Looking good is big business. But it’s not all about the latest resurfacing creams and blurring serums; having truly healthy skin, hair and nails depends on what we put into our body rather than onto it.

The best foundation is — of course — a healthy diet. But there’s also a growing range of supplements that promise to help us out. Nutritionist Cassandra Barns brings you the lowdown on six products you need in your cabinet:

Product: Solgar Skin, Nails and Hair Formula

Best for: All-round support for skin, nails and hair — for men and women

How does it work? As well as collagen-supporting nutrients such as the amino acids L-lysine and L-proline, this inexpensive all-rounder contains MSM (methylsulfonylmethane), a natural sulphur-containing compound. Sulphur is important for keratin, the protein that provides strength and structure to hair and nails and the outer layer of our skin. This product was always a favourite of my customers when I worked in a health food store.

Product: Advanced Nutrition Programme Skin Defender

Best for: Protecting against the damaging effects of the sun — ideal for summer!

How does it work? Carotenoids such as lycopene and beta-carotene found in red and orange vegetables have been found to concentrate in the skin and protect against UV damage. Skin Defender contains both of these, combined with green tea and grapeseed extract, and anti-inflammatory curcumin from turmeric. It’s not a replacement for topical sunscreen, but a great addition. I always use Skin Defender when I’m going away somewhere sunny (and a couple of weeks beforehand) for extra protection.

Product: Wellman Skin

Best for: Men’s skin health

How does it work? Wellman Skin contains vitamins and minerals to provide all-round nourishment for the skin. These are combined with plant antioxidants such as lycopene, grape seed extract and mixed carotenoids, chosen for their anti-ageing and protective properties. It’s a multivitamin and mineral too, so is a practical option for men who just want to take one supplement for multiple benefits.

Product: Viridian Clear Skin Complex

Best for: Acne or spot-prone skin in men and women

How does it work? It includes zinc, which is vital for skin healing as well as helping to balance testosterone (disrupted testosterone levels are often a factor in acne). Burdock is a herb traditionally used as a ‘blood cleanser’ and tonic for problem skins, and gotu kola can have skin-healing properties, too. I’ve recommended Clear Skin Complex to lots of people who’ve said it’s made a real difference to their skin.

Product: Imedeen Time Perfection

Best for: Women 40+, for preventing and reducing signs of skin ageing

How does it work? Imedeen supplements are based on a marine extract containing proteins said to be similar to those found in human skin. Time Perfection has been tested in a clinical trial on 74 women, finding that it performed better in improving skin moisture, clarity and texture when taken over 12 weeks, compared to a placebo.

Product: Nourkrin Woman and Nourkrin Man

Best for: Thinning hair

How does it work? The Nourkrin formulas are said to encourage and prolong the ‘growth’ phase of the hair growth cycle, reducing hair loss. In a clinical trial on 55 people, it was reported that taking Nourkrin for six months had an overall positive effect on hair growth. A caveat: with prolonged hair loss, it can be worth asking your doctor to test for other causes such as iron deficiency – especially in women.

Read more: The Grooming Guru’s guide to looking younger