Reintroducing foods, if you decide to

Some people who adopt plant-based diets later reintroduce animal products, for health reasons, for practical reasons, during pregnancy, or because it stopped working for them.

This is discussed very little, and people going through it frequently encounter judgement rather than information.

Why people reintroduce

The reasons reported are various and mostly reasonable.

Persistent symptoms not resolved by dietary adjustment. Difficulty maintaining weight or performance. Pregnancy, where some people prefer to reduce complexity. Practical constraints — travel, illness, caring responsibilities, food access. Medical advice for a specific condition. Difficulty sustaining it socially. Or simply a change of mind.

None of these requires justification, and the ones driven by symptoms are worth investigating properly first, since most have another explanation.

Before you decide

Worth ruling out the common causes of feeling unwell, since they are frequently fixable.

Are you eating enough energy? Enough protein? Taking B12, vitamin D and iodine? Have you had blood tests? Is the diet varied, or has it narrowed?

Most people who feel worse on a plant-based diet have one of these problems rather than a fundamental incompatibility.

Our article on troubleshooting covers the sequence.

The digestive adjustment

The practical question people actually have.

After a period without animal products, reintroducing them frequently causes digestive discomfort. This is common and generally temporary.

The proposed mechanisms: changes in gut microbial composition adapted to a high-fibre plant diet; and, in the case of dairy, reduced lactase activity, since lactase production is partly use-dependent in some people.

Go slowly. Small amounts, introduced one food type at a time, with several days between.

Start with easier things. Fish and eggs are generally better tolerated initially than red meat or large quantities of dairy.

For dairy specifically: start with fermented forms — yoghurt, aged cheese — which are lower in lactose and generally better tolerated.

Small amounts repeatedly can improve tolerance over weeks for some people.

Keep the fibre. The commonest mistake is reintroducing animal products and simultaneously reducing plant foods, which loses the benefits.

Add rather than substitute.

Expect a few weeks of adjustment, as when transitioning in the other direction.

What changes nutritionally

Worth knowing so that supplements are adjusted appropriately.

B12 becomes available from food, and intake may still be marginal depending on quantity. Do not stop supplementing immediately; test.

Iron becomes more available if red meat is included, since haem iron is well absorbed.

Iodine from dairy and fish.

Omega-3 from oily fish, which addresses the conversion issue directly.

Calcium from dairy.

Fibre falls if plant foods are displaced rather than supplemented, which is worth guarding against.

Saturated fat rises depending on choices.

The partial positions

Reintroduction does not have to be total.

A great many people arrive at a position that is mostly plant-based with some animal products — described variously as flexitarian, reducetarian, or simply eating.

The evidence supports this pattern well. Cohort studies find favourable outcomes across a spectrum of reduced animal product consumption rather than only at the extreme.

Practical versions people adopt: plant-based at home and flexible when out; fish included; eggs and dairy included; animal products a few times a week; or a specific reintroduction of one food that was missed.

Each of these retains most of the health and environmental benefit.

The social and identity part

Frequently the hardest.

People who identified publicly with a dietary position, or who have advocated for it, find changing genuinely difficult — sometimes more so than the dietary change itself.

The judgement can be real. Communities built around dietary identity are sometimes unkind about people who leave them.

What is worth holding onto: a dietary decision is yours, circumstances change, and a body that is not working well is a legitimate reason to change what you feed it.

And that reducing animal product consumption substantially, sustained for decades, achieves considerably more than a strict position abandoned entirely in frustration.

If it was ethically motivated

A different consideration, and this article has nothing useful to say about the ethics.

What is worth noting practically: many people in this situation find a partial position — reducing rather than eliminating, or choosing particular products for particular reasons — more sustainable than either extreme, and consistent with what they actually believe.

The medical caveat

Where symptoms drove the decision, it is worth having them properly investigated regardless of what you decide to eat.

Fatigue, digestive symptoms and low mood have many causes, and a dietary change happening at the same time does not establish that it caused them.

General information rather than individual advice. Persistent symptoms should be investigated medically rather than addressed only through dietary change. Consult a registered dietitian for individual guidance.