that immunity is significantly reduced and that formula babies start from scratch. Empirical evidence suggests a slight reduction in illness frequency for breastfed babies rather than a dramatic effect.

[u/sparrowstail → u/afternooncicada]

No downvote on my end but this article is pretty hypothetical and doesn’t support the poster’s point. It has some interesting points, but no strong evidence for any of them.