Stella Onions, 45, said children should be weaned naturally until their baby teeth fall out to help fully develop their immune system.
She breastfeeds Josephine, five, and Zac, three, and said despite it making some people feel uncomfortable, the health benefits are vital.
"Lots of studies have been done and in general babies fed on formula are more likely to get gastric infections and urinary and respiratory problems.
"Some studies even suggest that there is an increased risk of certain childhood cancers.
"Also women who don't breastfeed have a higher risk of developing breast and ovarian cancer and rheumatoid arthritis.
"When you breastfeed your body releases a feel good hormone which calms the mother and current research is investigating if it helps with post natal depression."
Mrs Onions, from Ludlow, Shrops, said she had time to feed her children because she home schools them, and said their friends think nothing of it.
She said: ""My children's friends have seen them at my breast. They both come and ask for 'Mummy milk'. But nobody says anything bad about it.
"Nature sorts it out for you. When children lose their milk teeth between five and eight years, their jaw shape changes slightly and they lose the ability to suckle. That is when their immune system is fully developed.
"So nobody is going to be breastfeeding teenagers."
The issue of older children being breastfed was lampooned in the television show Little Britain, where a grown up man constantly demanded milk from his mother's breast.
But Mrs Onions insisted children should be weaned naturally for as long as possible.
She said: "I grew up in South Africa where the women see breasts as something to feed your children with, not something sexual.
"Some people are squeamish about it, especially in public, but you wouldn't throw a blanket over a sheep feeding a lamb in a field would you? It's what nature intended."
She has designated one breast for each child - the right one for Josephine and the left for Zac - and while they use to feed together they now drink separately.
She is now campaigning to get more mothers to breast feed and plans to launch a magazine to be distributed to ante natal clinics.
She added: "I am not trying to make mums feel guilty about not breast feeding, but you can't ignore study after study."
