Elle Macpherson on Aging: I've Learned 'It Doesn't Really Matter What I Look Like'

At 51, Elle Macpherson exudes the same confidence she had in her 20s when she was nicknamed "The Body" – but it’s taken her time to get to that happy place.

“There’s one thing being 20 and gorgeous with legs up to your armpits and beautiful tight skin,” the entrepreneur and supermodel says in a video on Australia talk show Sunrise. “And there’s another thing to be 51.”

“Finally you get to the stage and say, ‘I have been known to be one of the most beautiful women in the world and felt really not confident and sure of myself,’ ” she continues.

In addition to changing her sleeping habits and diet, the co-founder and co-owner of the premium luxury wellness business WelleCo credits her Super Elixir Alkalising Greens supplement for helping her age gracefully.

“As I’ve matured, what I’ve realized is that it doesn’t really matter what I look like, the most important thing is, ‘how do I feel?’ ” she says. “[It’s] when I started sleeping more and relaxing a little more in my life and looking after my nutrition, because good nutrition can change everything. I hadn’t really understood my body was deprived from good nutrition.”

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Macpherson recently told PEOPLE she prefers to keep her body in an alkaline state – a diet trend Kelly Ripa also favors – and even keeps a pH balance urine tester kit in her bag.

“I don’t worry about wrinkles,” she says. “I tackle internal ageing by nourishing my cells from the inside and the welcome by-product is looking and feeling good.”