Many women have straight hair, it's not a gender think, I think, maybe a bit of hormonal.
Everyone always asks me if I put something on my nails when I don't, my nails are pinkish and shine naturally.
That's because of my calcium level being high, nutrition can do a lot to your hairs and nails.
Calcium will make your nails glow (but it will take a while for them to rebuild) and about hair, I am really not sure, eat healthy, probably not too much fat and protein (proteins are actually the most poisonous nutrition to your body from the fat/carb/protein generalization) , limit fat to non-saturated and balance it with carbs (less simple, more processed)
other than that, shampoo and condition with products that fit your hair, but not daily, every other day or sometimes every third day.
Over shampooing/conditioning can do more harm than good.
I find straight hair is more common than curly hair and most people with curly hair want straight hair because it can look like a mess.
Personally I like curly hair much more and if you handle it well, you will have great looking hair