Like many women, I have pale lines - scars left from where my body grew too fast and my skin didn't quite keep up. However, these are not on my tummy from pregnancy. I got my stretch marks during my teenage years. Although I did have a normally healthy diet, from what I can gather I just didn't happen to have the right vitamins at the right moment to keep my skin supple. As Piglet reaches an age where she will start growing, I have been looking into how to help her avoid teenage stretch marks.
The NHS information on stretch marks recommends Vitamins E and C, zinc and silicon in your diet to avoid stretch marks. Generally the advice is that moisturising your skin doesn't do much for stretch marks, as these are caused by tears in lower layers of skin. However, I did buy a tub of coconut oil from the health food shop; I encouraged Piglet to use it (and spread it liberally over my own skin), as it can't be bad to keep your skin supple and moisturised whatever.
At this uncertain age, with hormones raging, I feel it's good for Piglet to learn to treat her body kindly and give it a gentle rub down every couple of days. Being in touch (literally!) with her own body should help in those moments of teenage despair when she becomes convinced she is a Gorgon and ugliest kid in the universe. I will try to help out too at these times by saying things like: "I love you anyway." LOL, no, I do tell Piglet she is pretty and not to worry too much about it, just enjoy life. A laugh is worth a ton of make-up in the attracting nice friends and cool boy- or girl-friend zone. (Some of us grownups would do well to remember that!)
Information on foods in which vitamins and trace minerals are found is available from the NHS.
Vitamin E is found in nuts and seeds, and in a lot of oils (including coconut oil so I could start cooking with that as well as massaging it into my legs, although olive oil also has Vitamin E - and zinc - in it, so maybe not).
Vitamin C is found in oranges, red and orange fruit generally, broccoli and potatoes. (NB, your body does not store vit C so you need some every day. You need it to absorb iron as well so make sure you get some.)
You can get silicon from oats, barley, rice and fruit and veg.
Go to meat, fish, cheese and cereals for your zinc.
Avocados are a good source of vitamins E and C - although Piglet doesn't like avocados. However, if held in front of her nose as a possible stretch mark prevention strategy, she will give things she hasn't yet got a taste for a go.