When shares find favour with brokers it can often shift investor sentiment positively and give them the extra boost they need to climb higher. The good news then for shareholders of these three shares is that CommSec has recently upgraded them to consensus buy ratings. But should you invest in them?

They are as follows:

Newcrest Mining Limited (ASX: NCM)

This leading gold miner has been upgraded by brokers to a moderate buy. Whilst I am a big fan of the company, I feel an investment in Newcrest Mining comes down to your view on the direction the gold price will take in the months ahead. As markets begin to move on from the Brexit, I feel it is more likely that the price of gold will start to trend downwards rather than upwards. For this reason I would be hesitant to invest in the gold miners at present.

Navitas Limited (ASX: NVT)

The leading global education provider was upgraded by brokers to a strong buy. At a recent conference the company stated its belief that the global market place is shifting towards skilled work requirements, with low-skilled jobs facing the risk of automation. With over 120 colleges and campuses across 31 countries I believe this bodes well for the company’s long-term growth potential. Whilst I think Navitas would make a good long-term investment, I would wait for a pull back before making one. At 23x trailing earnings the shares are just a little on the expensive side in my opinion.

Sigma Pharmaceutical Limited (ASX: SIP)

The operator of the Amcal pharmacy brand was upgraded by brokers to a moderate buy at the end of last week. The company had a great fiscal 2015 which saw revenue increase by 10.2% to $3.5 billion and earnings before interest and tax grow at an even higher rate of 13.7% year-over-year to $89 million. The fact that the company is growing its earnings quicker than its revenue is great in my opinion, and I see it as an indication that management is running the company in an efficient way. But at 22x trailing earnings I believe the shares are a little on the expensive side for an investment today, especially compared to Its rival Australian Pharmaceutical Industries Ltd (ASX: API). Its shares are changing hands at just 17x trailing earnings, making it a better option for investors in my opinion.

Lastly, if you plan on investing in any of these shares I would highly recommend checking that you don't own one of these three rotten ASX shares first. Each could be doing more harm than good to your portfolio and may be best being swapped out if you ask me.

3 Rotten Shares to Sell, and 1 to Buy Today

After a double-digit rally for the ASX since 2016 lows, investors should be on high alert. You'll find a full rundown below of 3 shares we think you should avoid today plus one top pick worth buying, even if the market turns south and the RBA keeps rates at an "emergency low." Simply click here to uncover these stocks.

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Motley Fool contributor James Mickleboro has no position in any stocks mentioned. The Motley Fool Australia has no position in any of the stocks mentioned. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.